Choroidal neovascularization in high myopia

Myopic choroidal neovascularization is one of the most feared ocular complications in highly myopic patients. Dr Julien Gozlan, ophthalmic surgeon specializing in retinal diseases at the Paris – Auteuil Ophthalmology Practice, manages this macular condition using state-of-the-art diagnostic equipment including OCT and OCT angiography. This article details the pathophysiological mechanisms of myopic choroidal neovascularization, its symptoms, current diagnostic methods, treatment with anti-VEGF intravitreal injections, and long-term visual prognosis.

What is myopic choroidal neovascularization?

High myopia, or pathological myopia, is defined by an axial length exceeding 26 mm or a refractive error below -6 diopters. In these patients, progressive elongation of the eyeball causes mechanical stretching of the retina, choroid, and Bruch's membrane. When this membrane develops cracks (known as lacquer cracks or retinal stretch lines), it creates a breach that allows choroidal neovessels to proliferate beneath the retina. Myopic choroidal neovascularization, also called myopic choroidal neovascularization (myopic CNV), thus develops in the subretinal space, most commonly in a macular location, directly threatening central vision.

This complication affects approximately 5 to 11% of patients with high myopia. Unlike AMD, which occurs in elderly individuals, myopic choroidal neovascularization can appear in younger adults between 30 and 50 years of age, making it a particularly significant visual health concern. Myopic choroidal neovascularization is the leading cause of severe visual acuity loss in highly myopic individuals under 50 years of age.

Causes and risk factors of myopic choroidal neovascularization

The pathophysiology of myopic choroidal neovascularization involves several interrelated mechanisms:

• Mechanical stretching of the eyeball: progressive axial elongation weakens the posterior structures of the eye, particularly the choroid and Bruch's membrane.
• Bruch's membrane ruptures (lacquer cracks): these fissures serve as the entry point for neovessels that proliferate from the choriocapillaris into the subretinal space.
• Chorioretinal atrophy: progressive thinning of the choroid (often less than 50 µm on EDI-OCT) promotes local ischemia and the release of pro-angiogenic factors, notably Vascular Endothelial Growth Factor (VEGF).
• Posterior staphyloma: this deformation of the posterior pole worsens mechanical stress and promotes the development of myopic choroidal neovascularization.
• Genetic factors: a hereditary predisposition to pathological myopia increases the risk of neovascular complications.

The natural course without treatment is unfavorable: the neovascular membrane expands, causing subretinal hemorrhages, macular edema, and ultimately an irreversible fibrotic scar known as a Fuchs spot.

Symptoms and diagnosis of myopic choroidal neovascularization

Warning symptoms

Myopic choroidal neovascularization presents with symptoms that should prompt an urgent ophthalmology consultation:

• Sudden or rapidly progressive loss of visual acuity, especially in near vision.
• Metamorphopsia: distortion of straight lines, wavy perception of images, detectable using the Amsler grid test.
• Central scotoma: a dark or blurry spot in the center of the visual field.
• Micropsia: perception of objects as smaller than they actually are.

These symptoms, although common to other maculopathies such as macular hole or epiretinal membrane, must be addressed without delay in highly myopic patients.

Complete diagnostic workup

Diagnosis relies on a multimodal fundus examination:

1. Biomicroscopic fundus examination: visualization of a grayish or greenish lesion at the posterior pole, sometimes surrounded by a retinal hemorrhage.
2. Macular OCT (optical coherence tomography): an essential examination that reveals a hyper-reflective thickening beneath the retinal pigment epithelium or in the subretinal space, a serous retinal detachment, and assessment of choroidal thickness using EDI (Enhanced Depth Imaging) mode.
3. OCT angiography (OCTA): a non-invasive reference examination that allows direct visualization of the neovascular network without dye injection, with excellent sensitivity for detecting myopic choroidal neovascularization.
4. Fluorescein angiography: reveals early hyperfluorescence with late leakage characteristic of active neovascularization.
5. Indocyanine green angiography (ICG): useful for determining the extent and activity of the neovascular membrane, particularly in atypical cases.

