What Is It?
Low vision is a health condition caused by eye disease that reduces visual acuity to 20/70 or below. People with low vision may be affected in one eye or both and cannot correct or improve vision with prescription glasses, contact lenses, or surgery. Low vision refers to a range of sight loss, which includes blind spots, poor night vision, and an almost complete loss of eyesight. Although people with low vision are not completely blind, the American Optometric Association (AOA) has identified two main categories:
- Visually Impaired: anyone with reduced vision, that cannot be corrected with eyeglasses, contact lenses, or prescription lenses
- Legally Blind: any person with a visual acuity of 20/200 or less, that cannot be corrected or experiences 20 degrees or less in their visual field.
To further understand the degree and range of visual impairments, here is the World Health Organization’s method of classifying visual impairments:
Classification of Visual Impairments
|20/30 to 20/60||Mild vision loss or near-normal vision|
|20/70 to 20/160||Moderate visual impairment|
|20/200 or worse||Severe visual impairment|
|20/500 to 20/1000||Profound visual impairment|
|Less than 20/1000||Near-total visual impairment|
This chart does not include the levels of visual impairment due to the loss of peripheral vision.
Visual acuity cannot always predict whether or not a person is having vision problems. For example, someone may have good acuity (20/50) but experience difficulty in function; or, someone with poor acuity (20/200) may not experience any issues performing daily activities.
Causes of Low Vision
Various eye diseases and conditions can lead to visual impairments, and approximately one in three people are affected by a vision-reducing eye disease by the age of 65.
Most Common Causes:
- Amblyopia (a.k.a. Lazy Eye)typically occurs to infants and young children, causing the visual system to fail. Loss of eyesight and functionality occurs in just one eye and affects up to 3 out of 100 children
- Cataracts cause the clouding of the lens in part or all of the eye, which results in a gradual loss of vision. The first signs of a cataract forming include cloudy vision and noticeable fuzzy spots. They often develop slowly and can impact one or both eyes. Initially, problems with night driving can be ameliorated with anti-reflective coating on eyeglass lenses. For healthy eyes, cataracts can be surgically removed and vision restored to good health.
- Diabetic Retinopathy: A complication that affects the eyes of people with diabetes. This condition can develop in either type 1 or type 2 diabetes due to damaged blood vessels within the retina. Diabetic retinopathy may cause no early signs or a mild vision impairment. This health disease can cause severe or profound visual impairment and may require surgery in advanced cases.
- Glaucoma: An eye condition caused by increased internal pressure due to problems with the flow or drainage of fluids. This causes damage to the optic nerve. There are no early symptoms that indicate the onset of glaucoma aside from defects in peripheral vision and difficulty with night vision. Identifying glaucoma early on allows for treatment by drugs or surgery to minimize loss of vision. If left untreated, it leads to profound to near-total vision loss.
- Macular Degeneration, also known as age-related macular degeneration (AMD or ARMD): A disorder causing blurred or no vision in the middle of the eye. There are no early symptoms of macular degeneration except for a noticeable blind spot that forms. We still do not know the cause of this disease; however, age is the primary contributing factor. For some, cigarette smoking and nutrition can also contribute to the development of macular degeneration. In children, a hereditary form of the disease exists, known as Stargardt macular dystrophy, which can lead to a severe loss of sight.
Signs & Symptoms of Low Vision
There are noticeable signs that indicate the development of vision impairment or eye disease. If you or someone you know is experiencing difficulties, even when wearing regular eyeglasses, here are a few questions to consider:
- Do the lights appear dimmer causing you to strain and stress your eyes?
- Are you having difficulties reading street signs or the names of stores?
- Do you struggle to recognize the faces of your friends and relatives?
- Are you performing regular tasks up close, such as reading, knitting, home repairs, or cooking?
A thorough eye examination is recommended to diagnose the causes of low vision, especially if the following symptoms are present:
- Blurred vision
- Poor judgment of depth
- Loss of central vision
- Double vision
- Confusion when performing visual tasks
- Balance problems
Managing & Treating Low Vision
For some eye health diseases, such as glaucoma, the symptoms and onset of visual impairment can be reduced with drugs or surgery. For others like cataracts, an eye care program which emphasizes a good diet is recommended. When treatment is not available, low vision is inevitable. Depending on the severity of the symptoms, various optical and non-optical devices can help improve visual performance. The following are a few popular low vision aids:
- Specialty eyeglasses, eyeglass lenses, and prescription lenses coatings
- Telescopic systems
- Tablets and other electronic devices using large print or bright lighting
- Hand magnifiers
- CCTV reading machines
- Optical print scanners
- Computers equipped with voice command
Having access to the appropriate visual aids can both improve sight and the overall quality of living. Talk to an eye care specialist to learn where to purchase visual aids as well as to create a successful treatment plan for reducing the effects of a visual impairment.