Infectious Disease and Microbiology – Coronavirus Group

Overview

Coronaviruses are enveloped, positive-sense single-stranded RNA viruses capable of causing respiratory and gastrointestinal disease. Human coronaviruses range from viruses producing mild common-cold syndromes to novel coronaviruses capable of causing severe systemic and lower respiratory tract disease.

Microbiologic Characteristics

Coronaviruses are:

• Single-stranded, positive-sense RNA viruses
• Enveloped viruses

Their surface spike glycoproteins produce the characteristic crown-like appearance responsible for the name coronavirus.

Incubation Period

For the common respiratory coronaviruses described in the source material, the incubation period is generally approximately 2–4 days.

Incubation periods vary among individual coronavirus species and syndromes.

Epidemiology

Human coronavirus infections occur worldwide.

Common human coronaviruses circulate widely and are frequent causes of respiratory infections. Transmission occurs predominantly through respiratory secretions and close contact.

Upper Respiratory Tract Infection

Common human coronaviruses frequently produce relatively mild respiratory illnesses resembling the common cold.

Clinical manifestations may include:

• Rhinorrhea
• Nasal congestion
• Sore throat
• Cough
• Headache
• Malaise
• Fever

They may also be associated with other upper respiratory manifestations, including sinusitis.

Lower Respiratory Tract Infection

Although uncommon with traditional common-cold coronaviruses, infection may occasionally progress to pneumonia in children or adults.

Lower respiratory disease is more clinically important in vulnerable populations and with the highly pathogenic novel coronaviruses.

Severe Acute Respiratory Syndrome (SARS)

A novel coronavirus was identified as the cause of severe acute respiratory syndrome (SARS).

SARS demonstrated that members of the coronavirus family can emerge from animal reservoirs and produce severe human respiratory disease with substantial outbreak potential.

Subsequent decades also saw the emergence of other clinically important coronaviruses, including the viruses responsible for MERS and COVID-19.

Gastrointestinal Disease

Coronaviruses may also be associated with gastrointestinal manifestations, including diarrhea. The degree of gastrointestinal involvement varies according to the particular coronavirus and clinical syndrome.

Diagnosis

Specific viral identification is generally unnecessary in routine uncomplicated common-cold illness, because the result usually does not change management.

When specific identification is clinically or epidemiologically important, diagnostic approaches can include:

PCR: Molecular detection is an important method for identifying specific coronaviruses.

Antigen detection: Viral antigens can be detected using appropriate assays for certain coronavirus infections.

Electron microscopy: Coronaviruses can be visualized directly by electron microscopy, although this is primarily a specialized or historical diagnostic technique rather than a routine clinical test.

Treatment

For uncomplicated infections caused by common respiratory coronaviruses, treatment is primarily symptomatic and supportive.

Management may include adequate hydration, rest, fever control, and symptomatic treatment of respiratory complaints.

Treatment of severe disease caused by specific emerging coronaviruses differs substantially and should not be generalized from treatment recommendations for common-cold coronaviruses.

Prevention

General respiratory infection prevention measures include reducing exposure to infected individuals, appropriate hand hygiene, respiratory hygiene, and improving ventilation in crowded indoor environments.

The older recommendation to simply avoid crowded places during winter months reflects the increased circulation of many respiratory viruses during colder seasons but is not a coronavirus-specific preventive strategy.

High-Yield Clinical Pattern

Enveloped virus + positive-sense single-stranded RNA + respiratory infection → think coronavirus.

Common human coronaviruses

→ Common cold / upper respiratory infection

Novel highly pathogenic coronaviruses

→ Potential severe lower respiratory disease and outbreaks

Exam Essentials

Family/group: Coronavirus

Genome: Positive-sense single-stranded RNA

Envelope: Present

Distribution: Worldwide

Common presentation: Upper respiratory tract infection/common cold

Other manifestations: Sinusitis, pneumonia, diarrhea

Historical severe syndrome: SARS

Diagnosis when indicated: PCR or antigen testing

Routine common cold: Specific coronavirus testing usually unnecessary

Treatment of uncomplicated common coronavirus infection: Supportive/symptomatic

Key clinical pearl: Coronaviruses are enveloped, positive-sense single-stranded RNA viruses whose clinical spectrum extends from the ordinary common cold to severe emerging respiratory syndromes.

→ Common cold / upper respiratory infection Novel highly pathogenic coronaviruses

→ Potential severe lower respiratory disease and outbreaks Exam Essentials Family/group: Coronavirus

Genome: Positive-sense single-stranded RNA

Envelope: Present

Distribution: Worldwide

Common presentation: Upper respiratory tract infection/common cold

Other manifestations: Sinusitis, pneumonia, diarrhea

Historical severe syndrome: SARS

Diagnosis when indicated: PCR or antigen testing

Routine common cold: Specific coronavirus testing usually unnecessary

Treatment of uncomplicated common coronavirus infection: Supportive/symptomatic Key clinical pearl: Coronaviruses are enveloped, positive-sense single-stranded RNA viruses whose clinical spectrum extends from the ordinary common cold to severe emerging respiratory syndromes.

Infectious Disease and Microbiology – Conidiobolus Species

Overview

Conidiobolus coronatus is an uncommon filamentous fungus (mold) that primarily causes a chronic granulomatous infection of the nasal and facial subcutaneous tissues. The characteristic disease is called entomophthoromycosis conidiobolae, also known as conidiobolomycosis.

Microbiologic Characteristics

Conidiobolus coronatus is a filamentous fungus with broad hyphae containing relatively few septa. Infection typically produces a chronic granulomatous tissue response rather than the rapidly invasive necrosis characteristic of some other molds.

Epidemiology

The organism is primarily encountered in tropical regions, particularly:

• Central America
• Equatorial Africa
• India

Human infection is uncommon and generally occurs following environmental exposure.

Clinical Manifestations

Entomophthoromycosis Conidiobolae

The classic presentation is a slowly progressive granulomatous infection involving the nose, mouth, and surrounding facial tissues.

Patients may develop firm subcutaneous nodules and progressive swelling of the nasal and perinasal areas. Lesions can become extremely large and cause substantial facial disfigurement.

Rare manifestations include mediastinitis and pericarditis.

Diagnosis

Diagnosis is established by demonstrating fungal elements in a tissue biopsy and by obtaining a fungal culture.

Histopathologic examination is particularly useful when evaluating a chronic granulomatous facial mass.

Treatment

Because conidiobolomycosis is rare, evidence regarding optimal treatment is limited.

Saturated potassium iodide solution has traditionally been used for cutaneous and subcutaneous disease, either alone or with trimethoprim-sulfamethoxazole (TMP-SMX).

Azole antifungals such as fluconazole or ketoconazole have also historically been reported to produce improvement, particularly in more severe disease.

Large, persistent, or markedly disfiguring lesions may require surgical management, usually in conjunction with medical therapy.

High-Yield Clinical Pattern

Tropical exposure + slowly enlarging nodular nasal/perinasal mass + chronic granulomatous inflammation → consider Conidiobolus coronatus.

Key clinical pearl: Unlike rapidly invasive fungal infections, conidiobolomycosis classically produces a chronic, slowly progressive, disfiguring rhinofacial infection.

Infectious Disease and Microbiology – Coronavirus Group

Overview

Coronaviruses are enveloped, positive-sense single-stranded RNA viruses capable of causing respiratory and gastrointestinal disease. Human coronaviruses range from viruses producing mild common-cold syndromes to novel coronaviruses capable of causing severe systemic and lower respiratory tract disease.

Microbiologic Characteristics

Coronaviruses are:

• Single-stranded, positive-sense RNA viruses
• Enveloped viruses

Their surface spike glycoproteins produce the characteristic crown-like appearance responsible for the name coronavirus.

Incubation Period

For the common respiratory coronaviruses described in the source material, the incubation period is generally approximately 2–4 days.

Incubation periods vary among individual coronavirus species and syndromes.

Epidemiology

Human coronavirus infections occur worldwide.

Common human coronaviruses circulate widely and are frequent causes of respiratory infections. Transmission occurs predominantly through respiratory secretions and close contact.

Upper Respiratory Tract Infection

Common human coronaviruses frequently produce relatively mild respiratory illnesses resembling the common cold.

Clinical manifestations may include:

• Rhinorrhea
• Nasal congestion
• Sore throat
• Cough
• Headache
• Malaise
• Fever

They may also be associated with other upper respiratory manifestations, including sinusitis.

Lower Respiratory Tract Infection

Although uncommon with traditional common-cold coronaviruses, infection may occasionally progress to pneumonia in children or adults.

Lower respiratory disease is more clinically important in vulnerable populations and with the highly pathogenic novel coronaviruses.

Severe Acute Respiratory Syndrome (SARS)

A novel coronavirus was identified as the cause of severe acute respiratory syndrome (SARS).

SARS demonstrated that members of the coronavirus family can emerge from animal reservoirs and produce severe human respiratory disease with substantial outbreak potential.

Subsequent decades also saw the emergence of other clinically important coronaviruses, including the viruses responsible for MERS and COVID-19.

Gastrointestinal Disease

Coronaviruses may also be associated with gastrointestinal manifestations, including diarrhea. The degree of gastrointestinal involvement varies according to the particular coronavirus and clinical syndrome.

Diagnosis

Specific viral identification is generally unnecessary in routine uncomplicated common-cold illness, because the result usually does not change management.

