Ophthalmology – Myopic Degeneration

Basics

Description

Myopic degeneration, also called pathologic myopia or degenerative myopia, refers to progressive structural changes of the posterior segment associated with excessive axial elongation.

It can cause mild to profound central visual loss through:

• Macular atrophy
• Chorioretinal degeneration
• Lacquer cracks
• Macular hemorrhage
• Myopic choroidal neovascularization (CNV)
• Posterior staphyloma
• Myopic traction maculopathy
• Retinal detachment

Unlike ordinary refractive myopia, pathologic myopia involves progressive degenerative changes of the sclera, choroid, RPE, Bruch membrane, and retina.

Classification of Myopia

Myopia has historically been divided into:

• Simple myopia
• Congenital myopia
• Degenerative/pathologic myopia

Simple and congenital myopia do not necessarily develop the characteristic posterior degenerative changes of pathologic myopia.

Epidemiology

Myopia commonly begins during:

• Childhood
• School years
• Adolescence

In patients who develop pathologic myopia, refractive error and axial length may continue increasing well beyond adolescence.

Degenerative macular changes can begin in:

• Young adulthood
• Middle age

and may progress throughout life.

Prevalence

The prevalence of myopia varies greatly according to:

• Age
• Ethnicity
• Geographic region
• Educational exposure
• Environmental factors

Pathologic myopia is considerably less common than simple myopia but represents an important cause of irreversible visual impairment worldwide.

Risk Factors

Major risk factors include:

• High axial myopia
• Long axial length
• Progressive myopia
• Posterior staphyloma
• Increasing age
• Existing lacquer cracks
• Patchy chorioretinal atrophy
• Previous myopic CNV in the fellow eye

Genetics

Myopia is genetically complex and generally multifactorial.

Both genetic and environmental factors contribute.

Pathologic myopia does not usually follow a simple single-gene inheritance pattern, although familial clustering is common and rare monogenic forms exist.

Pathophysiology

The fundamental process is progressive axial elongation of the globe, particularly at the posterior pole.

This produces mechanical stretching and thinning of multiple ocular layers.

Scleral Changes

The posterior sclera may become:

• Thin
• Ectatic
• Structurally weakened

Progressive posterior bulging can produce:

Posterior staphyloma

which is a hallmark of pathologic myopia.

Choroidal Changes

The choroid becomes markedly thinned.

Changes include:

• Attenuation of the choriocapillaris
• Reduction of choroidal melanocytes
• Increased visibility of large choroidal vessels
• Progressive choroidal atrophy

RPE Changes

The retinal pigment epithelium becomes:

• Stretched
• Thinned
• Irregular
• Atrophic

Loss of RPE and choroidal pigmentation contributes to the classic tessellated or tigroid fundus.

Bruch Membrane Changes

Bruch membrane may undergo:

• Thinning
• Splitting
• Mechanical rupture

Linear ruptures are known as:

Lacquer cracks

These are important because they indicate severe biomechanical stress and are associated with an increased risk of myopic CNV.

Etiology

The exact cause of the degenerative process is multifactorial.

A major mechanism is thought to be:

Progressive biomechanical stretching from excessive axial elongation

leading to thinning and disruption of:

• Sclera
• Choroid
• RPE
• Bruch membrane
• Retina

Commonly Associated Conditions

High myopia may also occur in association with:

• Prematurity
• Retinopathy of prematurity
• Connective-tissue disorders
• Certain inherited retinal disorders

Premature infants may develop substantial myopia even without retinopathy of prematurity.

Diagnosis

Diagnosis is based on:

• Refractive status
• Axial length
• Characteristic fundus changes
• Multimodal imaging

History

Patients may have:

• Longstanding high myopia
• Progressive refractive change
• Gradual reduction in central vision

A patient with high myopia who develops:

• Sudden visual loss
• New metamorphopsia
• New central scotoma

should be evaluated urgently for myopic CNV or macular hemorrhage.

Ophthalmic Features

Posterior Staphyloma

A posterior staphyloma is a localized outpouching of the posterior ocular wall.

