Low vision is a permanent reduction in eyesight that glasses, contact lenses, medication, or surgery cannot fully correct. It is typically defined as visual acuity worse than 20/70 in your better eye, even with the best possible correction, or a visual field narrowed to 20 degrees or less. Unlike total blindness, people with low vision retain some usable sight, and the goal of treatment shifts from restoring vision to maximizing what remains.
Globally, at least 2.2 billion people live with some form of vision impairment. The World Health Organization estimates that in at least 1 billion of those cases, the impairment could have been prevented or still has not been addressed.
How Low Vision Is Classified
The international classification system breaks vision impairment into severity levels based on how well your better eye sees with correction. Mild impairment falls between 20/40 and 20/70. Moderate impairment ranges from 20/70 to 20/200. Severe impairment covers 20/200 to 20/400. Once acuity drops below 20/400, or the visual field shrinks to 10 degrees or less, the classification shifts to blindness categories.
Legal blindness in the United States is defined as 20/200 or worse in the better eye with best correction, or a visual field of 20 degrees or less. Low vision, then, occupies the space between normal corrected sight and legal blindness, roughly the 20/70 to 20/400 range. Many people with low vision can still see colors, shapes, and movement, but they struggle with tasks that require sharp detail: reading standard print, recognizing faces, or driving.
What Causes It
Most low vision in adults stems from a handful of eye diseases, and age is the biggest risk factor for nearly all of them.
- Age-related macular degeneration (AMD) damages the macula, the central part of the retina responsible for sharp, detailed vision. The dry form involves gradual thinning of the macula over time. The wet form is more aggressive: abnormal blood vessels grow beneath the macula and leak blood or fluid. Both types erode central vision while leaving peripheral sight relatively intact.
- Glaucoma works in the opposite direction, slowly destroying peripheral (side) vision first. Because the loss creeps in from the edges, many people don’t notice it until the disease is advanced.
- Diabetic retinopathy results from progressive damage to the tiny blood vessels feeding the retina. Over time, these vessels leak or become blocked, causing blurred or patchy vision that can worsen unpredictably.
- Cataracts cloud the eye’s natural lens. While cataracts are usually treatable with surgery, in parts of the world without access to surgical care they remain a leading cause of low vision.
Less common causes include retinitis pigmentosa, stroke-related brain damage, and amblyopia (a childhood condition where one eye never develops strong connections with the brain). Eye injuries and genetic conditions can also play a role, particularly in younger people.
How It Affects Daily Life
Low vision doesn’t look the same for everyone. The pattern of loss depends entirely on which part of the visual system is affected.
Central vision loss, common with macular degeneration, creates a blind or blurry spot right in the middle of whatever you’re looking at. Reading becomes difficult because letters disappear. Faces look hazy. You might still navigate a room easily because your side vision works fine, but threading a needle or reading a price tag feels impossible.
Peripheral vision loss, typical of glaucoma, narrows your visual field like looking through a tunnel. You can see what’s directly ahead but miss objects, people, or obstacles off to the side. This makes moving through crowded spaces risky and driving dangerous long before central acuity drops.
Some conditions cause a general haze or reduced contrast across the entire visual field, making it hard to distinguish objects from their backgrounds, especially in dim lighting. Others produce scattered blind spots or extreme sensitivity to glare.
How It Is Diagnosed
A standard eye exam checks visual acuity using a letter chart, but a low vision evaluation goes further. These specialized exams assess how well you function with the sight you have, not just what line you can read on a chart.
One key test measures contrast sensitivity: your ability to detect subtle differences between an object and its background. Standard acuity tests use high-contrast black letters on a white chart, but real life is full of low-contrast situations, like seeing a gray curb against a gray sidewalk or reading a faded receipt. Tests like the Pelli-Robson chart use letters that gradually fade from dark to barely visible, revealing functional difficulties that acuity testing alone can miss. Newer smartphone-based contrast tests are also being developed to make this type of screening more accessible.
A low vision exam also maps any blind spots in your visual field and evaluates how you use your remaining vision for specific tasks like reading, cooking, or moving through unfamiliar spaces. The results guide recommendations for aids and rehabilitation.
Optical and Electronic Aids
A range of devices can amplify your remaining vision. The right choice depends on the type of vision loss, how much sight remains, and which tasks matter most to you.
Handheld magnifiers are the simplest option, using a convex lens to enlarge text or small objects. Magnifying spectacles free up both hands by building the magnification into glasses you wear. For distance tasks like reading street signs or watching a presentation, small telescopes that mount on eyeglasses provide 2x to 10x magnification.
Electronic video magnifiers (sometimes called CCTVs) use a camera and screen to enlarge printed material from 3x up to 60x. You place a book or document on a platform, and the magnified image appears on a monitor. Many models also let you adjust brightness, contrast, and color polarity, switching to white text on a black background if that’s easier to read. Portable versions are small enough to carry in a bag.
Smartphones and tablets have become powerful low vision tools on their own. Built-in accessibility features let you enlarge text, increase contrast, and use voice commands. Apps can read printed text aloud using optical character recognition, identify objects through the camera, or magnify whatever you point the phone at. Computers offer similar screen magnification and text-to-speech software.
Non-Optical Strategies
Technology is only part of the picture. Simple changes to your environment can make a surprisingly large difference. Increasing contrast is one of the most effective strategies: a colored tablecloth with white dishes, black contact paper on a desk where you handle white papers, or bold felt-tip markers instead of ballpoint pens for notes and lists. Telephones, thermostats, watches, and remote controls are available with oversized numbers and high-contrast colors. Tactile (textured) labels on appliances, medications, and pantry items help you identify things by touch.
Audio books and electronic books with adjustable text size replace standard print. Watches, timers, and medical devices like blood pressure monitors and glucose meters with spoken output remove the need to read small displays at all.
Rehabilitation Services
Low vision rehabilitation is a structured program designed to help you use your remaining sight as effectively as possible. It typically involves several types of specialists working together.
A low vision therapist or occupational therapist trained in low vision helps you learn to use optical and electronic aids, practice everyday tasks like cooking and managing medications, and reorganize your home for safety and efficiency. A certified orientation and mobility specialist teaches movement skills for getting around safely, both indoors and outdoors. This training covers perceptual skills, physical navigation, and techniques for crossing streets and using public transportation.
Psychosocial support is also a core part of rehabilitation. Adjusting to permanent vision loss often triggers grief, frustration, and anxiety about independence. Counseling and peer support groups help people work through these responses and rebuild confidence. Importantly, rehabilitation doesn’t need to wait until eye treatment is finished. If you’re still receiving ongoing medical care for an eye condition, rehab services can begin at the same time.