Myopia, or nearsightedness, affects a large portion of the global population, usually causing blurred distance vision easily corrected with glasses or contact lenses. Degenerative myopia, also called pathological myopia, is a distinct and severe form that goes beyond simple refractive error. This progressive disorder involves structural changes within the eye that can lead to irreversible vision impairment. Degenerative myopia represents one of the world’s leading causes of legal blindness.
Defining Degenerative Myopia
Degenerative myopia is characterized by the excessive, ongoing elongation of the eye’s axial length, causing the eyeball to grow much longer than normal. While high myopia is defined by a refractive error of -6.00 diopters or greater, degenerative myopia is distinguished by pathological changes in the back of the eye, regardless of prescription strength. The continuous stretching physically thins the delicate tissues lining the interior of the eye, particularly the retina, choroid, and sclera.
This elongation causes the eye’s internal coats to become taut and fragile. Thinning of the sclera can result in an irregular protrusion called a posterior staphyloma, which further distorts the shape of the retina. This structural damage, rather than poor focus alone, defines the condition and increases the risk of severe complications and vision loss. These degenerative changes often worsen over time, even into adulthood.
Specific Complications Leading to Vision Loss
The stretching and thinning of the posterior eye tissues result in several pathologies that directly threaten central and peripheral vision. Myopic maculopathy is a collective term for damage to the macula, the central part of the retina responsible for fine detail and color vision. This damage often presents as lacquer cracks, which are tiny ruptures in the Bruch’s membrane, leading to scarring and atrophy.
A particularly severe complication is myopic choroidal neovascularization (mCNV), where abnormal blood vessels grow beneath the retina. These vessels can leak fluid or bleed, causing rapid distortion and loss of central vision. If left untreated, the resulting scar tissue, known as a Fuchs spot, can cause permanent blind spots.
The thinned retina is also prone to tearing and detaching from its underlying support layers, known as retinal detachment. This complication requires immediate surgical attention, as the separation starves the retinal cells of oxygen and nutrients, quickly leading to permanent vision loss. The altered structure of the elongated eye can also increase the risk of developing glaucoma, a disease that damages the optic nerve and causes gradual, irreversible loss of peripheral vision.
Active Management and Treatment Strategies
While there is currently no cure to reverse the excessive axial elongation that defines degenerative myopia, timely management can limit vision loss. Early detection through regular, specialized eye exams is paramount, especially for individuals with high myopia or a family history. Advanced imaging techniques, such as Optical Coherence Tomography (OCT), monitor the structural integrity of the retina and choroid for signs of damage.
The treatment for the most sight-threatening complication, mCNV, involves anti-vascular endothelial growth factor (Anti-VEGF) medications. These drugs are injected directly into the eye to halt the growth of abnormal blood vessels and reduce leakage, often stabilizing or improving vision. If a retinal detachment or a large macular hole occurs, surgical intervention, such as a vitrectomy, is performed to reattach the retina.
In children and adolescents, the focus is on slowing the progression of axial elongation to prevent severe degenerative changes. This is achieved through interventions like low-dose atropine eye drops and specialized contact lenses, which modulate the eye’s growth signals. Encouraging increased time spent outdoors is also recommended for slowing the progression of myopia in younger patients.