When specific identification is clinically or epidemiologically important, diagnostic approaches can include:

PCR: Molecular detection is an important method for identifying specific coronaviruses.

Antigen detection: Viral antigens can be detected using appropriate assays for certain coronavirus infections.

Electron microscopy: Coronaviruses can be visualized directly by electron microscopy, although this is primarily a specialized or historical diagnostic technique rather than a routine clinical test.

Treatment

For uncomplicated infections caused by common respiratory coronaviruses, treatment is primarily symptomatic and supportive.

Management may include adequate hydration, rest, fever control, and symptomatic treatment of respiratory complaints.

Treatment of severe disease caused by specific emerging coronaviruses differs substantially and should not be generalized from treatment recommendations for common-cold coronaviruses.

Prevention

General respiratory infection prevention measures include reducing exposure to infected individuals, appropriate hand hygiene, respiratory hygiene, and improving ventilation in crowded indoor environments.

The older recommendation to simply avoid crowded places during winter months reflects the increased circulation of many respiratory viruses during colder seasons but is not a coronavirus-specific preventive strategy.

High-Yield Clinical Pattern

Enveloped virus + positive-sense single-stranded RNA + respiratory infection → think coronavirus.

Common human coronaviruses

→ Common cold / upper respiratory infection

Novel highly pathogenic coronaviruses

→ Potential severe lower respiratory disease and outbreaks

Exam Essentials

Family/group: Coronavirus

Genome: Positive-sense single-stranded RNA

Envelope: Present

Distribution: Worldwide

Common presentation: Upper respiratory tract infection/common cold

Other manifestations: Sinusitis, pneumonia, diarrhea

Historical severe syndrome: SARS

Diagnosis when indicated: PCR or antigen testing

Routine common cold: Specific coronavirus testing usually unnecessary

Treatment of uncomplicated common coronavirus infection: Supportive/symptomatic

Key clinical pearl: Coronaviruses are enveloped, positive-sense single-stranded RNA viruses whose clinical spectrum extends from the ordinary common cold to severe emerging respiratory syndromes.

Infectious Disease and Microbiology – Coronavirus Group Overview Coronaviruses are enveloped, positive-sense single-stranded RNA viruses capable of causing respiratory and gastrointestinal disease. Human coronaviruses range from viruses producing mild common-cold syndromes to novel coronaviruses capable of causing severe systemic and lower respiratory tract disease. Microbiologic Characteristics Coronaviruses are:  Single-stranded, positive-sense RNA viruses Enveloped viruses  Their surface spike glycoproteins produce the characteristic crown-like appearance responsible for the name coronavirus. Incubation Period For the common respiratory coronaviruses described in the source material, the incubation period is generally approximately 2–4 days. Incubation periods vary among individual coronavirus species and syndromes. Epidemiology Human coronavirus infections occur worldwide. Common human coronaviruses circulate widely and are frequent causes of respiratory infections. Transmission occurs predominantly through respiratory secretions and close contact. Upper Respiratory Tract Infection Common human coronaviruses frequently produce relatively mild respiratory illnesses resembling the common cold. Clinical manifestations may include:  Rhinorrhea Nasal congestion Sore throat Cough Headache Malaise Fever  They may also be associated with other upper respiratory manifestations, including sinusitis. Lower Respiratory Tract Infection Although uncommon with traditional common-cold coronaviruses, infection may occasionally progress to pneumonia in children or adults. Lower respiratory disease is more clinically important in vulnerable populations and with the highly pathogenic novel coronaviruses. Severe Acute Respiratory Syndrome (SARS) A novel coronavirus was identified as the cause of severe acute respiratory syndrome (SARS). SARS demonstrated that members of the coronavirus family can emerge from animal reservoirs and produce severe human respiratory disease with substantial outbreak potential. Subsequent decades also saw the emergence of other clinically important coronaviruses, including the viruses responsible for MERS and COVID-19. Gastrointestinal Disease Coronaviruses may also be associated with gastrointestinal manifestations, including diarrhea. The degree of gastrointestinal involvement varies according to the particular coronavirus and clinical syndrome. Diagnosis Specific viral identification is generally unnecessary in routine uncomplicated common-cold illness, because the result usually does not change management. When specific identification is clinically or epidemiologically important, diagnostic approaches can include: PCR: Molecular detection is an important method for identifying specific coronaviruses. Antigen detection: Viral antigens can be detected using appropriate assays for certain coronavirus infections. Electron microscopy: Coronaviruses can be visualized directly by electron microscopy, although this is primarily a specialized or historical diagnostic technique rather than a routine clinical test. Treatment For uncomplicated infections caused by common respiratory coronaviruses, treatment is primarily symptomatic and supportive. Management may include adequate hydration, rest, fever control, and symptomatic treatment of respiratory complaints. Treatment of severe disease caused by specific emerging coronaviruses differs substantially and should not be generalized from treatment recommendations for common-cold coronaviruses. Prevention General respiratory infection prevention measures include reducing exposure to infected individuals, appropriate hand hygiene, respiratory hygiene, and improving ventilation in crowded indoor environments. The older recommendation to simply avoid crowded places during winter months reflects the increased circulation of many respiratory viruses during colder seasons but is not a coronavirus-specific preventive strategy. High-Yield Clinical Pattern Enveloped virus + positive-sense single-stranded RNA + respiratory infection → think coronavirus. Common human coronaviruses

→ Common cold / upper respiratory infection Novel highly pathogenic coronaviruses

→ Potential severe lower respiratory disease and outbreaks Exam Essentials Family/group: Coronavirus

Genome: Positive-sense single-stranded RNA

Envelope: Present

Distribution: Worldwide

Common presentation: Upper respiratory tract infection/common cold

Other manifestations: Sinusitis, pneumonia, diarrhea

Historical severe syndrome: SARS

Diagnosis when indicated: PCR or antigen testing

Routine common cold: Specific coronavirus testing usually unnecessary

Treatment of uncomplicated common coronavirus infection: Supportive/symptomatic Key clinical pearl: Coronaviruses are enveloped, positive-sense single-stranded RNA viruses whose clinical spectrum extends from the ordinary common cold to severe emerging respiratory syndromes.

Infectious Disease and Microbiology – Conidiobolus Species

Overview

Conidiobolus coronatus is a rare filamentous fungal pathogen that mainly causes a chronic granulomatous infection of the nasal and facial subcutaneous tissues. The disease is classically known as entomophthoromycosis conidiobolae or conidiobolomycosis.

It most often affects people living in tropical regions and typically produces slowly progressive, firm, disfiguring swelling around the nose and adjacent facial structures.

Microbiologic Characteristics

Conidiobolus coronatus is a filamentous fungus (mold).

Its hyphae are relatively broad and contain few septa. In tissue, the organism can trigger a prominent granulomatous inflammatory response.

This fungus differs from the more aggressive Mucorales because conidiobolomycosis usually progresses slowly and tends to remain localized to subcutaneous facial tissues.

Epidemiology

The infection occurs mainly in tropical and subtropical regions, especially:

• Central America

• Equatorial Africa

• India

Human infection is uncommon.

The fungus is environmental, and acquisition is thought to occur after inhalation or traumatic inoculation of fungal material into nasal or adjacent tissues.

Clinical Manifestations

Entomophthoromycosis Conidiobolae

The classic manifestation is a chronic granulomatous infection of the nose and surrounding tissues.

Patients may develop:

• Firm nasal swelling

• Subcutaneous nodules

• Thickening of perinasal tissues

• Facial distortion

• Involvement of the upper lip or adjacent oral tissues

The lesions often enlarge slowly over time and may become markedly disfiguring.

Unlike many invasive molds, tissue necrosis and rapid vascular invasion are not usually the dominant features.

Nasal and Facial Disease

The disease often begins around the nasal mucosa and extends into nearby subcutaneous tissues.

As the infection progresses, patients may develop:

• Nasal obstruction

• Facial swelling

• Firm masses

• Distortion of the nose

• Extension into the mouth or surrounding facial structures

Large lesions may interfere with breathing, eating, or normal facial function.

Mediastinitis and Pericarditis

Rarely, Conidiobolus infection can extend beyond the usual facial and subcutaneous sites.

Reported severe manifestations include:

• Mediastinitis

• Pericarditis

These forms are unusual but potentially serious.

Diagnosis

Diagnosis depends on demonstrating the fungus in affected tissue and confirming the organism by culture.

Tissue Biopsy

Biopsy can show:

• Fungal hyphae

• Granulomatous inflammation

• Characteristic inflammatory reaction around the fungal elements

Histopathology is particularly important because chronic facial swelling has a broad differential diagnosis.

Culture

Fungal culture can confirm Conidiobolus coronatus and distinguish it from other molds causing chronic subcutaneous infection.

Differential Diagnosis

Important considerations include:

• Basidiobolomycosis

• Mucormycosis

• Sporotrichosis

• Chromoblastomycosis

• Phaeohyphomycosis

• Chronic bacterial or mycobacterial infection

• Granulomatous inflammatory disease

• Neoplastic facial masses

A slowly progressive, non-necrotizing nasal or perinasal mass in a patient from a tropical region should raise suspicion for conidiobolomycosis.

Treatment

Because the disease is rare, high-quality treatment data are limited.

Potassium Iodide

A traditional treatment for cutaneous and subcutaneous disease is:

Saturated potassium iodide solution

This may be used alone or in combination with other agents.

