Myopia, commonly known as nearsightedness, is a prevalent vision condition where distant objects appear blurry while close-up objects remain clear. This occurs because the eye focuses light in front of the retina, rather than directly on it, often due to an elongated eyeball or a steeply curved cornea. Corrective lenses like glasses or contact lenses can typically address this refractive error, providing clear vision. However, myopia exists on a spectrum, with some forms presenting greater challenges and risks to eye health.
Defining High Myopia
Eye care professionals measure the focusing power of the eye, and the degree of myopia, in units called diopters (D). High myopia is defined as a refractive error of -6.00 D or more severe. It is also associated with an increased axial length of the eyeball, typically exceeding 26.0 or 26.5 millimeters.
The Nature of Pathological Myopia
Beyond a high diopter measurement, pathological myopia, also known as degenerative myopia, is a distinct and more severe eye condition. This progressive disorder involves excessive elongation of the eyeball, leading to mechanical stretching and thinning of the eye’s delicate internal structures, including the retina, choroid, and sclera. Pathological myopia is considered a disease process rather than solely a refractive error, as it causes degenerative changes within the eye. Unlike stable high myopia, which often stabilizes in early adulthood, pathological myopia can continue to worsen over time, potentially causing significant and irreversible vision impairment. It can begin in early childhood and carries an increased risk with a family history of myopia.
Associated Ocular Complications
The excessive stretching and structural changes linked with high and pathological myopia can lead to several serious eye complications. Retinal detachment occurs when the retina pulls away from the underlying tissue at the back of the eye. The thinned and stretched retina in highly myopic eyes is more prone to tears and holes, and changes in the vitreous gel can also increase this risk. If left untreated, retinal detachment can result in permanent vision loss.
Another significant concern is myopic macular degeneration (MMD), a condition involving degenerative changes to the macula, the central part of the retina responsible for sharp, detailed vision. MMD can manifest as retinal atrophy, where the retinal tissue thins and breaks down, or as lacquer cracks, which are breaks in the layers beneath the retina. A particularly severe form of MMD involves choroidal neovascularization (CNV), where abnormal new blood vessels grow under the macula and can leak blood, further damaging central vision.
Individuals with high myopia also face an elevated risk of developing glaucoma, a condition characterized by damage to the optic nerve. While the exact mechanisms are complex, the elongated shape of the myopic eye may make the optic nerve more susceptible to damage. Additionally, cataracts, which cause clouding of the eye’s natural lens, tend to develop earlier and are more common in people with high myopia.
Managing High and Pathological Myopia
Managing high and pathological myopia involves a multi-faceted approach focused on preserving vision and addressing complications. Regular, comprehensive eye examinations are important for early detection and intervention, helping to minimize vision loss by monitoring for structural changes or complications.
Corrective lenses like glasses and contact lenses improve refractive error. For children, specific interventions like low-dose atropine eye drops, orthokeratology lenses, and specialized contact lenses designed for peripheral defocus can help slow the progression of myopia by reducing the eye’s axial elongation. While the underlying elongation of the eyeball itself cannot be reversed, these strategies aim to manage its progression and prevent severe outcomes.
Treatments for associated complications are tailored to the specific condition. For choroidal neovascularization, anti-VEGF (vascular endothelial growth factor) injections are a primary treatment to inhibit abnormal blood vessel growth. Retinal detachments or macular holes may require surgical interventions like vitrectomy to repair the retinal structure. Cataracts can be treated with surgery, though the procedure may present unique considerations in highly myopic eyes. A proactive approach to care is important for individuals with these severe forms of myopia.