It can contribute to:

• Progressive macular distortion
• Chorioretinal atrophy
• Myopic traction maculopathy
• Macular hole
• Retinal detachment

Optic Disc Changes

Typical findings include:

• Tilted optic disc
• Oval configuration
• Peripapillary atrophy
• Temporal myopic crescent
• Disc torsion

Glaucoma evaluation can be difficult in highly myopic eyes because of altered optic-disc anatomy.

Tessellated Fundus

Thinning of the RPE and choroid makes the underlying large choroidal vessels more visible.

This produces the classic:

Tessellated or tigroid fundus

appearance.

Chorioretinal Atrophy

Progressive atrophy can appear as sharply demarcated pale areas.

It may begin as:

• Diffuse chorioretinal atrophy
• Patchy atrophy

Over time, lesions may:

• Enlarge
• Coalesce
• Involve the fovea

Foveal atrophy can cause severe irreversible central visual loss.

Lacquer Cracks

Lacquer cracks are:

Linear breaks in Bruch membrane caused by mechanical stretching.

They appear as:

• Fine yellow-white lines
• Irregular linear lesions
• Occasionally stellate lesions

They are important markers of advanced pathologic myopia.

Macular Hemorrhage

Hemorrhage may occur when a lacquer crack develops.

A hemorrhage can occur:

• Without CNV
• After relatively minor trauma
• Spontaneously

Therefore, not every macular hemorrhage in a highly myopic eye represents CNV.

Choroidal Neovascularization

Myopic CNV is one of the most important vision-threatening complications.

Clinical findings may include:

• Subretinal hemorrhage
• Gray or dark subretinal lesion
• Subretinal fluid
• Intraretinal fluid
• RPE elevation
• Sudden metamorphopsia
• Central scotoma

Fuchs Spot

After myopic CNV regresses, it may leave a pigmented fibrotic macular scar known historically as a:

Fuchs spot

This can produce permanent central visual impairment.

Myopic Maculopathy

Modern descriptions of pathologic myopia often classify macular disease according to increasing severity of:

• Tessellation
• Diffuse chorioretinal atrophy
• Patchy atrophy
• Macular atrophy

Additional “plus” lesions include:

• Lacquer cracks
• Myopic CNV
• Fuchs spot

Myopic Traction Maculopathy

Highly myopic eyes are also prone to tractional complications, including:

• Epiretinal membrane
• Vitreomacular traction
• Foveoschisis
• Retinoschisis
• Foveal detachment
• Lamellar macular hole
• Full-thickness macular hole
• Macular hole retinal detachment

These complications are particularly common in eyes with posterior staphyloma.

Peripheral Retinal Changes

High myopia is associated with increased risk of:

• Lattice degeneration
• Retinal tears
• Peripheral retinal thinning
• Rhegmatogenous retinal detachment

A careful peripheral retinal examination is therefore important.

Diagnostic Testing

Optical Coherence Tomography

OCT is essential in evaluating pathologic myopia.

It can detect:

• Myopic CNV
• Subretinal fluid
• Intraretinal fluid
• Foveoschisis
• Retinoschisis
• Macular hole
• Tractional changes
• Atrophy
• Epiretinal membranes

Serial OCT is extremely useful for treatment monitoring.

Fluorescein Angiography

Fluorescein angiography can help distinguish:

• Myopic CNV
• Simple macular hemorrhage from lacquer crack
• Areas of chorioretinal atrophy

Active CNV typically demonstrates leakage.

OCT Angiography

OCT angiography can noninvasively demonstrate abnormal neovascular networks and may be useful for:

• Detecting CNV
• Monitoring vascular activity
• Follow-up after treatment

It should be interpreted alongside structural OCT and the clinical examination.

Fundus Photography

Useful for documenting:

• Atrophy
• Lacquer cracks
• Hemorrhage
• Pigmentation
• Progressive macular changes

Axial Length Measurement

Biometry may help document:

• Excessive axial length
• Progression of axial elongation

Differential Diagnosis

Conditions that may mimic or coexist with myopic macular changes include:

• Age-related macular degeneration
• Central serous chorioretinopathy
• Inflammatory CNV
• Ocular histoplasmosis-related CNV
• Angioid streaks
• Macular dystrophy
• Traumatic choroidal rupture

Treatment

There is no treatment that reverses the underlying structural elongation once pathologic changes are established.