Trimethoprim-Sulfamethoxazole

Trimethoprim-sulfamethoxazole has also been used, sometimes together with potassium iodide.

Azole Antifungals

Azoles have been reported to produce clinical improvement.

Older regimens include:

• Fluconazole

• Ketoconazole

Other systemic azoles may also be considered depending on susceptibility and clinical circumstances.

Surgical Management

Surgery may be helpful for:

• Large disfiguring lesions

• Localized masses causing functional impairment

• Disease not adequately controlled with medical therapy

Debulking or excision is usually combined with antifungal treatment rather than relied upon alone.

Prognosis

The infection usually progresses slowly and remains localized, but untreated disease can cause substantial facial deformity.

Early diagnosis and prolonged medical therapy generally improve the chance of controlling the infection and limiting disfigurement.

High-Yield Clinical Pattern

Tropical-region patient

• ●

Slowly progressive firm nasal or perinasal swelling

• ●

Large non-necrotic granulomatous facial mass

→ Think conidiobolomycosis due to Conidiobolus coronatus

Exam Essentials

Organism: Conidiobolus coronatus

Type: Filamentous fungus

Hyphae: Few septa

Geography: Tropical regions, especially Central America, equatorial Africa, and India

Classic disease: Entomophthoromycosis conidiobolae

Typical site: Nose and perinasal subcutaneous tissues

Typical lesion: Chronic nodular or granulomatous facial swelling

Major consequence: Disfiguring facial masses

Rare complications: Mediastinitis and pericarditis

Diagnosis: Tissue biopsy + fungal culture

Traditional treatment: Saturated potassium iodide

Other therapies: TMP-SMX and systemic azoles

Surgery: Useful for large or disfiguring lesions

Key clinical pearl: Conidiobolus coronatus classically causes a slowly progressive, firm, disfiguring rhinofacial subcutaneous infection in patients from tropical regions.

Medicine – Cataracts

A cataract is an opacity or clouding of the normally transparent crystalline lens of the eye. The loss of lens transparency interferes with the passage and focusing of light onto the retina, producing progressive, painless impairment of vision.

Cataracts may be congenital or acquired. Ageing is by far the most common cause, but cataracts can also occur because of genetic disorders, congenital infections, ultraviolet exposure, medications, ocular inflammation, metabolic disease, and several systemic disorders.

1. Clinical Features of Cataract

The typical presentation is gradual, painless deterioration of vision.

Patients may complain of blurred or cloudy vision, glare from bright lights, difficulty driving at night, reduced contrast sensitivity, altered colour perception, or frequent changes in their spectacle prescription.

Some patients describe halos around lights, particularly at night.

2. Red Reflex

As the lens becomes increasingly opaque, the normal red reflex may become reduced or absent.

With advanced cataract, the pupil itself may appear grey or white because the opaque lens is visible behind it.

This is particularly important in children because a white pupil or abnormal red reflex requires urgent assessment to distinguish cataract from other serious causes of leukocoria, especially retinoblastoma.

3. Congenital Cataracts

Congenital cataracts are present at birth or develop during early infancy.

They may affect one or both eyes and can result from genetic abnormalities, congenital infections, metabolic disorders, or developmental abnormalities.

Congenital cataracts are especially important because a dense cataract can prevent normal visual development and cause deprivation amblyopia.

Early detection and treatment are therefore essential.

4. Autosomal Dominant Inheritance

Inherited congenital cataracts frequently show an autosomal dominant inheritance pattern, although autosomal recessive and X-linked forms also exist.

A positive family history of childhood cataracts may therefore provide an important diagnostic clue.

The exact appearance and severity of inherited cataracts vary according to the underlying genetic abnormality.

5. Maternal Rubella Infection

Congenital rubella syndrome is a classic cause of congenital cataracts.

Maternal rubella infection, particularly during early pregnancy, can interfere with fetal eye development.

The classic congenital rubella pattern includes:

Cataracts + sensorineural deafness + congenital heart disease.

Cardiac abnormalities classically include patent ductus arteriosus and pulmonary artery stenosis.

6. CMV and Toxoplasmosis

Congenital cytomegalovirus (CMV) and congenital toxoplasmosis can produce important ocular disease.

However, cataract is much more classically associated with congenital rubella.

Congenital toxoplasmosis is particularly associated with chorioretinitis, while congenital CMV commonly causes chorioretinitis and neurological abnormalities.

Therefore, although these infections can be considered in congenital ocular disease, remember:

Rubella → classic congenital cataract association.

7. Down Syndrome

Children and adults with Down syndrome have an increased risk of several ocular abnormalities, including cataracts.

Cataracts may develop at a younger age than in the general population.

Other associated ocular problems include refractive errors, strabismus and keratoconus.

8. Age-Related Cataract

Age-related cataract, historically called senile cataract, is the most common form of cataract.

With increasing age, lens proteins undergo progressive structural and biochemical changes that reduce lens transparency.

The process is usually gradual and bilateral, although the severity may differ between the two eyes.

The modern term age-related cataract is preferred to “senile cataract.”

9. Types of Age-Related Cataract

Age-related cataracts can be classified according to the part of the lens predominantly affected.

Important patterns include:

Nuclear sclerotic cataract.

Cortical cataract.

Posterior subcapsular cataract.

Different patterns can coexist in the same patient.

10. Ultraviolet Light

Long-term exposure to ultraviolet radiation, particularly UV-B, is associated with an increased risk of cataract formation.

Chronic UV exposure contributes to oxidative and structural damage within the lens.

Appropriate UV-protective eyewear may therefore help reduce cumulative ocular ultraviolet exposure.

11. Corticosteroids

Long-term corticosteroid therapy is an important drug-related cause of cataract.

The classic pattern is a posterior subcapsular cataract.

The risk generally increases with greater cumulative steroid exposure, although susceptibility varies between individuals.

Steroids may also increase intraocular pressure and contribute to glaucoma in susceptible patients.

12. Other Drugs

Although corticosteroids are the classic examination association, several other medications can occasionally contribute to lens abnormalities.

A medication history should therefore form part of the assessment of unusually early or rapidly developing cataracts.

13. Uveitis

Chronic or recurrent uveitis can cause secondary cataract formation because persistent intraocular inflammation damages the lens environment.

The risk may be further increased because patients with significant uveitis often require prolonged corticosteroid treatment.

Therefore, cataract formation in uveitis may result from both:

Chronic inflammation + corticosteroid exposure.

14. High Myopia

High myopia is associated with an increased risk of developing cataracts and may lead to cataract formation at a younger age.

Highly myopic patients also have increased risks of other ocular complications, particularly retinal abnormalities.

15. Diabetes Mellitus

Diabetes mellitus is an important metabolic risk factor for cataract formation.

Chronic hyperglycaemia alters glucose metabolism within the lens, causing osmotic and oxidative changes that promote lens opacity.

Diabetic patients may therefore develop cataracts earlier and more rapidly than non-diabetic individuals.

16. Cushing Syndrome

Cushing syndrome can be associated with cataract formation, particularly in the context of prolonged glucocorticoid excess.

The relationship is especially relevant because exogenous corticosteroid therapy is itself a major cause of posterior subcapsular cataract.

17. Hypocalcaemia

Chronic hypocalcaemia can be associated with cataract formation.

This may occur in disorders such as hypoparathyroidism, where persistent low serum calcium contributes to abnormal lens metabolism.

Therefore:

Hypoparathyroidism → hypocalcaemia → cataracts is a useful clinical association.

18. Myotonic Dystrophy

Myotonic dystrophy has a strong association with cataracts.

The characteristic cataracts may have a distinctive multicoloured or “Christmas-tree” appearance on slit-lamp examination.

They can occur relatively early in life.

Other clues to myotonic dystrophy include myotonia, muscle weakness, frontal balding, cardiac conduction abnormalities, and endocrine manifestations.

19. Retinitis Pigmentosa

Retinitis pigmentosa is also associated with cataract formation.

The typical cataract associated with retinitis pigmentosa is a posterior subcapsular cataract.

Because RP itself progressively impairs retinal function, cataract formation can further reduce the patient’s remaining useful vision.

20. Diagnosis

Cataracts are diagnosed primarily by ophthalmological examination, particularly slit-lamp examination of the lens.

Visual acuity testing establishes the functional effect of the cataract.

The retina and optic nerve should also be assessed whenever possible because visual impairment may have more than one cause.

21. Treatment

The definitive treatment for a visually significant cataract is surgical removal of the opaque lens.

Modern cataract surgery commonly uses phacoemulsification, in which ultrasound energy fragments the cataractous lens so that it can be removed through a small incision.

An artificial intraocular lens (IOL) is then implanted to replace the focusing power of the natural lens.

22. When Is Surgery Required?

The presence of a cataract alone does not automatically require surgery.

Surgery is generally considered when the cataract causes sufficient visual impairment to interfere with daily activities, work, driving, reading, or quality of life, or when removal is necessary for another ophthalmological reason.

In children with dense congenital cataracts, treatment may need to occur urgently to allow normal visual development and prevent amblyopia.

23. Cataracts – Causes in Note Form

Congenital: inherited or developmental cataracts occurring at or shortly after birth.

Autosomal dominant: common inheritance pattern among familial congenital cataracts, although other inheritance patterns exist.

Congenital rubella: classic maternal infection associated with congenital cataracts.

