Purpose: Recent studies have investigated Eyetronix Flicker Glasses (EFG) in treating refractive amblyopia. EFG provides rapid alternating occlusion of the two eyes at a particular rate. They have been shown to cause a significant improvement in visual acuity, contrast sensitivity, and stereoacuity in amblyopes. Amblyopia is a syndrome marked by a reduction in visual acuity as well as other monocular functions like fixations, saccadic eye movements, and accommodative lag. The purpose of this study was to investigate the intra-treatment effect of 7 and 20 Hz flicker on fixations, saccades, and the accommodative lag during reading, and on stereoacuity.
Methods: A Latin Square was used to balance the treatment order within subjects and order sets were randomized across subjects. 51 normal subjects (ages 22-34) were enrolled in the study. Fixations and saccades during reading were tested with infrared oculography (ReadAlyzer, Compevo AB, Stockholm, Sweden). The Grand Seiko WAM-5500 open-field autorefractor was used to measure accommodative lag. Distance Lea Stereo (M&S chart) was used to determine the stereoacuity. Each test was performed three times (no flicker glasses, 7 Hz flicker glasses, and 20 Hz flicker glasses). Outcome measures were: (1) number of fixations, (2) number of regressions, (3) fixation duration, (4) reading rate, (5) accommodative response, and (6) stereoacuity.
Results: Among the experimental conditions (no EFG, 7 Hz EFG, and 20 Hz EFG), the number of fixations, regressions, fixation duration, and accommodative lag did not differ significantly (p= 0.98, 0.33, 0.12, and 0.084, respectively). Reading rate (p < 0.05) and stereoacuity (p < 0.001) showed a significant difference, with 7 and 20 Hz negatively impacting reading rate and stereopsis. Reading rate dropped 18 words per minute with 7 Hz (7.4%), and 13 words per minute with 20 Hz (5.4%) compared with no flicker glasses. Stereoacuity was worse by 73 arc seconds with 7 Hz, and 17 arc seconds with 20 Hz.
Conclusion: While using EFG, most visual skills explored by this study are unaffected. However, while worn, the goggles at 7 Hz and 20 Hz reduced reading rate as well as stereopsis.
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