PURPOSE: This study was designed to investigate the reported decline in the CAlC ratio with aging, as well as the effects of near addition lenses on the CAlC as presbyopia progresses, using a clinical methodology.
METHOD: A cross-sectional evaluation of 93 subjects age 25 to 54 was conducted. Accommodative amplitudes and CAlC ratios were determined for each subject. CA/C ratios were determined using the CAnon R-1 infrared optometer and DOG target with prism placed before the non-measured eye.
RESULTS: The expected age-related decline in the CA/C was seen, beginning at approximately age 32 for subjects as a whole, and at approximately age 27 for those who wore nearpoint lenses. The age-related decline was more predictable for thoe who wore near addition lenses.There was a slight tendency toward higher CAlC ratios among subjects who did not wear near addition lenses. When the CA/C was analyzed by accommodative amplitude instead of age, significant differences (p < 0.05) were found, showing higher CA/C ratios for subjects who did not wear adds.
CONCLUSION: This study presents further evidence of an age-related decline in the CA/C ratio. The rate of decline in the CAlC ratio may be related to the use of near addition lenses.
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