CMV and toxoplasmosis: important congenital infections causing ocular disease, although cataract is much more classically associated with rubella.

Down syndrome: increased risk of cataract formation.

Ageing: the most common overall cause; modern terminology is age-related cataract.

Ultraviolet radiation: chronic exposure increases cataract risk.

Corticosteroids: classic drug association, particularly with posterior subcapsular cataracts.

Uveitis: chronic ocular inflammation can cause secondary cataracts; steroid treatment may contribute further.

High myopia: associated with increased and earlier cataract formation.

Diabetes mellitus: cataracts may develop earlier and progress more rapidly.

Cushing syndrome: glucocorticoid excess can contribute to cataract formation.

Hypocalcaemia: chronic hypocalcaemia, particularly from hypoparathyroidism, can cause cataracts.

Myotonic dystrophy: classically associated with Christmas-tree cataracts.

Retinitis pigmentosa: associated particularly with posterior subcapsular cataracts.

Key Clinical Pattern

Remember cataract as:

Progressive + painless + cloudy/blurred vision + glare + reduced red reflex.

Important examination associations are:

Congenital rubella → congenital cataracts.

Steroids → posterior subcapsular cataracts.

Diabetes → earlier cataract formation.

Uveitis → secondary cataracts.

Myotonic dystrophy → Christmas-tree cataracts.

Retinitis pigmentosa → posterior subcapsular cataracts.

And the definitive treatment for a visually significant cataract is:

Cataract extraction + intraocular lens implantation.

Medicine – Uveitis

Uveitis is inflammation involving the uveal tract of the eye, which consists of the iris, ciliary body, and choroid. Inflammation may be limited to one anatomical region or involve several parts of the eye.

Uveitis is clinically important because recurrent or severe inflammation can cause permanent visual impairment through complications such as cataract, glaucoma, macular oedema, retinal damage, or optic nerve involvement.

1. Classification of Uveitis

Uveitis is classified according to the main anatomical site of inflammation.

Anterior uveitis mainly affects the iris and anterior ciliary body and is the most common form.

Intermediate uveitis predominantly affects the vitreous and peripheral retina.

Posterior uveitis primarily involves the choroid and/or retina.

Panuveitis involves the anterior chamber, vitreous, and retina or choroid.

The underlying causes differ somewhat according to the anatomical pattern.

2. Anterior Uveitis

Anterior uveitis is often called iritis when inflammation primarily affects the iris or iridocyclitis when both the iris and ciliary body are involved.

The typical presentation is:

Painful red eye + photophobia + blurred vision.

The redness is often most prominent around the cornea, producing ciliary or circumcorneal injection.

3. Clinical Features

Patients with acute anterior uveitis commonly experience ocular pain, redness, photophobia, excessive tearing, and reduced or blurred vision.

Photophobia can be particularly prominent because movement of the inflamed iris and ciliary body causes discomfort.

Unlike acute angle-closure glaucoma, the pupil in anterior uveitis is often small or irregular, rather than fixed and mid-dilated.

4. Cells and Flare

Slit-lamp examination may demonstrate cells and flare in the anterior chamber.

Cells represent inflammatory cells circulating within the aqueous humour.

Flare results from increased protein entering the aqueous because inflammation disrupts the blood-aqueous barrier.

Therefore:

Anterior chamber cells + flare → characteristic evidence of anterior uveitis.

5. Posterior Synechiae

Inflammation can cause the posterior surface of the iris to adhere to the anterior lens capsule.

These adhesions are called posterior synechiae.

They can produce an irregular pupil and, when extensive, interfere with normal aqueous humour circulation.

This is one reason why cycloplegic/mydriatic drops are often used in anterior uveitis.

Causes of Uveitis

Uveitis has a very broad differential diagnosis. Causes include idiopathic disease, immune-mediated systemic disorders, infection, trauma, and ocular-specific inflammatory conditions.

6. Idiopathic Uveitis

A substantial proportion of patients have no identifiable systemic or infectious cause, even after appropriate investigation.

These cases are classified as idiopathic uveitis.

The extent of investigation depends on the patient’s age, anatomical type of uveitis, whether disease is unilateral or bilateral, recurrence, severity, and associated systemic features.

7. Ankylosing Spondylitis

Ankylosing spondylitis is one of the classic systemic associations with acute anterior uveitis.

The uveitis is often:

Acute + unilateral + painful + recurrent.

It is strongly associated with HLA-B27.

Some patients presenting with recurrent anterior uveitis may have previously unrecognised axial spondyloarthritis.

8. Reactive Arthritis

Reactive arthritis, formerly called Reiter syndrome, is another HLA-B27-associated spondyloarthritis that may cause ocular inflammation.

Patients may develop conjunctivitis or acute anterior uveitis.

Other features can include arthritis and urethritis or cervicitis following an appropriate gastrointestinal or genitourinary infection.

The modern term reactive arthritis is preferred over Reiter syndrome.

9. Psoriatic Disease

Psoriatic arthritis and other forms of psoriatic spondyloarthritis can be associated with uveitis.

Anterior uveitis is particularly relevant in patients with psoriatic disease who also have features of axial or HLA-B27-associated spondyloarthritis.

10. Inflammatory Bowel Disease

Both Crohn disease and ulcerative colitis can have extraintestinal ocular manifestations.

These include:

Episcleritis.

Anterior uveitis.

Uveitis does not necessarily parallel intestinal disease activity and may occasionally occur independently of a gastrointestinal flare.

11. The Spondyloarthritis Connection

An important examination pattern is the relationship between HLA-B27 spondyloarthritis and acute anterior uveitis.

Remember:

Ankylosing spondylitis → anterior uveitis.

Reactive arthritis → anterior uveitis/conjunctivitis.

Psoriatic arthritis → anterior uveitis.

IBD-associated arthritis → anterior uveitis.

These disorders belong to the broader seronegative spondyloarthritis family.

12. Sarcoidosis

Sarcoidosis is an important systemic cause of uveitis.

It can produce anterior, intermediate, posterior, or panuveitis, and ocular disease may be unilateral or bilateral.

Other clues to sarcoidosis may include pulmonary disease, bilateral hilar lymphadenopathy, erythema nodosum, lupus pernio, or other systemic manifestations.

Therefore:

Sarcoidosis + eye inflammation → think uveitis.

13. Juvenile Idiopathic Arthritis

The older term juvenile chronic arthritis has largely been replaced by juvenile idiopathic arthritis (JIA).

JIA is an important cause of chronic anterior uveitis in children.

Unlike the painful red eye of typical HLA-B27-associated acute uveitis, JIA-associated uveitis may be silent and asymptomatic, particularly early in the disease.

For this reason, children in relevant JIA risk groups require regular slit-lamp screening, even when they have no ocular symptoms.

14. Trauma

Ocular trauma can produce anterior uveal inflammation known as traumatic iritis.

It may develop following blunt trauma to the eye and cause:

Pain + photophobia + redness + blurred vision.

A history of recent ocular injury is therefore an important clue.

Infectious Causes

Infectious uveitis is particularly important to recognise because inappropriate immunosuppression without treating the infection can allow the underlying infection to worsen.

15. Tuberculosis

Tuberculosis can produce several patterns of intraocular inflammation, including posterior uveitis and choroidal disease.

Ocular TB may occur with or without obvious active pulmonary tuberculosis.

Diagnosis can be difficult and generally requires interpretation of ocular findings alongside systemic investigation and evidence of TB infection.

16. Herpes Simplex Virus

Herpes simplex virus (HSV) can cause anterior uveitis, sometimes in association with keratitis.

Herpetic anterior uveitis may be unilateral and can be associated with raised intraocular pressure.

Varicella-zoster virus is another important herpesvirus capable of producing similar ocular inflammation.

17. Toxoplasmosis

Toxoplasma gondii is a particularly important cause of posterior uveitis, specifically retinochoroiditis.

Patients may present with floaters and reduced or blurred vision.

Fundoscopy classically demonstrates an area of active retinal inflammation, sometimes adjacent to an old pigmented scar.

Therefore:

Toxoplasmosis → think posterior uveitis / retinochoroiditis.

18. Toxocariasis

Toxocara infection can cause ocular disease, particularly in children and young people.

Ocular toxocariasis can produce posterior segment inflammation and retinal granulomas, sometimes causing significant unilateral visual impairment.

It is an important infectious differential diagnosis of posterior ocular inflammation.

19. Other Important Infectious Causes

The original list is not exhaustive.

Depending on the patient’s immune status and clinical presentation, other important infectious causes include varicella-zoster virus, cytomegalovirus, syphilis, and other bacterial, viral, fungal, or parasitic infections.

CMV retinitis is particularly important in patients with severe immunosuppression.

Treatment

20. Treatment Depends on the Cause

Management depends heavily on whether the uveitis is infectious or non-infectious and on which part of the eye is involved.

For non-infectious anterior uveitis, treatment commonly includes topical corticosteroids to suppress inflammation.

21. Cycloplegic and Mydriatic Drops

Cycloplegic/mydriatic agents are often given in anterior uveitis.

They help:

Relieve pain from ciliary muscle spasm.

Prevent or break posterior synechiae.

This is an important difference from some other causes of a painful red eye.

22. Systemic Treatment

Severe, posterior, bilateral, recurrent, or systemic inflammatory uveitis may require systemic corticosteroids or steroid-sparing immunosuppressive/biologic treatment under specialist supervision.

