Myopic degeneration is a serious eye condition that can lead to vision loss, distinct from common nearsightedness. Also known as pathologic myopia or degenerative myopia, it affects individuals with severe nearsightedness, characterized by a high refractive error or an elongated eyeball. While common, myopic degeneration involves specific structural changes that can result in permanent vision impairment. This condition impacts approximately 3% of the global population.
The Link Between High Myopia and Degeneration
Severe nearsightedness, or high myopia, is defined as a refractive error of -6.00 diopters or more, or an eye with an axial length of 26.5 mm or greater. In such cases, the eyeball elongates beyond its typical spherical shape. This excessive axial length causes the various layers of the eye, including the retina, choroid, and sclera, to stretch and become thinner.
Like stretching a balloon too far, the material becomes taut and fragile. The stretching in the eye can lead to tears and damage within these delicate tissues. Specific changes include posterior staphyloma, an outpouching of the ocular wall, and lacquer cracks, which are irregular yellow bands representing breaks in Bruch’s membrane. These structural alterations differentiate pathological myopia from simple myopia, where the eye is nearsighted but lacks these degenerative changes.
Identifying the Signs and Symptoms
Patients with myopic degeneration may experience various vision changes as the condition progresses. Common symptoms include:
Gradual or sudden worsening of vision, even with corrective lenses, where clarity may not be fully restored.
New or an increase in existing floaters, which are small dark specks or cobweb-like shapes drifting across the visual field.
Flashes of light, known as photopsia, indicating stress or changes in the retina.
Distorted or wavy vision, termed metamorphopsia, where straight lines appear bent or curvy.
Blind spots, or scotomas, particularly near the center of vision, making tasks like reading or recognizing faces challenging.
An Amsler grid, a simple square grid with a central dot, can be used at home to monitor for these distortions or missing areas in the central visual field.
Diagnosis and Monitoring
An eye care professional confirms myopic degeneration through a comprehensive dilated eye exam. During this examination, the doctor looks for specific signs such as changes in the macula’s shape, thinning or bleeding in the retina, or indications of layer separation. Visual acuity testing assesses the clarity of vision, while ophthalmoscopy directly examines the retina for signs of degeneration.
Advanced imaging technologies provide more detailed insights into the eye’s internal structures. Optical Coherence Tomography (OCT) is a non-invasive test that produces cross-sectional images of the retina, helping to detect thinning, fluid accumulation, or other structural changes. Fluorescein angiography involves injecting a dye into the bloodstream to highlight abnormal blood vessel growth, such as choroidal neovascularization (CNV), or leakage within the retina. Regular monitoring with these tools is important to detect early complications and manage the progressive nature of the condition.
Treatment and Management Strategies
Treatment for myopic degeneration primarily targets complications rather than the underlying myopia itself. A major focus is on choroidal neovascularization (CNV), where abnormal, fragile blood vessels grow under the retina and can leak fluid or blood, leading to vision loss. The first-line treatment for myopic CNV involves anti-VEGF (anti-vascular endothelial growth factor) injections directly into the eye. These medications, such as ranibizumab and aflibercept, block a protein that promotes the growth of these abnormal vessels, helping to reduce leakage and preserve vision.
While anti-VEGF injections are the primary approach, other interventions may be considered. Laser photocoagulation, using a focused laser to seal leaky vessels, has largely been replaced by anti-VEGF therapy due to better outcomes. Photodynamic therapy (PDT) with verteporfin, an older treatment, uses a light-activated drug to close abnormal vessels, with limited long-term effectiveness compared to anti-VEGF agents. For issues like retinal detachment, surgical options such as pars plana vitrectomy or macular buckling may be necessary to reattach the retina.
Beyond medical interventions, managing daily life with myopic degeneration can involve using low-vision aids like magnifiers or specialized software. Protecting the eyes from harmful UV light with sunglasses that block 99-100% of UVA and UVB rays is also recommended to prevent further damage.