October's - Tip For Parents
From ISVI's Low Vision Department
 

LOW VISION

What is Low Vision?
Low Vision is a bilateral impairment to vision that significantly impairs the functioning of the patient and cannot be adequately corrected with medical, surgical, therapy, conventional eye wear or contact lenses. It is often a loss of sharpness or acuity but may present as a loss of field of vision, light sensitivity, distorted vision or loss of contrast. Low vision often may occur as a result of birth defects, injury, the aging process or as a complication of disease. The Low Vision Gateway.
Low Vision differs from blindness in that it refers to people who still have useful vision that can be improved with visual devices. Low vision generally means a person's vision does not meet their needs, whether their visual impairment be mild or severe. St Louis Society for the Blind and Visually Impaired.

These terms are often confused due to the “legal” definition for blindness that the federal government developed which is based on visual acuity and field loss and includes persons with low vision.

Definitions of Visual Impairment:
Federal:

• Legal Blindness– A visual acuity of 20/200 or less in the better eye with best correction; or the size of the field of vision is constricted to a diameter of 20 degrees or less.
   

• I.D.E.A. – (educational) a visual impairment that, even with correction, adversely affects a child’s educational performance.

State:

• Educational – The child’s visual impairment is such that the child cannot develop his or her educational potential without special services and materials.
   

Illinois Vision Leadership Council:

• Students with visual disabilities are those who have disorders in both the structure within the ocular pathway AND function of both eyes, that with the best refractive correction and medical/surgical treatment, interfere with learning, as determined by a functional vision assessment. The functional vision assessment is administered by certified teacher for students with visual disabilities. These students would exhibit one or more of the following:

Bilateral reduced visual acuity after best refractive correction, usually 20/70 or less in the better eye, and /or restricted field of vision to the degree that they affect the student’s ability to function educationally;

Progressive and/or permanent eye conditions as noted by an eye specialist on an ocular report;

Eye conditions that result in temporary reduction in vision that affects the student’s ability to function educationally;
 

Medically diagnosed cortical vision impairment.

What is acuity?
Visual acuity is the eye's ability to detect fine details and is the quantitative measure of the eye's ability to see an in-focus image at a certain distance. Acuity is measured as a fraction of normal vision. 20/20 vision indicates an eye that sees at 20 feet what a normal eye should see at 20 feet

What is visual field loss?
Loss of the ability to view through a portion of their viewing field. A visual deficit may be central or peripherally or elsewhere in the visual field. 40-20 degree field or less in the best viewing eye is considered visual impairment.

What causes low vision?
Low Vision can be caused by a multitude of circumstances. Low vision can be caused by birth defects, prematurity, inherited eye condition, injuries, glaucoma, cataracts, or retina or optic nerve conditions. Most often older individuals experience low vision due to macular degeneration, cataracts, or aging.

What are Low Vision Devices?
Optical- The use of lenses or combinations of lenses to provide magnification. The main types of optical devices include: magnifiers: hand, stand and/or lighted; Telescopes, Binoculars, and Monoculars; Closed-Circuit Television and Computer Equipment.
Non-optical- Non-optical devices refers to aids which are not based on lenses and magnification but rather aids which may be enlarged to make their viewing or the activity easier to use. Such devices include: Large print, writing guides, enlarged print for devices such as clocks, telephones, watches, talking devices for watches, clocks, calculators, and reading stands and lighting. Strategies to enhance vision- Position of materials are considered a strategy to access print. Lighting and contrast are used to enhance vision. Eccentric viewing can also enhance a person’s vision. This is a technique to view through a person’s peripheral vision or their the best area of vision, where ever that may be in their visual field.

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