When an underlying systemic inflammatory disease is present, treating that disease is an important part of controlling the ocular inflammation.

23. Infectious Uveitis

When uveitis is caused by infection, the underlying pathogen requires specific antimicrobial therapy.

For example, management may require anti-tuberculous therapy, antiviral therapy, or anti-Toxoplasma treatment depending on the diagnosis.

This distinction is crucial because corticosteroid treatment without appropriate antimicrobial coverage can be dangerous in some infectious forms.

24. Complications

Uveitis can cause several important complications:

Posterior synechiae.

Cataract.

Secondary glaucoma.

Cystoid macular oedema.

Retinal damage.

Optic nerve damage.

Permanent visual impairment.

Early diagnosis and adequate control of inflammation therefore matter greatly.

25. Uveitis – Causes in Note Form

Idiopathic: no underlying cause identified.

Ankylosing spondylitis: classic association with recurrent acute anterior uveitis; often HLA-B27 related.

Reactive arthritis: formerly Reiter syndrome; may cause anterior uveitis or conjunctivitis.

Psoriatic arthritis: can be associated with anterior uveitis, especially with spondyloarthritis features.

Inflammatory bowel disease: Crohn disease and ulcerative colitis can cause anterior uveitis.

Sarcoidosis: important systemic cause; can affect anterior and posterior portions of the eye.

Juvenile idiopathic arthritis: chronic anterior uveitis that may be completely asymptomatic in children.

Trauma: blunt ocular injury may produce traumatic anterior uveitis/iritis.

Tuberculosis: may cause various forms of uveitis, including posterior involvement.

HSV: may cause unilateral anterior uveitis, sometimes with keratitis and raised IOP.

Toxoplasmosis: classic infectious cause of posterior uveitis/retinochoroiditis.

Toxocariasis: may cause posterior ocular inflammation and retinal granuloma.

Key Clinical Pattern

For examination purposes, remember:

Painful red eye + photophobia + small/irregular pupil + cells and flare → anterior uveitis.

The major systemic association is:

HLA-B27 spondyloarthritis → acute anterior uveitis.

This includes:

Ankylosing spondylitis + reactive arthritis + psoriatic arthritis + IBD-associated spondyloarthritis.

Also remember:

JIA → chronic anterior uveitis that may be asymptomatic.

Sarcoidosis → uveitis.

Toxoplasmosis → posterior uveitis/retinochoroiditis.

And a useful painful-red-eye distinction:

Uveitis → photophobia + small/irregular pupil.

Acute angle-closure glaucoma → hazy cornea + mid-dilated fixed pupil + markedly raised IOP.

Scleritis → severe deep boring pain + deep violaceous scleral redness.

Medicine – Scleritis

Scleritis is a painful inflammatory disorder affecting the sclera, the dense connective tissue forming the outer coat of the eye. It is clinically important because it may indicate an underlying systemic autoimmune or vasculitic disease and, in severe cases, can threaten vision.

A substantial proportion of patients have an associated systemic disorder, although scleritis can also occur without an identifiable underlying cause.

1. Clinical Presentation

The characteristic symptom of scleritis is severe, deep ocular pain.

The pain is often described as boring or aching and may radiate to the forehead, brow, temple, or jaw. It can be worse at night and may be aggravated by eye movement.

The affected eye usually develops deep redness, and patients may also experience photophobia, tearing, and reduced vision.

2. Appearance of the Eye

Scleritis causes inflammation of the deeper episcleral and scleral vessels, producing a characteristic deep red or violaceous appearance.

The deeper vessels generally do not blanch completely with topical vasoconstrictors, which can help distinguish scleritis from more superficial episcleritis.

3. Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the classic systemic diseases associated with scleritis.

Ocular inflammation may occur in patients with longstanding or severe rheumatoid disease.

RA can also be associated with particularly destructive forms of scleral inflammation, including necrotising scleritis.

Therefore:

RA + painful red eye → consider scleritis.

4. Granulomatosis with Polyangiitis

Granulomatosis with polyangiitis (GPA), formerly called Wegener’s granulomatosis, is another particularly important association.

GPA is a systemic small- to medium-vessel vasculitis that commonly involves the respiratory tract and kidneys but may also produce significant ocular disease.

Scleritis can sometimes be an important clue to previously unrecognised systemic vasculitis.

5. Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) can be associated with scleral inflammation.

Although scleritis is less characteristic of SLE than some other ocular manifestations, a painful red eye in a patient with lupus warrants careful assessment for significant ocular inflammation.

6. Ankylosing Spondylitis

Ankylosing spondylitis and the broader group of spondyloarthritides are strongly associated with inflammatory eye disease.

However, an important distinction is that their classic ocular association is acute anterior uveitis, rather than scleritis.

Scleritis can occur in association with spondyloarthritis, but it is considerably less characteristic.

7. Inflammatory Bowel Disease

Inflammatory bowel disease, including Crohn disease and ulcerative colitis, may be associated with ocular inflammatory manifestations.

These include episcleritis and anterior uveitis, with scleritis occurring less commonly.

Nevertheless, IBD should be considered when scleritis occurs together with gastrointestinal symptoms or known inflammatory bowel disease.

8. Sarcoidosis

Sarcoidosis can involve numerous structures within the eye.

Its classic ocular manifestation is uveitis, but scleral inflammation can occasionally occur.

Therefore, sarcoidosis remains a possible systemic association of scleritis, although it is not among the most characteristic causes.

9. Infectious Scleritis

Although many cases are immune-mediated, infection must also be considered, particularly when the clinical context is atypical.

Infectious scleritis is important because treating an unrecognised infection with immunosuppression alone can worsen the disease.

10. Herpes Viruses

Both herpes simplex virus (HSV) and varicella-zoster virus (VZV) can cause infectious or infection-associated scleral inflammation.

VZV-associated disease may occur in the context of herpes zoster ophthalmicus.

Other bacterial or fungal infections may also cause infectious scleritis, particularly following ocular surgery, trauma, or other disruption of the scleral surface.

11. Types of Scleritis

Scleritis can broadly be divided into anterior and posterior disease.

Anterior scleritis is more common and can be classified into diffuse, nodular, and necrotising forms.

Necrotising disease is particularly concerning because it can cause progressive destruction and thinning of the sclera.

12. Posterior Scleritis

Posterior scleritis affects the sclera behind the equator of the globe and may therefore be less obvious on external inspection.

Patients can present with deep ocular pain, headache, reduced vision, or visual distortion.

Because the inflammation is posterior, imaging such as ocular ultrasonography may be needed to support the diagnosis.

13. Scleritis versus Episcleritis

This distinction is clinically useful.

Scleritis generally causes severe deep pain, marked tenderness and deeper violaceous redness. It has a stronger association with serious systemic autoimmune disease and may threaten vision.

Episcleritis is a more superficial inflammatory condition. It usually causes mild discomfort or irritation rather than severe pain and is generally self-limiting.

Therefore:

Very painful red eye → think scleritis rather than simple episcleritis.

14. Complications

Severe scleritis can lead to important ocular complications including scleral thinning, keratitis, uveitis, glaucoma, cataract, retinal or choroidal complications, and visual loss.

Necrotising disease carries particularly significant risk of structural ocular damage.

15. Treatment

Treatment depends on the severity and underlying cause.

Non-infectious anterior scleritis may require systemic NSAIDs, while more severe disease may require systemic corticosteroids.

Severe, recurrent, necrotising, or vasculitis-associated disease may require immunosuppressive or biologic therapy under specialist care.

If an infectious cause is identified, appropriate antimicrobial or antiviral treatment is essential rather than simply escalating immunosuppression.

16. Scleritis – Note Form

Definition: deep inflammation of the sclera.

Typical symptom: severe, deep, boring ocular pain.

Eye appearance: deep red or violaceous inflammation.

Important autoimmune association: rheumatoid arthritis.

Important vasculitic association: granulomatosis with polyangiitis (GPA; formerly Wegener’s granulomatosis).

Other autoimmune association: SLE.

Inflammatory bowel disease: associated with ocular inflammation; episcleritis and uveitis are more common, but scleritis can occur.

Ankylosing spondylitis: can be associated, although anterior uveitis is the classic ocular manifestation.

Sarcoidosis: possible association, but uveitis is more characteristic.

Infectious causes: include HSV and VZV, as well as bacterial and fungal causes in appropriate settings.

Severe form: necrotising scleritis may cause scleral destruction and is strongly associated with systemic autoimmune or vasculitic disease.

Treatment: systemic anti-inflammatory treatment or immunosuppression for non-infectious disease; targeted antimicrobial treatment when infection is responsible.

Key Clinical Pattern

Remember scleritis as:

Severe deep eye pain + deep red/violaceous eye + systemic autoimmune disease.

The two particularly important systemic associations to remember are:

Rheumatoid arthritis + GPA → scleritis.

Also remember the distinction:

Scleritis → severe pain + potentially sight-threatening.

Episcleritis → mild discomfort + usually benign.

And for examination purposes:

Ankylosing spondylitis → classically anterior uveitis.

Sarcoidosis → classically uveitis.

RA/GPA → particularly important associations with scleritis.

Medicine – Ptosis

Ptosis means drooping of the upper eyelid due to weakness or dysfunction of the structures responsible for elevating the lid, especially the levator palpebrae superioris muscle and the sympathetically supplied Müller muscle.

