The Fine Print
Why am I having trouble reading fine print, and what can be done about it?
One of the most common problems bringing patients in for an eye examination is the loss of ability to focus on small print, such as that commonly encountered when reading a book, a magazine, a newspaper, or a computer screen. This phenomenon is often very frustrating, especially for people who have always had excellent eyesight and rather suddenly discover, typically in their early forties, that they can no longer read fine print without difficulty, extremely good lighting, and/or holding reading material a considerable distance away from their eyes. This age-related loss of near focusing ability, known as presbyopia, affects virtually every person at some point in time, but often occurs earlier than average in people with diabetes (by up to 15 years).
In order to change focus from objects in the distance (for example, a road sign 100 feet away, or even a television set a mere 10 feet away) to objects at near (about three feet or closer), the elastic internal lens of the eye changes its curvature via a series of collagen tethers (ciliary zonules) that attach the lens to an internal focusing muscle (the ciliary muscle); this entire process is known as accommodation. Presbyopia occurs when the elastic fibers within the eye's lens lose their elasticity, something that happens in all human beings over time. For example, it has been shown by a number of very clever experiments that this loss of elasticity and accommodation develops in a rather predictable way starting at around age 10, but typically does not cause symptoms until the majority of our near focusing ability has already been lost, or until the small size of print or materials with which we work up close exceeds our ability accommodate.
Presbyopia is not the result of weak eye muscles; in fact, the ciliary muscle still functions quite well even in octogenarians. Rather, it I due to stiffening of the elastic fibers within the lens itself, resulting in the inability of the lens to change its curvature and a loss of visual clarity up close. Because of this, eye muscle exercises have no benefit for presbyopia (though they do for younger patients with weak focusing muscles). For those of us with diabetes, this process is accelerated by high blood glucose levels that make these elastic fibers both sticky and less flexible, such that trying to change the curvature of the lens becomes like trying to mold a chunk of clay – it can be done, but only with considerable effort.
This is the major reason why people with diabetes often develop presbyopia prematurely, and may end up needing reading glasses or bifocals at an earlier age than their peers. Other than high blood glucose, other environmental factors that accelerate this process include UV light exposure (this sort of ‘cures' the lens) and cigarette smoking (the substances inhaled directly lead to the development of so-called "free radicals" within the bloodstream that are toxic to both lens fibers and the most important part of the eye's light-sensitive retina, the macula, raising the risk of premature presbyopia, cataract and macular degeneration.)
Ultimately, the lens becomes totally inelastic (like a rock) in both people with and without diabetes, and no amount of effort will change its shape. Solutions to this problem are myriad, but none is perfect (they all entail some compromise): bright light will help for a time because it makes the pupil smaller and gives a greater depth of focus; reading glasses that make close objects clear but blur distance objects; bifocals that make both close and far objects clear; trifocals that make close, intermediate and far distances clear; contact lenses that make one eye see better at distance and the other eye better at near (so-called "monovision") or bifocal contact lenses; corneal molding with overnight wear of customized rigid lenses that change the eyes' shape to achieve a monovision effect (sort of like a braces retainer for the eyes); laser surgery to do the same. The only people who ‘escape' the hassles of presbyopia are those who are moderately nearsighted (meaning near objects are clear without glasses, while distant objects are blurry). These folks can simply take off their glasses to read, though their distance vision will suffer.
Presbyopia is a drag - believe me, I know. But at least it can be effectively remedied when the time comes. To minimize its effects and put it off as long as possible, those of us with diabetes should wear ultraviolet eye protection, maintain good blood glucose control, and work assiduously to avoid or quit smoking.
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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