Low Vision
What is the definition of Low Vision?
Low vision is the loss of sight that is not correctible with prescription eyeglasses, contact lenses or surgery. This type of vision loss does not include complete blindness, because there is still some sight and it can sometimes be improved with the use of visual aids.
Low vision includes different degrees of sight loss, from blind spots, poor night vision and problems with glare to an almost complete loss of sight. The World Health Organisation defines low vision as two categories:
- “Partially sighted”: the person has visual acuity between 20/70 and 20/200 with conventional prescription lenses.
- “Legally blind”: the person has visual acuity no better than 20/200 with conventional correction and/or a restricted field of vision less than 20 degrees wide.
The ratio measurement of vision describes visual acuity, or the sharpness of vision, at 20 feet from an object. For example, having 20/70 vision means that you must be at 20 feet to see what a person with normal vision can see at 70 feet.
How is low vision diagnosed?
An eye examination by your eye care specialist can diagnose low vision. You should make an appointment with your eye doctor if your vision difficulties are preventing you from daily activities like travel, cooking, work and school. The tests the eye doctor will perform include the use of lighting, magnifiers and special charts to help test visual acuity, depth perception and visual field.
Can low vision be Treated?
Some sight disorders, like diabetic retinopathy, can be treated to restore or maintain vision. When this is not possible, low vision is permanent. However, many people with low vision find visual aids helpful. Popular low vision aids include:
• Telescopic glasses.
• Lenses that filter light.
• Magnifying glasses.
• Hand magnifiers.
• Closed-circuit television.
• Reading prisms.
In some patients the restored vision allows for them to independently navigate through doorways, sidewalks, sort light and dark colored laundry, or even read large letters.
Non-optical aids designed for people with low vision are also very helpful. Some popular non-optical devices include:
• Text reading software.
• Check guides.
• High contrast clocks and watches.
• Talking watches and clocks.
• Large print publications.
• Clocks, phones and watches with enlarged numbers.
Visual aids improve both sight and the quality of life for many people. Talk to your doctor about where to purchase visual aids.