Low Vision: What Every Person With Diabetes Should Know
What every person with diabetes should know
Low Vision refers to persons who have sub-normal vision as a consequence of eye disease or injury, as well as to the eye care and rehabilitative specialty that helps those individuals maximize whatever remaining vision potential they may have. The causes of low vision are varied and numerous; the leading causes in the relatively affluent Western World are age-related macular degeneration, followed by glaucoma, followed by diabetic retinopathy.
Unfortunately, many people have suffered eye complications from diabetes, including severe loss of vision. More tragically, many more will probably do so in spite of all we know about prevention and effective treatment. With the aging of our population, the prevalence of serious visual impairment is expected to rise dramatically, and virtually all of us have family members or friends who are or will be affected. Hopefully, far fewer will suffer vision loss and other disability through effective patient education and the efforts of dedicated health care professionals and researchers. Hopefully, cures for diseases like diabetes and the eye complications its causes are just around the bend.
Until that time, though, it is critical that patients with vision loss be aware of what can be done, right now, to help them cope with that loss. For those who haven't experienced vision loss from diabetes (or any cause for that matter), some familiarity with available treatments might best be viewed as an "insurance policy" of sorts; hopefully, this information will never be needed, but it's nice to have "just in case."The clinical practice of low vision is based upon the twin strategies of magnification and contrast enhancement, but also depends upon cognitive and behavioral integration with the activities of daily living. Magnification can be achieved three different ways:
1. Relative distance magnification entails moving the patient closer to objects of visual interest (for example, by moving closer to a street sign, or holding reading material closer to the eyes with the assistance of lenses having the appropriate power for a closer "working distance").
2. Optical magnification works by using telescopes (for distance viewing), magnifying lenses, microscopes or video magnifiers (for near vision activities like reading or drawing insulin into a syringe) to achieve magnification without moving physically closer to objects.
3. Physical magnification depends upon enlarging materials for use (e.g. large print books, numbers on a telephone touch pad or clock).
A combination of magnification strategies is often employed to achieve the necessary amount of total magnification. An example may be useful.
A patient with 20/400 best corrected vision due to diabetic retinopathy (the big E on the eye chart, with glasses) requires 10x (ten times) magnification to achieve a functional 20/40 level of visual acuity, for example, to see a road sign (400 divided by 40 equals 10). To accomplish this, she can: stand 10 times closer to the sign than somebody with 20/40 acuity (relative distance magnification); use a low vision telescope with 10x magnification (optical magnification); or stand twice as close to the sign in tandem with using a 5x telescope (2x relative distance magnification times 5x optical magnification equals 10x total magnification).
Alternatively, she could convince the Department of Transportation to make the print on road signs ten times larger (physical magnification), though her chances for success are probably poor! From a practical standpoint, patients typically respond best to low vision magnification techniques when best corrected vision is 20/800 or better, since higher degrees of magnification increasingly diminish the user's field of vision (to literally see what I mean, try walking around the room while looking through a pair of binoculars, trying not to bump into everyday objects that are no longer in your field of vision).
Contrast enhancement improves vision independently of magnification by making objects "stand out" more. Much of our visual world has poor contrast (e.g. gray colored cars on gray pavement on a cloudy day), and persons with low vision typically have tremendous deficits in contrast sensitivity (see Figure 1 for an example of low and high contrast objects). Contrast can be enhanced by improved lighting (especially closer, incandescent lighting), improved print quality, employing stark color differences between commonly used items and their surrounding/background environment, and colored filters.
Losing vision to diabetes or any cause is scary stuff – believe me, I know from personal and professional experience. Low vision specialists are devoted to helping patients cope with such loss. Unfortunately, low vision services do not make a visually impaired person's vision "like it used to be." With dedication and professional help, however, they do make the most of what a visually impaired person's vision is now.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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