Low vision is a condition where the eyesight can’t be corrected with glasses or contacts, but there is still some sight left. It’s not blindness because there are some areas with limited sight. Low vision may include blind spots, poor night vision, and blurry sight. One common cause of low vision is age-related macular degeneration. Visual aids may help with low vision, which is a convenient and affordable way to live with low vision.
What is low vision?
Low vision is a visual impairment that cannot be corrected with prescription eyeglasses, contact lenses, or surgery. A person who has low vision may never go completely blind because they still have some sight and it can sometimes be improved with the use of visual aids.
Low vision and blindness refer to a decrease in the ability to see visual images. There are many different types and degrees. The American Optometric Association (AOA) defines low vision and blindness as two different categories.
- “Partially sighted”: The person has a vision that ranges from 20/70 – 20/200 with regular prescription lenses.
- “Legally blind”: The person has a vision that is worse than 20/200 with regular correction, or a field of view that is less than 20 degrees wide.
The ratio measurement describes the sharpness of vision at 20 feet from an object. For example, if your vision is measured at 20/70, you must be 20 feet away to see what a person with good eyesight can see at 70 feet.
Causes of low vision
There are a number of possible causes of low vision. Most often, these are the result of problems with the eye or a problem that affects the entire body, such as diabetes. Some of the most common causes of vision-impaired individuals are age-related macular degeneration, diabetes, and glaucoma. Vision-impaired individuals may also have cancer of the eye, albinism, or an injury to the brain. Individuals with these disorders or who are at risk for them also have a greater risk of experiencing vision impairment.
Diagnose low vision
A specialized eye exam by your low vision specialist can diagnose low vision. If you experience any difficulties with activities like travel, cooking, working, or going to school, it’s best to make an appointment with your eye doctor as soon as possible. In order to diagnose the severity of the condition, the doctor will perform tests like looking at your vision under different lighting conditions and giving you magnifying lenses and charts to test your visual acuity, depth perception, and visual field.
Macular degeneration
Macular degeneration is a condition that affects the retina, which is the lining of the eye that focuses on images. The macula, which produces central vision, deteriorates causing blurred vision, which can make it difficult to read. For some people, they might experience a blurry spot, while other people might lose their central vision completely.
Age-related macular degeneration, or AMD, is usually broken down into two categories: Wet AMD and Dry AMD. Wet AMD is when abnormal blood vessels form under the macula, which then causes fluid and blood leakage. Dry AMD on the other hand progresses more slowly and gradually because it’s not related to any abnormal growths.
Cataracts
A cataract is a clouding of the eye lens that changes how light is focused on the retina. It interferes with light reaching the retina, which results in a general loss of vision. Causes for cataracts can be aging, UV exposure, injury, or inherited disorders. If the eye is healthy, a cataract can be surgically removed and replaced with a new lens. Usually, this makes the eye better than it was before. But if a person has other eye diseases, they may need low-vision rehabilitation to maximize their remaining vision.
Glaucoma
Glaucoma is caused by damage to the optic nerve from increased pressure from fluid inside the eye. This often occurs due to improper flow or drainage of fluid within the eye, or a lack of blood supply to the optic nerve. There are no early symptoms for most types of glaucoma, but the first signs of damage are defects in peripheral vision and difficulty with night vision. If diagnosed early, it can be treated with either medication or surgery which may help minimize vision loss.
Diabetic retinopathy
Diabetes can cause blood vessels that nourish the retina to develop abnormal branches that leak, called diabetic retinopathy. This can interfere with vision and overtime may severely damage the retina. Laser procedures and surgical treatments can reduce its progression, but the best way to treat it is by regulating your blood sugar levels.
Retinitis pigmentosa
Retinitis pigmentosa is a disease that gradually destroys night vision and significantly reduces side vision. It is a hereditary disease that affects more children than adults — the first symptom, night blindness, usually appears in childhood or adolescence.