High myopia is no longer just a refractive condition — it is increasingly being recognized as a vision-threatening disease, particularly when structural changes develop at the level of the posterior pole. One of the most concerning complications of high axial myopia is Myopic Macular Degeneration (MMD), a form of progressive degeneration that can result in irreversible central vision loss.
In this article, we explore how to identify, investigate, and manage the spectrum of retinal changes in pathologic myopia — with a special focus on choroidal neovascularisation (CNV) and myopic foveoschisis.
📖 What Is Pathologic Myopia?
Pathologic or degenerative myopia is defined by the presence of structural changes in the posterior segment of highly myopic eyes. Clinically, it is seen in individuals with a spherical equivalent greater than -8.00 D or an axial length exceeding 32.5 mm. These changes often progress silently and may only become symptomatic once irreversible damage has occurred at the macula.
🔍 Clinical Clues on Examination
The classic fundus findings in myopic macular degeneration include:
- Tilted optic discs
- Temporal peripapillary atrophy
- Diffuse or patchy chorioretinal atrophy — areas where choroidal vessels become prominently visible
- Lacquer cracks — fine, yellowish linear ruptures of Bruch’s membrane
- Posterior staphyloma — a localized outward protrusion of the posterior globe, best seen on B-scan or OCT
- Macular CNV, often associated with subretinal hemorrhage or a pigmented Forster-Fuchs spot
- In some cases, there may be macular holes or myopic foveoschisis, with splitting of retinal layers
Ophthalmoscopy or slit-lamp biomicroscopy can raise clinical suspicion, but OCT and angiographic imaging are vital for accurate characterization.
🔬 Investigating Myopic Macular Changes
Refraction provides a baseline, but is rarely sufficient for posterior segment evaluation. Additional investigations include:
- OCT (Optical Coherence Tomography):
Critical for identifying posterior staphyloma, myopic foveoschisis, subretinal fluid, and early macular holes. It can also differentiate true CNV from other macular pathologies. - B-scan ultrasonography:
Helpful when media are hazy or when posterior staphyloma is suspected but not clearly visible. - FFA (Fundus Fluorescein Angiography):
Used particularly in suspected CNV, revealing classic leakage patterns and delineating lesion boundaries.
💊 Managing Myopic CNV and Foveoschisis
🌱 Choroidal Neovascularisation
The development of CNV in a highly myopic eye can rapidly lead to central vision loss. Prompt intervention is critical.
Anti-VEGF Therapy is now the first-line treatment:
- Ranibizumab (Lucentis) is supported by NICE Guidance and demonstrated superior outcomes in the RADIANCE study, where patients had significantly better ETDRS letter gain compared to photodynamic therapy (vPDT) at 3 months.
- Aflibercept (Eylea) is another effective option endorsed by NICE Guidance. The MYRROR study showed a +12.1 letter gain at 24 weeks with aflibercept versus -2 letters in the sham group.
Laser photocoagulation is now largely obsolete and only considered in rare cases of extrafoveal CNV.
🧪 Myopic Foveoschisis
This is characterized by splitting of retinal layers in the macular region, often seen in eyes with posterior staphyloma. OCT shows typical bridging columns and schitic cavities.
- If foveal detachment is evident, early surgical intervention (usually within 1–2 months) is recommended to prevent macular hole formation.
- If schisis is present without foveal involvement, observation is the preferred approach, as surgery is not indicated in the absence of detachment.
📊 Myopia Subtypes and Associations
Definitions
| Term | Definition |
|---|---|
| High Myopia | ≥ -6.00 D or axial length ≥ 26.5 mm |
| Pathologic Myopia | > -8.00 D or axial length > 32.5 mm with degenerative fundus changes |
Systemic Associations
| Category | Associated Conditions |
|---|---|
| Connective Tissue Disorders | Stickler syndrome, Marfan syndrome, Ehlers-Danlos |
| Infectious | Congenital rubella |
| Chorioretinal Dystrophies | Gyrate atrophy |
| Others | Albinism, Down syndrome |
Patients with these systemic associations often present with early or severe myopia and should be monitored closely for posterior segment complications.
🧠 FRCOphth Tip
In exams, when asked about complications of high myopia, always mention:
- Posterior staphyloma
- Myopic CNV
- Foveoschisis and macular hole formation
- Retinal detachment
- Associated syndromes and systemic conditions
In the context of CNV, quoting key studies like RADIANCE and MYRROR, and referencing NICE guidance strengthens your answer.