Ptosis may be unilateral or bilateral, congenital or acquired, and the associated neurological or ocular findings often point toward the underlying cause.

1. Unilateral Ptosis

Unilateral ptosis has a broad differential diagnosis. Important causes include congenital ptosis, third cranial nerve palsy, Horner syndrome, myasthenia gravis, eyelid masses, and idiopathic or aponeurotic causes.

2. Congenital Ptosis

Congenital ptosis is usually caused by abnormal development or dysgenesis of the levator palpebrae superioris muscle.

It is often present from birth and may affect one or both eyes, although unilateral disease is common.

If severe, the drooping eyelid can obstruct the visual axis and cause amblyopia, so children with significant ptosis require ophthalmological assessment.

3. Idiopathic or Aponeurotic Ptosis

Some patients develop ptosis without a major neurological disorder.

A common acquired mechanism is aponeurotic ptosis, in which the levator aponeurosis becomes stretched or detached, particularly with increasing age.

The eyelid crease may be elevated, and levator muscle function itself may remain relatively preserved.

4. Third Nerve Palsy

A third cranial nerve palsy can cause marked unilateral ptosis because the oculomotor nerve supplies the levator palpebrae superioris.

Associated eye movement abnormalities are usually present because the third nerve also supplies most extraocular muscles.

The classic pattern is:

Ptosis + eye positioned “down and out” + diplopia.

If parasympathetic fibres are involved, the pupil may become dilated and poorly reactive.

5. Important Third Nerve Warning Sign

A painful third nerve palsy with a dilated pupil is particularly concerning for a compressive lesion such as a posterior communicating artery aneurysm.

This requires urgent neurological assessment.

By contrast, some microvascular third nerve palsies, such as those associated with diabetes, may spare the pupil.

6. Horner Syndrome

Horner syndrome results from disruption of the sympathetic pathway supplying the eye and face.

The classic features are:

Ptosis + miosis + anhidrosis.

The ptosis is usually mild because it results from weakness of Müller muscle rather than complete levator paralysis.

The affected pupil is small because sympathetic dilator fibres are interrupted.

7. Horner Syndrome and Anisocoria

In Horner syndrome, the abnormal pupil is the smaller pupil, and the difference between the pupils is usually more obvious in the dark because the affected pupil cannot dilate normally.

This is an important distinction from third nerve palsy, in which the abnormal pupil may be dilated.

8. Myasthenia Gravis

Myasthenia gravis is an autoimmune disorder of the neuromuscular junction and is an important cause of fluctuating ptosis.

Ptosis may be unilateral or bilateral and often varies during the day.

A characteristic feature is fatigability:

Ptosis worsens with prolonged upward gaze or later in the day and improves with rest.

Diplopia may also occur because extraocular muscles are commonly involved.

9. Lid Tumour

An eyelid tumour or other mass can mechanically weigh down the upper lid and produce mechanical ptosis.

The degree of ptosis depends on the size and location of the lesion.

Examination may reveal a visible or palpable eyelid mass.

10. Bilateral Ptosis

Bilateral ptosis suggests disorders affecting the neuromuscular junction, muscles, or occasionally bilateral sympathetic pathways.

Important causes include myasthenia gravis, myotonic dystrophy, chronic progressive external ophthalmoplegia or other ocular myopathies, and rare bilateral Horner syndrome.

11. Myasthenia Gravis

Myasthenia gravis is one of the most important causes of bilateral fluctuating ptosis.

The ptosis is typically variable and fatigable and may alternate between the two eyes.

Patients may also have:

Diplopia.

Bulbar weakness.

Dysarthria or dysphagia.

Generalised limb weakness.

However, some patients have disease restricted mainly to the ocular muscles.

12. Myotonic Dystrophy

Myotonic dystrophy can cause bilateral ptosis due to progressive muscle weakness.

Other features may include:

Myotonia.

Facial weakness.

Distal muscle weakness.

Early cataracts.

Cardiac conduction abnormalities.

The overall clinical picture usually makes the diagnosis more apparent.

13. Ocular Myopathy

Primary muscle disorders can cause bilateral ptosis together with ophthalmoplegia.

An important example is chronic progressive external ophthalmoplegia, often related to mitochondrial disease.

Patients typically develop slowly progressive:

Bilateral ptosis + limitation of extraocular movements.

Unlike myasthenia gravis, the weakness is usually persistent rather than markedly fluctuating.

14. Bilateral Horner Syndrome

Bilateral Horner syndrome is rare.

It may occur in conditions affecting sympathetic pathways on both sides, including certain spinal cord lesions.

Older teaching links bilateral Horner syndrome with syringomyelia, but this is uncommon and should not be considered a typical cause of bilateral ptosis.

Syringomyelia more classically produces segmental sensory loss and can interrupt sympathetic pathways if sufficiently extensive.

15. Ptosis – Note Form

Unilateral Ptosis

Congenital ptosis: abnormal levator development, usually present from birth.

Aponeurotic/idiopathic ptosis: age-related or acquired stretching of the levator aponeurosis.

Third nerve palsy: marked ptosis with ophthalmoplegia; eye may lie “down and out.”

Third nerve pupil: may be dilated if parasympathetic fibres are involved.

Horner syndrome: mild ptosis with miosis ± anhidrosis.

Myasthenia gravis: fluctuating, fatigable ptosis that improves with rest.

Lid tumour: mechanical ptosis caused by an eyelid mass.

16. Bilateral Ptosis – Note Form

Myasthenia gravis: fluctuating and fatigable bilateral ptosis, often with diplopia.

Myotonic dystrophy: bilateral ptosis with myotonia and other muscle-system features.

Ocular myopathy: persistent bilateral ptosis with progressive ophthalmoplegia.

Bilateral Horner syndrome: rare; may occur with bilateral sympathetic pathway lesions.

17. Useful Clinical Distinctions

Third nerve palsy → ptosis + “down and out” eye ± dilated pupil.

Horner syndrome → mild ptosis + small pupil.

Myasthenia gravis → variable ptosis + fatigability + normal pupils.

Mechanical ptosis → eyelid mass or structural abnormality.

Key Clinical Pattern

When assessing ptosis, first look at the pupil and eye movements.

Ptosis + dilated pupil + ophthalmoplegia → think third nerve palsy.

Ptosis + constricted pupil → think Horner syndrome.

Fluctuating ptosis with normal pupils → think myasthenia gravis.

Bilateral slowly progressive ptosis with ophthalmoplegia → think ocular myopathy.

A particularly important emergency association is:

Painful ptosis + third nerve palsy + dilated pupil → urgently exclude a compressive intracranial aneurysm.

Medicine – Optic Neuritis

Optic neuritis is an inflammatory disorder of the optic nerve that produces acute or subacute visual impairment. It classically occurs in young adults and has an important association with multiple sclerosis (MS).

The typical presentation is unilateral visual loss developing over hours to several days, impaired colour vision, and pain that is particularly noticeable with eye movement.

1. Inflammation of the Optic Nerve

Inflammation and demyelination of the optic nerve interfere with transmission of visual signals from the retina to the brain.

The resulting visual disturbance may involve visual acuity, colour perception, contrast sensitivity, and the visual field.

2. Multiple Sclerosis

Multiple sclerosis is the classic disease associated with optic neuritis.

Optic neuritis may occur in a patient with established MS, but it can also be the first clinical manifestation of a demyelinating disorder.

For this reason, patients presenting with typical optic neuritis are assessed for evidence of demyelination elsewhere in the central nervous system.

3. Other Demyelinating Disorders

Not all demyelinating optic neuritis is caused by conventional MS.

Important modern differential diagnoses include neuromyelitis optica spectrum disorder (NMOSD), often associated with aquaporin-4 antibodies, and MOG-antibody-associated disease (MOGAD).

These disorders are important because their clinical behaviour, prognosis, and long-term treatment differ from typical MS-associated optic neuritis.

4. Infectious and Inflammatory Causes

Optic nerve inflammation can also occur in association with infections, autoimmune disease, and other inflammatory conditions.

Therefore, atypical presentations—such as bilateral severe disease, unusual age at presentation, marked optic-disc swelling, systemic symptoms, or poor recovery—should prompt investigation for alternative causes.

Clinical Features

5. Unilateral Visual Loss

Typical MS-associated optic neuritis usually causes unilateral reduction in visual acuity.

The visual loss develops relatively rapidly, generally over hours to several days, rather than occurring instantaneously.

Vision may continue to worsen for several days before stabilising and beginning to recover.

6. Reduced Colour Vision

Dyschromatopsia, or impaired colour perception, is a particularly characteristic feature.

Patients often notice that colours appear washed out or less vivid in the affected eye.

Red Desaturation

Loss of perception of red intensity is particularly useful clinically.

When comparing the two eyes, a red object may appear bright red through the unaffected eye but faded, pale, or less saturated through the affected eye.

This is known as red desaturation.

7. Pain on Eye Movement

Pain is common in typical optic neuritis and is characteristically aggravated by movement of the affected eye.

This occurs because movement of the globe can place traction on the inflamed optic nerve and surrounding tissues.

Pain may precede the visual loss or occur at approximately the same time.

8. Relative Afferent Pupillary Defect

A unilateral or asymmetrical optic neuropathy usually produces a relative afferent pupillary defect (RAPD) in the affected eye.

This can be demonstrated using the swinging flashlight test.

