Ophthalmology – Trachoma

What the Disease Represents

Trachoma is a chronic keratoconjunctivitis caused by repeated ocular infection with:

Chlamydia trachomatis serovars A, B, Ba, and C.

It remains an important preventable cause of blindness in some endemic communities.

The disease has two broad phases:

• Active inflammatory trachoma, mainly affecting young children
• Cicatricial trachoma, developing years later after repeated infections

The sight-threatening sequence is:

Recurrent conjunctival infection → tarsal scarring → entropion/trichiasis → repeated corneal trauma → corneal opacity → blindness

Where Trachoma Persists Today

The global burden has fallen substantially because of large-scale control programs.

Trachoma now persists mainly in communities with:

• Poverty
• Limited access to clean water
• Poor sanitation
• Household crowding
• Inadequate access to eye care

The greatest remaining burden is concentrated predominantly in parts of:

• Sub-Saharan Africa
• Some areas of the Middle East
• Selected regions of Asia and the Pacific

Many countries that were historically endemic have now achieved elimination of trachoma as a public health problem.

Who Is Most Affected

Active Trachoma

Most common in:

Children approximately 1–9 years old

Young children act as an important reservoir of ocular infection.

Cicatricial Disease

Scarring and trichiasis are more common in:

• Adults
• Older individuals
• Women in endemic communities

Women may have greater cumulative exposure because of close contact with infected children.

How Infection Spreads

Transmission occurs through infected ocular or nasal secretions.

Important routes include:

• Direct eye-to-hand-to-eye contact
• Contaminated fingers
• Shared towels or cloths
• Fomites
• Eye-seeking flies, particularly Musca sorbens

Respiratory spread through coughing or sneezing is not considered a major transmission pathway.

Why Sanitation Matters

Eye-seeking flies breed particularly well where there is:

Exposed human feces.

Therefore:

• Latrine access
• Waste disposal
• Facial cleanliness
• Water availability

are central components of trachoma control.

How Repeated Infection Produces Blindness

A single infection usually does not cause blindness.

The problem is:

Repeated episodes of conjunctival infection and inflammation over many years.

This produces:

1. Chronic follicular conjunctivitis
2. Subepithelial fibrosis
3. Tarsal conjunctival scarring
4. Eyelid distortion
5. Entropion
6. Trichiasis
7. Repeated corneal epithelial injury
8. Secondary infection and vascularization
9. Permanent corneal opacity

What Happens Microscopically

Active disease shows:

• Chlamydial infection of conjunctival epithelial cells
• Lymphoid follicles
• Chronic inflammatory-cell infiltration

Repeated inflammation produces:

• Goblet-cell loss
• Squamous metaplasia
• Subepithelial fibrosis
• Conjunctival shortening

This eventually transforms an infectious conjunctivitis into a:

Cicatrizing ocular-surface disease.

The WHO Simplified Grading System

Trachoma is commonly classified clinically using five signs:

TF, TI, TS, TT, and CO

TF – Trachomatous Inflammation, Follicular

Defined by:

Five or more follicles, each at least 0.5 mm, in the central upper tarsal conjunctiva.

This is the principal clinical sign used in population surveys of active trachoma.

TI – Trachomatous Inflammation, Intense

There is pronounced inflammatory thickening of the upper tarsal conjunctiva such that:

More than half of the normal deep tarsal vessels are obscured.

TI reflects more severe active inflammatory disease.

TS – Trachomatous Scarring

The tarsal conjunctiva develops visible:

• White bands
• Fibrous lines
• Sheets of scar tissue

A classic horizontal scar is:

Arlt line.

Scarring indicates prior repeated inflammation rather than active infection itself.

TT – Trachomatous Trichiasis

Defined clinically by:

At least one eyelash touching the globe or evidence of recent removal of in-turned lashes.

This is the key sight-threatening stage because lashes repeatedly abrade the cornea.

CO – Corneal Opacity

There is corneal scarring severe enough to:

Obscure part of the pupil margin.

This represents advanced disease and is the major cause of irreversible visual loss.

Classic Conjunctival Findings

Active disease most characteristically affects the:

Upper tarsal conjunctiva.

Findings may include:

• Follicles
• Papillary hypertrophy
• Conjunctival thickening
• Hyperemia

Repeated episodes eventually produce:

• Fibrosis
• Foreshortening
• Lid distortion

Herbert Pits

Herbert pits are small depressions at the superior limbus produced by healed limbal follicles.

They are:

• Evidence of previous trachomatous inflammation
• Characteristic of established disease

but are not required for diagnosis.

Corneal Pannus

Active or chronic trachoma may produce:

Superficial corneal vascularization and infiltration, particularly from the superior limbus.

This is termed:

Trachomatous pannus.

Advanced pannus and repeated lash trauma may contribute to corneal scarring.

Arlt Line

An Arlt line is a horizontal band of scar tissue across the upper tarsal conjunctiva.

It is a classic sign of:

Chronic cicatricial trachoma.

