Types of Low Vision
Vision loss can be caused by eye diseases, as well as eye injuries or traumas. Learn about common eye diseases that can lead to low vision or blindness.
The scene appears clearly focused and unobstructed. The horizontal field of vision with both eyes is 180 degrees.
Reduced Contrast and Glare
Albinism is a lack of normal pigmentation. It can affect eyes with or without affecting skin and hair. People with albinism usually have nystagmus (a shaking movement of their eyes), reduced ability to see small details and difficulty in bright light conditions.
Corneal Dystrophies & Degeneration
Corneal disease or injury results in a cloudiness of the normally clear front surface of the eye. Some corneal diseases are genetically inherited, and others are caused by infections. Some corneal scars are caused by injuries. Cloudiness or scarring of the cornea results in glare and loss of the ability to see small details. Contact lenses may be helpful for patients dealing with corneal disease or injury.
Cataracts are a clouding of the natural lenses inside the eyes. They are most often a result of the aging process, but can occur early in life or even be present at birth. Cataracts result in a cloudiness of vision and problems with glare. They typically do not result in low vision by themselves as they can usually be removed surgically. However, cataracts can accompany other conditions resulting in low vision.
Peripheral Visual Field Loss
Glaucoma is a disease of the optic nerve. The optic nerve is the start of the connective pathway between the eye and the brain. High pressure inside the eye is the biggest risk factor, although a small percentage of individuals develop glaucoma with pressures that are usually considered normal. In its early stages, glaucoma results in a loss of contrast sensitivity, so objects of low contrast may appear washed out. Later, in its advanced stages, glaucoma results in a reduction of peripheral (side) vision and may lead to a reduction in ability to see small details.
Retinitis pigmentosa is a genetically inherited eye disease. Its onset can occur during childhood or adulthood. Its first symptom is usually night blindness. Later, peripheral (side) vision is lost. Inability to see small details can occur in advanced stages of the disease. It is a slowly progressive disease that can lead to total blindness in some individuals.
Hemianopsia is a loss of one half of the field of vision, most often occurring in both eyes. Some common causes are stroke, head trauma and brain tumor. It most often results in an inability to see objects to one side and can cause individuals to bump into objects in their missing field of vision.
Central Visual Field Loss
Macular degeneration most commonly affects individuals over 50 years of age and is the leading cause of vision loss for Americans 65 years of age and older. This eye disease progressively destroys the macula, which is the central portion of the retina — the inside back layer of the eye that records the images we see and sends them via the optic nerve from the eye to the brain. As the macula deteriorates, it becomes more difficult to see straight ahead clearly, though peripheral vision remains intact. Although macular degeneration rarely causes total blindness, loss of central vision can make it difficult to read, drive a car and see objects in fine detail.
Stargardt Macular Dystrophy
Stargardt macular dystrophy is a genetically inherited eye disease that involves the macula, the central part of the retina at the back of the eye. Its onset is usually in individuals less than 20 years old. It results in difficulty seeing small details, and individuals with this eye disease may or may not be aware of a blind spot in the center of their vision. Vision loss usually progresses to a certain point, then remains relatively constant. This disease is sometimes called juvenile macular degeneration.
Diabetic Retinopathy is caused by damage to small blood vessels in the eyes as a result of diabetes. It can affect vision in many ways. Diabetic macular edema, or swelling of the central part of the retina, can cause difficulty seeing small details or distortion of vision. Proliferative diabetic retinopathy, or abnormal blood vessel growth in the eye, can result in severe vision loss due to bleeding into the eye, or a detachment of the retina.