Dr Julien Gozlan has a complete retinal imaging platform within his practice, enabling all of these examinations to be performed for accurate and rapid diagnosis of myopic choroidal neovascularization.

Treatment of myopic choroidal neovascularization with intravitreal injections

The standard treatment for myopic choroidal neovascularization relies on anti-VEGF intravitreal injections (IVT). This treatment has revolutionized the prognosis of this condition, which was previously responsible for legal blindness in many highly myopic patients.

Molecules used

Several anti-VEGF agents have demonstrated efficacy in the treatment of myopic choroidal neovascularization:

• Ranibizumab (Lucentis®): the first molecule to receive marketing authorization for this indication, validated by the RADIANCE study. Excellent results with a mean gain of +12 ETDRS letters at 12 months.
• Aflibercept (Eylea®): efficacy demonstrated in the MYRROR study, with a mean gain of +12 letters at 48 weeks. Approved for this indication.
• Brolucizumab (Beovu®) and faricimab (Vabysmo®): next-generation molecules currently being evaluated for use in myopic CNV.

Treatment protocol

Unlike exudative AMD, which often requires monthly injections, myopic choroidal neovascularization generally responds well to a lighter protocol:

• Loading phase: a single initial injection (unlike the 3 monthly injections for AMD), followed by reassessment at one month.
• Maintenance phase: PRN (pro re nata) strategy, meaning retreatment only in the event of recurrence documented by OCT and OCT angiography.
• Average number of injections: studies show that an average of 2 to 4 injections are needed in the first year, with fewer required in subsequent years.

This favorable response profile is explained by the typically smaller size of myopic choroidal neovascularization compared to that of AMD, and by a higher healing potential.

Visual prognosis and long-term follow-up

The visual prognosis for myopic choroidal neovascularization treated with anti-VEGF is generally favorable:

• Short term (1 year): 60 to 70% of patients gain at least 5 letters of visual acuity, and approximately 30 to 40% gain more than 15 letters.
• Medium term (2–3 years): visual gains are maintained in the majority of patients, with a decreasing number of injections.
• Long term (5 years and beyond): some patients develop progressive chorioretinal atrophy around the neovascular scar, which may secondarily limit the initial visual benefit. Regular follow-up therefore remains essential.

The most important prognostic factor is early diagnosis and treatment. Myopic choroidal neovascularization diagnosed early, before the development of extensive macular hemorrhage or fibrotic scarring, has a much better functional prognosis. Highly myopic patients should be educated about self-monitoring with the Amsler grid and should seek urgent consultation as soon as metamorphopsia appears.

Prevention and practical advice for highly myopic patients

Although there is no way to completely prevent myopic choroidal neovascularization, certain measures are recommended:

• Regular ophthalmological follow-up: annual assessment with macular OCT and dilated fundus examination for all patients with high myopia.
• Self-monitoring at home: daily use of the Amsler grid, one eye at a time, to detect metamorphopsia early.
• Emergency consultation: any change in central vision (decreased acuity, distortion, scotoma) should prompt an ophthalmology consultation within 48 hours.
• Sun protection: wearing UV-filtering lenses, although a direct link with neovascularization has not been formally established.

When should you consult Dr Julien Gozlan?

Any sudden vision loss, the appearance of metamorphopsia (distorted lines), a central scotoma, or a dark spot in the visual field in a highly myopic patient should prompt an urgent ophthalmology consultation to investigate myopic choroidal neovascularization. Patients with pathological myopia, even in the absence of symptoms, benefit from an annual assessment including macular OCT and fundus examination to detect any retinal complication early.

Further reading

• AMD: understanding age-related macular degeneration: causes, symptoms, and treatments of this maculopathy that shares common mechanisms with myopic neovascularization.
• Intravitreal injections (IVT): procedure, indications, and follow-up of anti-VEGF injections used in the treatment of choroidal neovascularization.
• OCT angiography: overview of this non-invasive examination essential for the diagnosis and monitoring of neovascular membranes.
• Macular OCT: how optical coherence tomography works and its value in the investigation of retinal diseases.