Low Vision Aids

A person is said to have Low Vision, if he or she has a significant visual handicap in spite of treatment and best correction with standard eyeglasses or contact lenses. Low Vision should not be confused with blindness. People with Low Vision have a significant visual handicap but they also have significant residual vision. The residual vision may be insufficient to meet the patient's routine needs. But a good percentage of these patients have some degree of usable vision, which can be utilized for their day to day work using special aids or devices. If properly motivated, these patients can potentially benefit with the use of special aids or devices called Low Vision Aids. Saraswati Nethralaya has a dedicated Low Vision Aids Service to help such patients.

Although most often experienced by the elderly, people of any age may suffer from low vision. Low vision can result from birth defects, inherited diseases, injuries, diabetes, glaucoma, high myopia and aging.

The commonest cause is Age Related Macular Degeneration (ARMD), a degenerative disease of the retina, the innermost layer of the eye that perceives light and enables us to see. Macular degeneration affects the central vision. Even when advanced, it does not lead to total blindness because the peripheral vision is still preserved, even though the central vision may be totally lost.

Although reduced central vision is the commonest cause of low vision, extensive loss of peripheral vision as in advanced glaucoma, can also produce low vision due to extremely narrow field of vision. Birth defects or inherited disease producing loss of color vision or increased glare sensitivity (diminished ability of the eye to adjust to light, contrast or glare) can also cause low vision.

Reduced central vision produces difficulty in reading, watching television and recognizing faces. Loss of peripheral vision reduces mobility. Increased glare sensitivity causes difficulty in driving. Impaired color vision results in difficulty in distinguishing different colors. Different types of low vision require rehabilitation with different kinds of Low Vision Aids.

A Low Vision Aid (LVA) is a device or an apparatus that improves or enhances the residual vision in patients with low vision. There is no absolute level of vision above which LVAs will be useful, and below which they will not be. Also there is no one device that is suitable for all situations and all patients. Different devices are needed to fulfill the needs of various patients. Various low vision aids may need to be tried out before the most suitable device or devices is determined for a particular patient.

There are broadly two types of Low Vision Aids: Optical and Non-Optical.

Optical low vision aids use lenses, or a combination of lenses, to magnify the size of objects of regard at distance or near. The lowest magnification compatible with the task to be performed should be used by the patient. The main types of optical devices available are:

Magnifying Spectacles  they have stronger, high-powered lenses compared to the usual eye glasses and are designed for close work. Patients using them need to hold the reading material very close to their eyes in order to keep the print in focus. One needs some practice to get used to these spectacles. They have the advantage of leaving both hands free to hold the reading material. The hands are also freed from holding a magnifying lens, an important consideration in old patients with shaky hands.

Hand Magnifiers they are the most commonly used low vision devices. They offer greater flexibility because the patient can control their position in relation to the eye or the object of regard. Also, the reading material can be held at the normal distance. Some of them may have a self contained light source incorporated in them.

Stand Magnifiers have the magnifying lens mounted on a stand that rests on the reading material.

Sheet Magnifiers  these are essentially plastic sheets with concentric ridges on their surface. These are available as small size pocket magnifiers or large size book readers. However they provide only low magnification.

Paperweight Magnifiers  they rest directly on the print material, which they magnify.

Bar Magnifiers are useful for reading books or the telephone directory.

Telescopes  telescopes are aids to magnify distance objects. They may be hand held or mounted on spectacles. However they have the disadvantage of reducing the field of vision.

These include: 
Large print books and magazines
Large playing cards
Large dial telephones
Enlarging photocopiers
Talking machines, talking watches, talking books, talking calculators, talking diaries & talking computers
Closed circuit televisions : these can provide high magnification (up to 40 times) in an undistorted manner. The patient can get as close as he wishes to the monitor, which may be a small or a medium sized screen of a TV or a computer monitor. Contrary to popular belief, sitting close to the screen does not cause eye damage. Adjustable magnification and contrast make it easy to use.

Illumination has an important role in helping patients with low vision. Even for a normal person with advancing age, increased illumination is needed to perform the same task. Lighting should be ample, placed close to the reading material and be properly directed towards it. Illumination devices like high intensity reading lamps with adjustable arms are of good help.

Visors and cap brims block the dazzling effect of overhead light. Glare control filters incorporated in the spectacles can help control glare and improve function in many patients.