Causes of Low Vision
Some of the most common eye disorders that can cause low vision include:
- Age-Related Macular Degeneration (AMD/ARMD): AMD is a leading cause of vision loss among Americans over age 60. It accounts for nearly half of all low vision cases. It is caused when the central part of the retina that provides sharp detail vision – the macula – is damaged and causes a loss of central vision. There are two types of AMD, wet and dry. Wet AMD is caused by the growth of abnormal blood vessels under the macula. Central vision loss can occur rapidly from wet AMD. In dry AMD, light-sensitive cells in the macula slowly degenerate, leading to a gradual loss of central vision.
- Diabetic Retinopathy: According to the National Eye Institute, more than 30 percent of Americans diagnosed with diabetes have some form of diabetic retinopathy. It is a major cause of vision loss and is directly related to high blood sugar, which damages blood vessels. Diabetic retinopathy can damage both the central and peripheral parts of the retina.
- Glaucoma: Glaucoma is the second leading cause of blindness in adults. Glaucoma causes the optic nerve’s fibers to degenerate producing changes to the visual field, and when severe or untreated, it can cause both blurred vision and tunnel vision. Vision changes from glaucoma occur slowly and usually with no warning signs or symptoms early in the disease. For many but not all, an increase in the intra-ocular pressure of the eye (IOP) is the first sign that there may be glaucoma.
- Cataracts: Over 20 million people in the US alone have cataracts, according to Prevent Blindness America. It appears as a clouding of the lens inside the eye, and when significant, it can feel like looking through a fog and causing increased glare from lights at night. Cataract surgery is perhaps the most frequently performed surgery and is close to 100% successful in creating a clear image on the back of the eye (the retina). Often individuals may no longer have low vision after cataract surgery.
- Retinitis Pigmentosa: RP represents a group of inherited eye diseases affecting the peripheral retina resulting in progressive loss of side and night vision. This type of vision impairment often begins in childhood and progresses over time. While walking individuals with tunnel vision may bump into objects in their side vision. Optical devices that minify the image (like hotel room peepholes), sometimes called reversed telescopes, may be of value. When fields of view become very narrow sighted guides, long canes, and guide dogs become very helpful.
- Stargardt’s Disease: Stargardt’s disease, also known as fundus flavimaculatus, is a retinal disorder that affects the macula early in life and hence, is often also called juvenile macular degeneration or early onset macular degeneration. Unlike age-related macular degeneration, there is never a leakage of blood or fluid, though the same area of the retina (the macula) is affected. The macula is the central part of the retina that is responsible for providing sharp detail and color vision. As in age-related macular degeneration or macular dystrophy, Stargardt’s disease does not affect the peripheral retina and, as a result, individuals do not lose all of their vision.
- Albinism: Albinism is a genetic defect that prevents the body from producing melanin, the pigment that gives hair, skin, and the iris of the eye their color. About one in 17,000 people have albinism. The two major forms of albinism are called oculocutaneous albinism (OCA), which causes individuals to have white or pink hair and skin, a very light blue iris, and ocular albinism (OA), which generally affects only the eyes. Individuals with albinism have reduced vision due to an underdevelopment of the macula. They usually also have nystagmus a side-to-side or up-and-down rhythmic movement of the eyes. They may also have high amounts of astigmatism and often a turned eye (strabismus).
There are many additional causes of low vision, including strokes, TBI (traumatic brain injury) and other diseases common among a wider age range such as Stargardts, albinism, ROP (retinopathy of prematurity), among others.