An RAPD is an important clinical clue that visual impairment originates from the optic nerve or severe retinal disease rather than from a simple refractive problem.

9. Central Scotoma

A central or centrocaecal scotoma is a classic visual-field abnormality in optic neuritis.

Patients may therefore have particular difficulty seeing objects directly in the centre of their visual field.

However, other patterns of visual-field loss can also occur.

10. Optic Disc Appearance

The original notes state that the optic disc is swollen, but this is not present in every patient.

In typical demyelinating optic neuritis, the optic disc often appears normal because the inflammation occurs behind the visible optic nerve head.

This is called retrobulbar neuritis.

A useful traditional description is:

“The patient sees nothing, and the doctor sees nothing.”

This refers to significant visual impairment despite a relatively normal initial fundoscopic examination.

Papillitis

In some patients, inflammation involves the visible optic nerve head and causes optic-disc swelling.

This is sometimes termed papillitis.

Therefore:

Optic neuritis → optic disc may be normal or swollen.

A normal optic disc does not exclude optic neuritis.

11. Recovery

Typical demyelinating optic neuritis generally has a good spontaneous visual prognosis.

Improvement usually begins within several weeks, and substantial recovery commonly occurs over the following weeks to months.

The older description of recovery over 2–6 weeks captures the early recovery period, although improvement may continue for considerably longer.

12. Multiple Sclerosis Risk

Optic neuritis is strongly associated with subsequent development of multiple sclerosis, but the individual risk varies considerably.

The quoted figure of 45–80% developing MS within 15 years should not be applied uniformly to every patient.

The most important predictor is the presence of demyelinating lesions on brain MRI.

A patient with multiple characteristic MRI lesions has a substantially greater future risk of MS than someone with a normal brain MRI.

Investigations

13. MRI

MRI of the brain and orbits with appropriate contrast sequences is an important investigation, particularly when assessing for demyelinating disease.

MRI may demonstrate enhancement of the affected optic nerve and can identify characteristic demyelinating lesions elsewhere in the central nervous system.

The number and distribution of brain lesions help estimate the likelihood of future or existing MS.

14. Additional Investigations

Additional testing depends on the clinical presentation.

Atypical optic neuritis may require investigation for AQP4-IgG associated NMOSD, MOG antibodies, infectious disease, systemic inflammatory disease, or other causes of optic neuropathy.

Treatment

15. Corticosteroids

High-dose corticosteroids can accelerate visual recovery in appropriate cases of acute demyelinating optic neuritis.

A traditional regimen is high-dose intravenous methylprednisolone for approximately 3 days, although modern protocols may also use appropriately dosed high-dose oral corticosteroid regimens in selected circumstances.

The exact treatment should follow specialist neurological and ophthalmological guidance.

16. Effect of Steroids on Recovery

An important distinction is that high-dose corticosteroids mainly speed the rate of visual recovery.

In typical MS-associated optic neuritis, they do not necessarily produce a major improvement in the final long-term visual acuity compared with spontaneous recovery.

Therefore, treatment decisions depend on the severity, clinical circumstances, and underlying cause.

17. Avoid Inadequate-Dose Oral Steroids Alone

Older clinical trial evidence found an increased recurrence risk with certain lower-dose oral prednisone regimens used alone.

This should not be confused with modern high-dose oral corticosteroid regimens that may achieve steroid exposure comparable to intravenous therapy.

18. Optic Neuritis – Note Form

Definition: inflammatory optic neuropathy, commonly associated with demyelination.

Classic association: multiple sclerosis.

Other important associations: NMOSD, MOG-antibody-associated disease, infections, and systemic inflammatory disorders.

Eye involvement: typical MS-associated optic neuritis is usually unilateral.

Onset: visual acuity deteriorates over hours to several days.

Pain: characteristically worse with eye movement.

Colour vision: reduced, especially red desaturation.

Visual field: central or centrocaecal scotoma is common.

Pupils: a unilateral lesion usually produces a relative afferent pupillary defect.

Optic disc: often normal in retrobulbar optic neuritis; may be swollen when the optic nerve head is involved.

Recovery: usually begins within several weeks and may continue over weeks to months.

MS risk: significant but variable; brain MRI lesions are an important predictor of future MS.

Investigation: MRI brain and orbits is particularly useful for confirming optic nerve inflammation and looking for demyelinating disease.

Treatment: high-dose corticosteroids may be used to accelerate visual recovery in appropriate cases.

Key Clinical Pattern

Remember typical optic neuritis as:

Young adult + unilateral visual loss over days + pain on eye movement + red desaturation + central scotoma + RAPD.

The optic disc may be completely normal, particularly in retrobulbar optic neuritis, so absence of disc swelling does not exclude the diagnosis.

The major association to remember is:

Optic neuritis ↔ multiple sclerosis.

MRI is especially important because demyelinating brain lesions strongly influence the patient’s future risk of MS.

Medicine – Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a group of inherited progressive retinal dystrophies in which photoreceptor cells gradually degenerate. The disease primarily affects the rods, with cone involvement occurring later in many patients.

The name is slightly misleading because RP is not primarily an inflammatory “retinitis.” It is better understood as an inherited degeneration of the retina.

1. Retinal Degeneration

In retinitis pigmentosa, there is progressive loss of photoreceptors together with characteristic pigmentary changes in the retina.

As retinal cells degenerate, pigment migrates into the retina and produces the classic bone-spicule pigmentation seen on fundoscopic examination.

Other typical retinal findings may include attenuation of retinal arterioles and a pale or waxy optic disc in more advanced disease.

2. Inheritance

Retinitis pigmentosa can follow several different inheritance patterns.

It may be:

Autosomal dominant.

Autosomal recessive.

X-linked.

There are also syndromic forms associated with systemic disease.

Because many different genes can cause RP, the age of onset, rate of progression, and severity can vary considerably between patients.

3. Rods Are Affected First

The disease predominantly affects rod photoreceptors in the early stages.

Rods are responsible mainly for vision in dim light and for much of the peripheral visual field.

This explains why the earliest symptoms are usually night blindness and progressive loss of peripheral vision.

4. Cone Involvement

As the disease progresses, cone photoreceptors may also become affected.

Cones are responsible for central visual acuity, colour vision, and vision in brighter light.

Late cone degeneration can therefore lead to loss of central vision, colour discrimination, and detailed visual acuity.

5. Night Blindness

Night blindness, or nyctalopia, is one of the earliest and most characteristic symptoms.

Patients may notice difficulty seeing in dimly lit environments, difficulty adapting when moving from bright light into darkness, or trouble navigating at night.

This occurs because rod function deteriorates before cone function.

6. Peripheral Visual-Field Loss

Loss of the peripheral visual field typically occurs before central vision is lost.

As peripheral retinal function progressively deteriorates, the visual field becomes increasingly constricted.

This eventually produces the characteristic “tunnel vision” pattern.

7. Tunnel Vision

Tunnel vision means that the patient retains a relatively narrow central area of vision while peripheral vision has been lost.

Patients may therefore have difficulty noticing objects approaching from the side, navigating unfamiliar spaces, or avoiding obstacles despite retaining relatively good central acuity early in the disease.

8. Central Vision

Central vision is often relatively preserved until later because the cones of the macula are affected after the peripheral rod system.

As cone degeneration progresses, however, central vision may decline significantly.

Complications such as cystoid macular oedema can further reduce central visual acuity.

9. Fundoscopic Findings

Classical fundoscopic features of retinitis pigmentosa include:

Bone-spicule retinal pigmentation.

Attenuated retinal vessels.

Waxy pallor of the optic disc.

These findings tend to become more obvious as the disease progresses.

10. Electroretinography

Electroretinography (ERG) can demonstrate reduced electrical responses from the retina.

Rod responses are typically reduced early, with cone responses becoming affected later.

ERG can therefore help support the diagnosis and assess the extent of generalized photoreceptor dysfunction.

11. Visual-Field Testing

Formal visual-field testing can demonstrate progressive peripheral field loss.

Ring scotomas may develop and subsequently enlarge until only a small central field remains.

This objective assessment is useful for monitoring progression and documenting functional impairment.

12. Associated Conditions

Some forms of retinitis pigmentosa occur as part of broader inherited syndromes.

An important example is Usher syndrome, in which RP is associated with sensorineural hearing loss.

Other syndromic associations can involve neurological, metabolic, renal, or skeletal abnormalities depending on the underlying genetic disorder.

13. Prognosis

Retinitis pigmentosa is usually progressive, but the rate of visual loss varies enormously between individuals and genetic subtypes.

The traditional statement that most patients are registered blind by age 40 is too absolute.

Some patients develop severe visual impairment relatively early, whereas others retain useful central vision well beyond middle age.

Therefore, prognosis should be individualised according to the specific genetic diagnosis and clinical course.

14. Treatment

There is currently no single treatment that reverses all forms of retinitis pigmentosa.

Management focuses on preserving useful vision, treating complications, providing visual rehabilitation, and identifying genetically treatable subtypes.

15. Treatment of Complications

Associated problems such as cystoid macular oedema or cataract may be treatable and can improve useful vision.

Low-vision aids, mobility training, and occupational support can also make a major difference to daily function.

16. Genetic Testing and Counselling

Because RP is genetically heterogeneous, genetic testing is increasingly important.

