Factors affecting the clinical testing of accommodative facility

Abstract

A number of variables in the accommodation flipper test are thought to contaminate the results: the time for naming symbols; the manual facility to actually operate the flippers; the minification or magnification of symbol target size by the lenses; saccadic eye movements; and the relationship between the accommodation stimulus and its response. With the exception of the last variable, all undesirable factors have been eliminated in a newly developed modified method of accommodation facility measurement. In this method, double measurement through plano and +/- 2.00 D lenses, is executed. The average time in seconds per one cycle, taking only the accommodation into account for a group of 43 children (age from 7 years 11 months to 9 years 11 months), is 3.7 monocularly and 8.5 binocularly and the average number of cycles per minute in this group is 32.1 and 33.8 monocularly (for the dominant and nondominant eye, respectively) and 22.6 binocularly. These results in sec/cycle do not differ considerably from results received by other authors, if one considers the time necessary for naming the digits, mechanically changing the lenses, saccadic eye movements etc., and even those results given in cycles/minute do not differ either taking the wide ranges of standard deviations into account. However, the method reported here reflects accommodation facility more precisely. Measurements were performed also with the hand held flipper. Comparison of results summarised above and those obtained with a hand held flipper demonstrates that the hand held flipper is not a good device to measure accommodative facility.