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Apoorva Karsolia, Lawrence R Stark; Patterns of accommodation in lens-simulated anisometropia. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
Accommodation in anisometropia may respond consensually and produce a yoked accommodative response, or respond independently leading to asymmetrical accommodation responses (anisoaccommodation). A prospective, randomized study was conducted to examine the effect of conflicting accommodative stimuli in isometropic individuals (inter-ocular difference ≤ 0.5 D) with ±2 D lens-induced anisometropia and to assess the effects of viewing (binocular or monocular), anisometropia level, test distance and time on the patterns of the accommodative response.
Dynamic accommodation responses were measured in 16 young, visually-normal isometropic subjects with the Grand Seiko WAM 500 Autorefractor. In the 2 sessions, the viewing condition (monocular or binocular; direct or consensual), the testing distance (400 cm, 38.6 cm and 20.5 cm) and anisometropia level (+2 D,-2 D or no anisometropia) were randomized for each subject. In each dynamic trial, accommodation at the 5th ±0.5 second and 20th ±0.5 second was analysed to understand the patterns of the accommodative response. A within-subjects analysis of variance (ANOVA) assessed the factors in the model.
A significant effect of target distance and anisometropia level was found in the group (p < 0.0001). Time as a factor was not statistically significant. Post hoc Tukey analyses showed that 3 hypothesized models of accommodation (least accommodative effort, accommodation towards tonic accommodation, and accommodation driven by ocular dominance) were significantly different from the actual binocular responses (p < 0.0001), and that 3 other models (maximum accommodative effort, weighted average of two eyes, and full anisoaccommodation) were not significantly different from the actual responses. ANOVA demonstrated a more pronounced difference between the hypothesized patterns of accommodation at the near viewing distance.
In the group, three hypothesized models of accommodation were better at predicting the accommodation response in lens-simulated anisometropia. These were the strategies of maximum accommodative effort, weighted average of two eyes, and anisoaccommodation. It is possible that 3 sub-groups of subjects follow each of the 3 strategies separately. Alternatively, individual subjects might switch between the 3 strategies during extended viewing.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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