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A Review of Low Vision Rehabilitation
Mark E. Wilkinson, OD
Contents
- Introduction
- What is Low Vision Rehabilitation?
- Definitions
- Codes for Low Vision Rehabilitation Diagnoses and Procedures
- Other Vision Impairment Classification Systems
- Epidemiology of Visual Impairment
- Rehabilitation Approach to Low Vision
- The Low Vision Rehabilitation Examination
- Comprehensive Case History
- Determination of the Patient's Vision Enhancement Needs
- The Examination Sequence
- Determination of Refractive Errors
- Visual Function Tests
- Health Assessment
- Applicability of Selected Low Vision Devices
- Magnification
- Vision Rehabilitation Devices
- Rehabilitation Instruction
- Report Writing
- Low Vision Practice Management Considerations
- Conclusion
- References
- Appendix: Computer Software Available for Low Vision Patients
Introduction
Blindness and vision impairment represent a significant burden, not only to those affected by sight loss, but also to our national economy. It is estimated that $468 billion is spent annually on care and services for the blind and visually impaired in the US. (Source: Testimony, National Alliance for Eye and Vision Research before the Labor, Health and Human Services, Education and related Agency Sub-Committee of the House of Representatives Appropriation Committee, March 2005)
Based on this testimony, it should be clear that helping individuals who are visually impaired to function at their highest potential will allow many to remain independent, which will directly impact the personal and economic/social burden vision loss causes.
What is Low Vision Rehabilitation?
Low vision rehabilitation is the management of individuals who have a congenital or acquired impairment of visual acuity, visual field, and/or other functional vision factors. This loss of vision can interfere with the process of learning, vocational or avocational pursuits, social interaction, and activities of daily living. Most importantly, the impairment of vision cannot be adequately improved by conventional refractive measures.
Low vision rehabilitation involves a continuum of care, which begins with medical and surgical intervention and proceeds through to the prescription of low vision devices and vision rehabilitation services.
Vision rehabilitation maximizes the use of residual vision and provides the individual with practical adaptations for their normal activities of daily living and any other desired tasks. As the result of vision rehabilitation, the individual will attain the maximum function of their remaining vision, a sense of wellbeing, and a personally satisfying level of independence.
Maximum functioning is achieved through the use of optical, non-optical, and/or video magnification devices, or by teaching compensatory non-visual techniques. Vision rehabilitation may be necessitated by any condition, disease or injury that causes a visual impairment serious enough to result in functional limitations or disability.
There is no required amount of visual acuity or visual field loss necessary before an individual can be referred for low vision rehabilitation, however, the process of vision rehabilitation is felt to be more effective if it is started as soon as functional visual difficulties are identified and any medical conditions are cured or stabilized. This will allow the low vision rehabilitation team an opportunity to minimize the resultant visual disability and subsequent visual handicap.
Definitions
Before we get started on our discussion of how to care for individuals who are visually impaired, it is important to be sure we are talking the same language. Here are a few definitions:
- Visual Function assesses how the eye and visual system function as determined by visual acuity and visual field measurements.
- Functional Vision refers to how the person functions. Functional vision takes into account factors such as loss of contrast sensitivity, photophobia, and/or ocular motor problems. (Source: American Medical Association’s Guidelines Evaluation of Permanent Impairment, 5th Edition, 2001)
- Low Vision is a visual impairment not correctable by standard glasses, contact lenses, medicine, or surgery that interferes with a person’s ability to perform every day activities. (www.nei.nih.gov/nehep/nehepov.htm)
Traditional Classifications/Definitions of Vision Loss include the following:
- Partially Sighted - Best corrected visual acuity between 20/70 (6/21) and 20/200 (6/60)
- Legal Blindness (World Health Organization): Visual acuity poorer than 20/400 (6/120) and/or a field of vision of 10 degrees or less.
- Legal Blindness (United States): This definition was developed by the Social Security Administration as part of the Social Security Act of 1935: “Remaining vision in the better eye after best correction is 20/200 (6/60) or less OR contraction of the peripheral visual fields in the better eye (A) to 10 degrees or less from the point of fixation; or (B) so the widest diameter subtends an angle no greater than 20 degrees.” The definition further specifies “only remaining visual acuity for distance of the better eye with best correction based on the Snellen test chart measurement may be used.” For visual field determination, Goldmann III4e (for phakic eye) or arc perimeter equivalent is required. (www.ssa.gov/disability/professionals/bluebook/2.00-SpecialSensesandSpeech-adult.htm)
An individual cannot be legally blind in one eye, and/or legally blind without the use of their glasses or contact lenses. Misuse of this definition is the cause of much public confusion about vision loss.
Based on this information, the status of legal blindness using the US definition is much easier to attain (along with its resultant benefits), than is the status of legal blindness using the WHO definition.
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