Identifying the causative mutation can clarify inheritance, guide family counselling, refine prognosis, and determine whether the patient may be eligible for a gene-specific therapy or clinical trial.

17. Gene Therapy

Gene therapy is available for a small subset of inherited retinal dystrophies associated with particular mutations, most notably biallelic RPE65-related retinal disease.

This does not apply to all patients with retinitis pigmentosa, but it illustrates the growing importance of precise genetic diagnosis.

18. Retinitis Pigmentosa – Note Form

Definition: inherited progressive retinal degeneration affecting photoreceptors.

Early cells affected: mainly rods.

Later cells affected: cones may become involved.

Inheritance: autosomal dominant, autosomal recessive, or X-linked.

Early symptom: night blindness.

Visual field: peripheral vision is lost first.

Typical late field defect: tunnel vision.

Fundoscopy: bone-spicule pigmentation, attenuated retinal vessels, and waxy optic-disc pallor.

Central vision: usually relatively preserved until later stages.

Investigation: visual-field testing, electroretinography, retinal imaging, and genetic testing.

Syndromic association: Usher syndrome = retinitis pigmentosa + sensorineural deafness.

Prognosis: progressive but highly variable; severe visual impairment may occur early in some patients but not universally by age 40.

Treatment: manage complications, provide low-vision support, undertake genetic counselling, and consider gene-specific therapy where applicable.

Key Clinical Pattern

Remember retinitis pigmentosa as:

Rod degeneration first → night blindness → peripheral visual-field loss → tunnel vision → later cone involvement and central visual loss.

The classic examination association is:

Night blindness + tunnel vision + bone-spicule retinal pigmentation = retinitis pigmentosa.

Medicine – Retinoblastoma

Retinoblastoma is a rare malignant tumour of the developing retina and is the most common primary intraocular malignancy of childhood. It arises from immature retinal cells following loss of normal function of the RB1 tumour-suppressor gene.

Early recognition is extremely important because retinoblastoma is potentially life-threatening, but treatment can achieve excellent survival when the disease is detected before extraocular spread.

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1. Age of Presentation

Retinoblastoma occurs almost exclusively in young children, with most cases diagnosed before the age of 5 years.

Heritable and bilateral disease tends to present particularly early, often during the first few years of life.

Therefore, the traditional association with a child younger than 3 years is a useful clinical clue, although it should not be regarded as an absolute age limit.

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2. The RB1 Tumour-Suppressor Gene

Retinoblastoma is strongly associated with abnormalities of the RB1 gene, a tumour-suppressor gene located on chromosome 13q14.

The normal RB protein helps regulate progression through the cell cycle and prevents inappropriate cellular proliferation.

When both functional copies of RB1 are lost within a retinal precursor cell, normal cell-cycle control is disrupted and a malignant tumour can develop.

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3. The Two-Hit Hypothesis

Retinoblastoma is the classic disease used to explain Knudson’s two-hit hypothesis.

Both copies of the RB1 tumour-suppressor gene must effectively be inactivated within a susceptible retinal cell for tumour formation.

However, the way these two genetic “hits” occur differs between heritable and non-heritable retinoblastoma.

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4. Heritable Retinoblastoma

In heritable retinoblastoma, the child already carries a pathogenic RB1 variant in one copy of the gene in the germline.

Therefore:

First hit → inherited or newly arising germline RB1 pathogenic variant.

A retinal cell subsequently loses or inactivates its remaining functional RB1 copy:

Second hit → somatic loss/inactivation of the remaining normal RB1 allele.

This leads to tumour formation.

Because every retinal cell already carries the first hit, several independent retinal cells may acquire a second hit.

Consequently, heritable disease is more likely to be bilateral and multifocal.

Importantly, the germline RB1 alteration may be inherited from a parent or arise de novo in the affected child, so absence of a family history does not exclude heritable disease.

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5. Non-Heritable Retinoblastoma

Not every child with retinoblastoma inherits an abnormal RB1 gene.

In non-heritable or sporadic retinoblastoma, both RB1 abnormalities generally arise somatically within the same retinal cell lineage.

Because two independent events must occur in one retinal cell, these tumours tend to occur somewhat later and are usually unilateral and unifocal.

Therefore, the original statement that all patients inherit one abnormal RB1 gene applies specifically to the heritable form, not to every retinoblastoma.

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Clinical Presentation

The classic presenting features are leukocoria, strabismus, and an abnormal or absent red reflex.

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6. White Pupil – Leukocoria

The most characteristic presentation is leukocoria, meaning a white pupillary reflex.

Instead of the normal reddish-orange reflection seen when light enters the pupil, the affected eye may show a white reflection because light is reflected from the retinal tumour.

Parents sometimes first notice leukocoria in a flash photograph, where one pupil appears white rather than showing the expected red reflex.

Leukocoria in a child requires urgent ophthalmological assessment.

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7. Squint – Strabismus

Strabismus, or squint, is another important presentation.

The affected eye may deviate because the tumour interferes with central vision, preventing normal binocular visual alignment.

A new unexplained squint in a young child therefore requires proper ocular assessment rather than being assumed to be benign.

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8. Loss of the Red Reflex

A normal eye produces a symmetrical red reflex when examined with an ophthalmoscope.

Retinoblastoma may replace this normal reflex with an abnormal, reduced, asymmetric, or white reflex.

The red-reflex examination is therefore an important part of evaluating infants and young children.

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9. Other Presentations

More advanced retinoblastoma can occasionally cause reduced vision, a red or painful eye, glaucoma, or enlargement/protrusion of the eye.

These presentations generally suggest more advanced intraocular disease and are less desirable than detecting the tumour at the leukocoria stage.

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10. Diagnosis

A child suspected of having retinoblastoma requires urgent specialist ophthalmological assessment.

Detailed examination of the retina, often under anaesthesia in young children, is central to diagnosis.

Imaging such as ocular ultrasonography and MRI can help assess the tumour and determine whether there is involvement of structures such as the optic nerve or central nervous system.

MRI is particularly useful because it avoids unnecessary ionising radiation, which is especially relevant in children with germline RB1 abnormalities.

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11. Treatment

Treatment depends on whether disease is unilateral or bilateral, the size and location of the tumour, whether vision can be preserved, and whether disease has spread beyond the eye.

Modern treatment aims first to save the child’s life, then whenever possible to preserve the eye and useful vision.

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12. Local Treatment

Small tumours may sometimes be treated with local therapies such as laser treatment or cryotherapy.

These approaches destroy tumour tissue while attempting to preserve surrounding ocular structures.

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13. Chemotherapy

Chemotherapy may be used to shrink or control retinoblastoma.

Modern specialist treatment may involve systemic chemotherapy, intra-arterial chemotherapy delivered through the ophthalmic artery, or intravitreal chemotherapy depending on the pattern and extent of disease.

These techniques have improved the ability to preserve affected eyes in selected children.

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14. Enucleation

Enucleation, or surgical removal of the affected eye, may be required for a large advanced tumour when useful vision cannot be preserved or when the tumour presents a significant risk of extraocular spread.

Although eye preservation is desirable, control of potentially fatal malignancy remains the priority.

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15. Association with Osteosarcoma

Children with heritable RB1-related retinoblastoma have an increased lifetime risk of developing second primary malignancies.

One of the classic associations is osteosarcoma.

The underlying germline RB1 abnormality predisposes cells elsewhere in the body to malignant transformation, explaining why the cancer risk extends beyond the retina.

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16. Other Second Malignancies

The increased risk is not limited to osteosarcoma.

Patients with heritable retinoblastoma may also have an increased risk of other malignancies, including soft-tissue sarcomas and melanoma, among others.

Historically, radiotherapy could further increase the risk of subsequent malignancy, particularly in genetically susceptible patients.

Long-term surveillance is therefore important.

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17. Retinoblastoma – Note Form

Definition: malignant tumour arising from the retina in young children.

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Typical age: usually presents in early childhood, commonly before 5 years and often before 3 years.

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Gene: associated with loss of the RB1 tumour-suppressor gene on chromosome 13q14.

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Mechanism: both functional copies of RB1 must be inactivated—the classic two-hit hypothesis.

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Heritable disease: one RB1 pathogenic variant is already present in the germline, followed by somatic loss of the remaining functional allele.

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Pattern of heritable disease: tends to present earlier and is more likely to be bilateral and multifocal.

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Sporadic/non-heritable disease: both RB1 hits usually occur somatically within retinal cells.

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Pattern of sporadic disease: more commonly unilateral and unifocal.

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Most characteristic presentation: leukocoria—a white pupillary reflex.

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Other important presentation: strabismus (squint).

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Red reflex: may be absent, asymmetric, abnormal, or replaced by a white reflex.

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Treatment: specialist therapy may include local laser/cryotherapy, chemotherapy, and enucleation for selected advanced tumours.

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Important association: patients with heritable RB1 disease have an increased risk of subsequent malignancies, classically osteosarcoma.

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Key Clinical Pattern

Think of retinoblastoma when a very young child develops:

White pupil (leukocoria) + abnormal/lost red reflex ± squint.

The genetics can be remembered as:

RB1 tumour suppressor → two hits required → loss of both functional copies → retinoblastoma.

Heritable disease already has the first RB1 hit in the germline, making early, bilateral, or multifocal tumours more likely and increasing the lifetime risk of other malignancies, particularly osteosarcoma.

The most important examination association is:

Child + leukocoria → retinoblastoma must be urgently excluded.