Myopia, commonly known as nearsightedness, is a refractive error where distant objects appear blurry while close objects remain clear. This condition arises when the eye focuses light in front of the retina instead of directly on it, often due to an elongated eyeball or an overly curved cornea. Pathological myopia is a severe and progressive form of this condition, extending beyond a simple refractive error to involve significant structural changes within the eye. It carries a risk of serious vision impairment, making its understanding and management important.
Understanding Pathological Myopia
Pathological myopia, also referred to as degenerative myopia, is characterized by an excessive elongation of the eyeball, known as axial length. This extreme growth causes the delicate tissues at the back of the eye, specifically the retina, choroid, and sclera, to stretch and thin. These structural alterations define the “pathological” aspect, distinguishing it from common or high myopia, which primarily involves nearsightedness without these degenerative changes. The condition manifests during childhood or adolescence and can progress throughout adulthood, leading to further thinning of ocular tissues.
Identifying the Signs and Causes
Individuals with pathological myopia experience severe and progressively worsening nearsightedness, requiring frequent changes in their corrective lens prescriptions. Beyond blurry distance vision, they may notice other visual disturbances such as distorted vision, where straight lines appear wavy or bent. Blind spots or flashes of light, especially in their peripheral vision, can also occur. An increase in the number or size of floaters, which are small specks or strands that drift across the field of vision, is another common symptom.
The development of pathological myopia is attributed to genetic predisposition, indicating a strong inherited component. Research suggests specific genes play a role in regulating eye growth and tissue elasticity, and variations in these genes can increase susceptibility. While environmental factors might influence the rate of progression, the primary underlying cause remains genetic.
Potential Ocular Complications
The stretching and thinning of ocular tissues in pathological myopia increase the risk of several eye complications. Myopic macular degeneration (MMD) is a concern, often involving choroidal neovascularization (CNV), where abnormal blood vessels grow beneath the macula, leaking fluid and blood and causing rapid vision loss. Another manifestation of MMD is myopic foveoschisis, a splitting of the retinal layers at the macula that can lead to distorted vision and central blind spots.
The elongated shape of the eye also elevates the risk of retinal detachment, where the retina pulls away from its underlying support tissue. This separation can occur spontaneously due to weakened retinal tissue or after minor trauma. Individuals with pathological myopia also face an increased likelihood of developing glaucoma, a group of conditions that damage the optic nerve, often due to elevated pressure within the eye.
Early-onset cataracts, characterized by clouding of the eye’s natural lens, are more common, impairing vision. Peripheral retinal degenerations, such as lattice degeneration, which are areas of thinning in the peripheral retina, also contribute to the increased risk of retinal tears and detachments.
Diagnosis and Treatment Approaches
Diagnosing pathological myopia involves a comprehensive eye examination to assess the condition. This includes a visual acuity test to measure refractive error, followed by a refraction to determine the lens prescription. A fundoscopy is performed to examine the retina and optic nerve for degenerative changes or thinning. Advanced imaging techniques, such as Optical Coherence Tomography (OCT), are used to detect macular changes, including myopic foveoschisis and choroidal neovascularization. B-scan ultrasonography is also employed to measure the eye’s axial length.
Managing pathological myopia focuses on correcting nearsightedness and treating associated complications. Corrective lenses, such as glasses or contact lenses, improve visual clarity for distance. For myopic choroidal neovascularization, anti-VEGF injections directly into the eye, using specific medications, are a common treatment to inhibit abnormal blood vessel growth and reduce leakage.
Surgical intervention, specifically vitrectomy, may be necessary to address retinal detachment or myopic foveoschisis by reattaching the retina or relieving traction on the macula. Glaucoma management involves prescription eye drops to lower intraocular pressure, with surgical options considered if medications are insufficient. Cataract surgery is performed to remove the clouded lens and restore vision. Research continues into methods for slowing axial elongation, including low-dose atropine eye drops or orthokeratology lenses.