How Patients Present During Active Disease

Children may be:

Asymptomatic

or have:

• Mild redness
• Tearing
• Mucous discharge
• Irritation
• Itching
• Foreign-body sensation

The relatively mild symptoms help explain why infection can circulate extensively within communities.

How Adults With Late Disease Present

Patients with trichiasis may report:

• Foreign-body sensation
• Tearing
• Photophobia
• Ocular pain
• Reduced vision

Symptoms frequently reflect:

Mechanical lash-cornea contact rather than ongoing Chlamydia infection.

How the Diagnosis Is Usually Made

In endemic settings, trachoma is primarily a:

Clinical diagnosis

using the characteristic upper tarsal conjunctival and eyelid findings.

Laboratory testing is generally unnecessary for routine individual diagnosis.

Role of PCR

Nucleic-acid amplification testing can detect:

C. trachomatis DNA

from conjunctival specimens.

PCR is most useful for:

• Research
• Surveillance
• Programmatic assessment
• Unusual diagnostic situations

Clinical signs and active infection do not always correlate perfectly because inflammation may persist after organisms have disappeared.

Why Older Cytology Tests Are Less Important

Historical testing included:

• Giemsa staining for inclusions
• Direct fluorescent antibody testing
• Enzyme immunoassay

These have largely been replaced by:

Nucleic-acid amplification methods

when laboratory confirmation is required.

Important Diagnostic Alternatives in Active Disease

Consider:

• Adenoviral conjunctivitis
• Adult inclusion conjunctivitis
• Bacterial conjunctivitis
• Toxic medicamentosa
• Molluscum-associated conjunctivitis
• Allergic follicular conjunctivitis

Trachoma vs Adult Inclusion Conjunctivitis

This distinction is important.

Trachoma

Caused by:

C. trachomatis A, B, Ba, C

and associated with endemic community transmission and chronic scarring.

Adult Inclusion Conjunctivitis

Usually caused by:

C. trachomatis D–K

and is typically sexually acquired.

Adult inclusion conjunctivitis generally does not produce the classic community-level blinding cicatricial disease of endemic trachoma.

Cicatricial Disease Differential

Other causes of conjunctival scarring and trichiasis include:

• Mucous membrane pemphigoid
• Stevens–Johnson syndrome
• Toxic epidermal necrolysis
• Chemical injury
• Severe chronic blepharoconjunctivitis
• Prior ocular surgery or trauma

The epidemiologic history and classic tarsal pattern are important.

The SAFE Strategy

The cornerstone of global trachoma control remains the WHO:

SAFE strategy

which stands for:

S – Surgery for trichiasis

A – Antibiotics to reduce ocular C. trachomatis infection

F – Facial cleanliness

E – Environmental improvement

Each component addresses a different stage of the disease.

S – Surgery for Trachomatous Trichiasis

Patients with lashes touching the globe require:

Prompt eyelid treatment

because continued lash trauma can permanently scar the cornea.

Common procedures include:

• Bilamellar tarsal rotation
• Posterior lamellar tarsal rotation

The surgical goal is to rotate the eyelid margin outward and prevent lashes from contacting the cornea.

Why Epilation Is Not Definitive Treatment

Temporary epilation can reduce corneal trauma when surgery is not immediately available.

However:

Repeated lash plucking does not correct the underlying entropion.

Definitive lid surgery is preferred for significant trachomatous trichiasis.

A – Antibiotic Treatment

The preferred antibiotic for active trachoma and population control is usually:

Oral azithromycin

A commonly used single-dose regimen is:

• Adults: 1 g orally once
• Children: 20 mg/kg orally once, up to the adult maximum

Exact programmatic dosing follows local or WHO protocols.

Alternative Antibiotic Therapy

When azithromycin cannot be used, an established alternative is:

Topical tetracycline 1% ophthalmic ointment twice daily for 6 weeks.

This prolonged topical course is less convenient, which is why azithromycin is generally favored.

Important Modern Correction About Doxycycline

Older sources sometimes listed short oral doxycycline courses as routine trachoma therapy.

For endemic trachoma control:

Single-dose azithromycin or topical tetracycline remains the standard programmatic approach.

Doxycycline is not the usual first-line population treatment.

Why Community Treatment Is Necessary

Treating one symptomatic child is often insufficient because infection circulates throughout:

• Families
• Households
• Villages

In endemic districts, antibiotic programs may therefore involve:

Mass drug administration (MDA).

How Mass Azithromycin Programs Work

Communities above programmatic prevalence thresholds may receive:

Annual mass azithromycin treatment

for multiple years.

Repeat surveys determine whether:

• Additional rounds are required
• Transmission has fallen sufficiently

The exact schedule depends on local prevalence and elimination-program criteria rather than a fixed universal number of treatments.

F – Facial Cleanliness

Regular cleaning of children’s faces reduces:

• Ocular discharge
• Nasal secretions
• Fly attraction
• Opportunity for person-to-person transmission

Children with persistently dirty faces are more likely to sustain community transmission.

