The visual acuity of people with low vision varies widely, but, in general, low vision is defined as a condition in which a person's vision cannot be fully corrected by glasses, thus interfering with daily activities such as reading and driving. Low vision is more common among the elderly, but it can occur in individuals of any age as a result of such conditions as macular degeneration,glaucoma, diabetic retinopathy, or cataracts.

Cataract
A cataract is a clouding of the lens of the eye. The lens is a clear oval structure with three layers: the nucleus, the cortex, and the capsule. It may help to think of the lens structure as a peach, where the nucleus is the peach pit, the cortex is the flesh of the peach surrounding the pit, and the capsule is the peach skin, or elastic covering of the lens. You have a cataract when the nucleus becomes opaque (that is, it is no longer clear) or when small opacities develop in the cortex that block or scatter light.

Diabetic Retinopathy
Diabetic retinopathy is a potentially blinding complication of diabetes that damages the eye's retina.
Diabetic retinopathy occurs when diabetes damages the tiny blood vessels in the retina. At this point, most people do not notice any changes in their vision.
Some people with diabetic retinopathy develop a condition called macular edema. It occurs when the damaged blood vessels leak fluid and lipids onto the macula, the part of the retina that lets us see detail. The fluid makes the macula swell, blurring vision.

As the disease progresses, it enters its advanced, or proliferative, stage. Fragile, new blood vessels grow along the retina and in the clear, gel-like vitreous that fills the inside of the eye. Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina.

Glaucoma
Glaucoma is the term for a diverse group of eye diseases, all of which involve progressive damage to the optic nerve. Glaucoma is usually, but not always, accompanied by high intraocular (internal) fluid pressure. Optic nerve damage produces certain characteristic visual field defects in the individual's peripheral (side), as well as central, vision. There are three basic types: primary, secondary and congenital.

Macular Degeneration
As the most common cause of vision loss among people over the age of 60, macular degeneration, often referred to as age-related macular degeneration (AMD), impacts millions of older adults every year. The disease damages the macula, the central part of the retina, and can sometimes make it difficult to read, drive or perform other activities requiring fine, detailed vision. The damaged parts of the macula often cause scotomas, or localized areas of vision loss. When you look at things with the damaged area, objects may seem to fade or disappear. Straight lines or edges may appear wavy.

Signs of low vision include:

• Difficulty recognizing a familiar face
• Difficulty reading - print appears broken or distorted
• Difficulty seeing objects and potential obstacles such as steps, curbs, walls and furniture

Low vision services do not cure the cause of low vision but rather utilize the remaining vision to its fullest potential.

The Objectives Of Low Vision Assessment is to:

• Achieve a reasonable understanding of several aspects of ocular condition and its management.
• Comprehend the psychosocial considerations of a patient in employment faced with visual loss and loss of independence.
• Understand the necessary components of a low vision assessment and their significance.
• Understand the use of environmental modifications, the principles underlying the selection of specific low vision aids, and the use of adaptive computing solutions.
• Appreciate the role of state agencies for blindness rehabilitation and understand the fiscal environment for rehabilitation. Grasp the concepts underlying the multidisciplinary approach to comprehensive low vision, vocational rehabilitation, eye condition education for the visually impaired.

Low vision testing goes far beyond regular eye examinations. A careful assessment is made of the patient's vision, while exploring the effect of increasing the size of the image on the retina. Close attention is also given to the effects of decreased vision on the patient's lifestyle, and a plan is designed to meet the patient's needs and goals. A typical low vision examination takes about two hours .

The exam usually consists of:
      1. A look at the patient's history, which can cover hobbies, daily life, educational background, current health, and goals for the future.
      2. Testing of vision to make certain that current prescriptions are correct, in addition to an analysis of the patient's ability to see eccentrically, or "off-centre." This is particularly useful for macular degeneration patients who have lost the use of their central vision.
      3. Introduction of low vision aids for both near and distance viewing, and determination as to which devices will work best for the patient. These devices include magnifiers, closed circuit television systems (CCTVs), and independent living aids. The patient learns how to use these aids, while developing skills to maximize remaining vision.
      4. Discussion of recommended adaptations to the patient's home and work environment.
      5. Discussion of types of lenses which can help to cut brightness, glare, and ultraviolet rays.
      6. Scheduling of a home visit to help set up and demonstrate adaptive equipment, analyze lighting, mark appliances, and/or to inspect for safety.

A visit with a low vision specialist can help a visually-impaired person to lead a fully independent life despite visual restrictions. There are also low vision rehabilitation centers which house teams of low vision specialists, rehabilitation teachers, mobility/orientation specialists, occupational therapists, and other professionals in other areas as needed.