Management is directed toward:

• Refractive correction
• Treatment of CNV
• Management of tractional complications
• Retinal detachment treatment
• Low-vision rehabilitation

Refractive Correction

Options include:

• Spectacles
• Contact lenses

Contact lenses can provide improved optical quality in very high myopia because they reduce:

• Image minification
• Peripheral distortion

Myopic CNV Treatment

Anti-VEGF Therapy

Intravitreal anti-VEGF therapy is the current first-line treatment for myopic CNV.

Agents may include:

• Ranibizumab
• Aflibercept
• Bevacizumab

Treatment often requires fewer injections than neovascular age-related macular degeneration, although follow-up remains essential.

Historical Treatments for CNV

Older approaches included:

• Thermal laser photocoagulation
• Photodynamic therapy

These are now much less commonly used because anti-VEGF therapy generally provides better outcomes with less collateral retinal damage.

Laser treatment is particularly problematic near the fovea because scars may enlarge over time in highly myopic eyes.

Myopic Traction Maculopathy Treatment

Surgery may be considered for progressive or visually significant:

• Foveoschisis
• Macular hole
• Foveal detachment
• Vitreomacular traction
• Macular hole retinal detachment

Options may include:

• Pars plana vitrectomy
• Internal limiting membrane techniques
• Gas tamponade
• Macular buckle in selected complex cases

Management should be individualized by a vitreoretinal specialist.

Retinal Detachment

Retinal detachment may require:

• Pars plana vitrectomy
• Scleral buckle
• Pneumatic retinopexy in selected cases
• Combined procedures

Highly myopic eyes may present additional surgical challenges because of:

• Thin sclera
• Posterior staphyloma
• Long axial length
• Macular hole-associated detachment

Low-Vision Support

Patients with irreversible macular damage may benefit from:

• Magnification devices
• Electronic visual aids
• High-contrast reading material
• Lighting optimization
• Low-vision rehabilitation

Follow-Up

Patients with pathologic myopia require regular ophthalmic surveillance.

Follow-up should assess:

• Visual acuity
• Refraction
• Macula
• Optic disc
• Peripheral retina
• CNV activity
• Progressive atrophy
• Tractional macular changes

Patient Education

Patients at risk of CNV should monitor each eye separately.

They should seek prompt review for:

• New metamorphopsia
• New central blur
• New central scotoma
• Sudden reduction in vision

An Amsler grid can be used for home monitoring.

Retinal Detachment Education

Patients should also be educated about symptoms of retinal tear or detachment:

• Sudden increase in floaters
• Flashing lights
• Curtain or shadow in the visual field
• Sudden peripheral field loss

These symptoms require urgent ophthalmic assessment.

Prognosis

Visual prognosis depends on:

• Degree of posterior staphyloma
• Extent of macular atrophy
• Development of CNV
• Tractional macular disease
• Retinal detachment

Patients with progressive staphyloma and increasing macular atrophy have a guarded long-term prognosis.

The risk of vision loss generally increases with age.

Complications

Major complications include:

• Myopic CNV
• Macular hemorrhage
• Fuchs spot
• Chorioretinal atrophy
• Macular atrophy
• Myopic foveoschisis
• Macular hole
• Macular hole retinal detachment
• Rhegmatogenous retinal detachment
• Epiretinal membrane
• Glaucoma
• Progressive irreversible central visual loss

Ophthalmology Pearls

• Pathologic myopia is more than refractive error—it is a structural degenerative disease of the posterior eye.
• Progressive axial elongation causes thinning of the sclera, choroid, RPE, Bruch membrane, and retina.
• Posterior staphyloma is a hallmark of advanced disease.
• Lacquer cracks are breaks in Bruch membrane and increase the risk of myopic CNV.
• Sudden metamorphopsia or central vision loss in a highly myopic patient should raise immediate concern for CNV.
• A macular hemorrhage in high myopia can occur from a lacquer crack without CNV.
• Anti-VEGF therapy is first-line treatment for myopic CNV.
• OCT is essential for detecting both neovascular and tractional complications.
• High myopia increases the risk of retinal tears and retinal detachment, so the peripheral retina must also be examined carefully.
• Long-term surveillance is important because macular atrophy and other degenerative changes may continue to progress throughout life.