Basically, “low vision” describes significant visual impairment that can’t be corrected fully with glasses, contact lenses, medication or eye surgery. It includes
- Loss of best-corrected visual acuity (BVCA) to worse than 20/70 in the better eye.
- Significant visual field loss. Tunnel vision (lack of vision in the periphery) and blind spots are examples of visual field loss.
- Legal blindness. In North America this is 20/200 or less central visual acuity in the better eye with best possible correction, or a visual field of 20 degrees or less.
- Almost total blindness.
- Eye diseases are a common cause of low vision:
- Hazy, blurry vision can result from cataracts.
- Blurred or partially obscured central vision is typical of macular degeneration.
- Diabetic retinopathy causes blind spots, blurriness and visual distortions.
- Poor peripheral vision is a hallmark of glaucoma.
- Retinitis pigmentosa reduces peripheral vision and the ability to see in the dark.
- Light sensitivity and loss of contrast are other symptoms of these and other diseases.
- Heredity and eye injuries also can result in low vision.
Low Vision Aids are tools that help those with vision loss maximize their remaining vision and these devices fall into one of three broad categories:
- Optical devices
- Electronic devices
- Non-optical devices
- Monocular telescope (Hand held and Spectacle mounted)
- Binocular telescope
- SEE TV (Spectacle model telescope)
- Spectacle magnifiers
- Stand magnifiers
- Hand held magnifiers
- Dome magnifiers
- Fresnel book magnifiers
- Pocket magnifiers
- Letter writer
- Signature guide
- Talking watch
- Braille slate and style
- Braille scale & geometry set
- Walking stick
- HKSB filters
- Clip-on filters
- Tinted lenses