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Medical Forum / General / Vision / February 2006presbyopia
Prior to lasik I could see clearly to a distance of 3". Now have blurred vision if an object is closer than 6" to the eye. I understand that the lasik correction for distance vision will reduce the focusing ability up close. Is this much of a change normal? What is "normal" up close vision (distance before blurring) for someone with no correction needed for distance vision? At what age does presbyopia normally begin? Is it gradual over several decades or occur rather quickly? Do exercises that force the eye to focus at close range then distance delay its progression? > Prior to lasik I could see clearly to a distance of 3". Now have blurred > vision if an object is closer than 6" to the eye. I understand that the > lasik correction for distance vision will reduce the focusing ability up > close. Is this much of a change normal? Absolutely. To understand it better, look into the definition of "diopter." A 3-inch "nearpoint" represents approximately 13 diopters. A 6-inch nearpoint converts to approximately 6.5 diopters. So the effect of LASIK was to increase your nearpoint by about 6.5 diopters. Measured in diopters, you'd expect an identical change in your distance refraction. *If* you got perfect results from surgery, we would suspect that your spectacle prescription was about -6.50 before the procedure. Since diopters are defined as 1/distance, the steps are much smaller at 3 inches than at 3 feet. That makes them much harder to measure accurately, so if the -6.50 estimate is off, it could likely be refined by more careful measurements, and by considering your post-LASIK refraction. > What is "normal" up close vision (distance before blurring) for someone > with > no correction needed for distance vision? At what age does presbyopia > normally begin? Is it gradual over several decades It's gradual early on, but it accelerates predictably after 35 such that age can often be calculated from measurements of accommodation. Age 40 is the classic "age of onset" but that only means your nearpoint increases past a nominal reading distance (16" or 18") at age 40. > Do exercises that force the eye to focus at close range then > distance delay its progression? Probably negligible. Some people claim dramatic results, but after 20 years none of them have ever made it into my office. When the measurements depart from expected values, the variability is usually explained by astigmatism, or small pupils. My own astigmatism at age 52 gives me "adequate" vision at 20", though only for vertical lines. Serendipitously, straining to accommodate also shrinks the pupils, improving vision at near without true accommodation. -MT Great reply! I too was thinking you were a high myope in the -6 range. If you can focus this close, you do NOT have presbyopia. I can focus down to 5 inches without glasses with both eyes open(which increases the depth of field vs. one eye) and my pescription is almost -5 spherical equivalent in the worse eye. With full power glasses, even normal reading distance uses all my accomodation and its a real strain and also bad for the eyes so I always take my glasses off to read and I see fine from 11" due to my myopia. Its so much easier to read without glasses. If I lose this myopic ability I would need reading glasses for any prolonged reading. |
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