E – Environmental Improvement

Important measures include:

• Access to clean water
• Household latrines
• Proper disposal of feces
• Reduced household crowding
• Improved sanitation
• Fly control where relevant

Antibiotics alone cannot provide durable elimination when transmission conditions persist.

When Trachoma Is Considered Eliminated as a Public Health Problem

Modern elimination programs assess population-level indicators including very low prevalence of:

• Trachomatous inflammation–follicular in young children
• Trachomatous trichiasis in adults that remains unknown to the health system

Countries must also demonstrate the capacity to identify and manage new trichiasis cases.

Elimination does not mean the organism has disappeared completely; it means the blinding public-health burden has fallen below defined thresholds.

Managing Corneal Surface Disease

Patients with trichiasis-related epithelial injury may require:

• Lubricating drops
• Ointment
• Treatment of secondary bacterial infection when present

However, lubrication does not replace:

Correction of the lid abnormality.

Corneal Transplantation

Advanced central corneal opacity may occasionally require:

• Penetrating keratoplasty
• Selected other corneal rehabilitation

However, prognosis may be limited by:

• Severe ocular-surface disease
• Corneal vascularization
• Dry eye
• Persistent lid abnormality

Any trichiasis or entropion should be corrected:

Before considering corneal transplantation.

Dry Eye in Cicatricial Trachoma

Chronic conjunctival scarring can destroy:

• Goblet cells
• Accessory lacrimal structures

leading to:

Chronic ocular-surface dryness.

This may further contribute to epithelial instability and corneal damage.

Why Women Often Carry More Late Disease

Women in endemic communities often have greater cumulative exposure to infected young children.

Consequently, they may experience:

• More repeated infections
• More conjunctival scarring
• Greater risk of trichiasis

The increased late burden is therefore largely related to:

Exposure patterns rather than an intrinsic sex-specific ocular susceptibility.

Preventing Progression to Blindness

The most important interventions are:

• Reduce childhood transmission
• Treat endemic infection at community level
• Identify trichiasis early
• Operate before irreversible central corneal scarring develops

Once dense central corneal opacity occurs, antibiotic treatment cannot restore transparency.

Follow-Up After Trichiasis Surgery

Patients require follow-up for:

• Recurrent trichiasis
• Eyelid contour abnormality
• Corneal healing
• Persistent entropion
• Overcorrection

Recurrence can occur even after technically successful surgery.

Expected Clinical Course

Repeated infection in childhood may produce progressively more conjunctival fibrosis.

The cicatricial consequences may not become clinically important until:

Years or decades later.

Thus adults with trichiasis may no longer have active Chlamydia infection.

Major Causes of Vision Loss

Visual impairment primarily results from:

• Trichiasis-induced corneal abrasion
• Recurrent microbial keratitis
• Corneal vascularization
• Chronic ocular-surface disease
• Dense corneal scarring

The optic nerve and retina are not the principal targets.

High-Yield Takeaways

• Trachoma is a chronic keratoconjunctivitis caused by Chlamydia trachomatis serovars A, B, Ba, and C.
• Blindness results not from a single infection but from recurrent childhood infection causing progressive conjunctival scarring, entropion, trichiasis, and corneal opacity.
• Active disease predominantly affects young children, while cicatricial trichiasis and blindness appear mainly in adults.
• Transmission occurs primarily through hands, ocular/nasal secretions, fomites, and eye-seeking flies; coughing and sneezing are not major routes.
• The WHO simplified grading system is TF, TI, TS, TT, CO.
• TF = ≥5 follicles ≥0.5 mm on the central upper tarsal conjunctiva.
• TI = intense tarsal inflammation obscuring more than half of deep conjunctival vessels.
• TS = visible tarsal conjunctival scarring.
• TT = at least one lash touching the globe or evidence of recent epilation.
• CO = corneal opacity involving the pupil margin.
• Classic late signs include Arlt lines, Herbert pits, entropion, trichiasis, and superior corneal pannus.
• Laboratory confirmation is usually unnecessary clinically; PCR is mainly used for surveillance, research, or selected uncertain cases.
• The global control strategy remains SAFE: Surgery, Antibiotics, Facial cleanliness, Environmental improvement.
• Single-dose oral azithromycin is the preferred antibiotic for active disease and mass treatment programs; topical tetracycline 1% twice daily for 6 weeks is an alternative.
• Community antibiotic administration is guided by local prevalence, not simply by treatment of symptomatic individuals.
• Trichiasis surgery is the key sight-saving intervention once cicatricial lid disease develops.
• Epilation may provide temporary relief but does not correct the underlying entropion.
• Corneal transplantation has a guarded prognosis when there is severe vascularization or ocular-surface scarring and should only be considered after eyelid abnormalities are corrected.
• Sustained elimination depends on both antibiotics and improvements in water access, facial hygiene, sanitation, and environmental conditions.
• Trachoma is increasingly being eliminated as a public-health problem in many countries, but it remains a preventable cause of blindness in several endemic regions.