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T Candy, J Wang, GM Tondel; Stability of Accommodative Performance during Infant Acuity/CS Assessment . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2865.
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Purpose: Accommodation has not been measured previously during acuity evaluation in infants. This study assessed whether accommodation remains stable as target spatial frequency increases, or contrast decreases, during VEP acuity recordings. Specifically, the influence of accommodative performance on responses to near threshold stimuli was investigated. Methods: The camera of an eccentric videorefractor (PowerRefractor - Multichannel Systems) and a VEP stimulus were optically superimposed using a 24 inch diameter beamsplitter at a 1 m viewing distance. Measures of accommodative performance were taken at 25Hz while steady-state sweep VEP trials, lasting 10 seconds each, were recorded in infants (over 3 months of age) and adults. Conventionally, a small fixation toy is used to attract infants' attention and provide an accommodative cue during recordings. In this study, accommodative performance was recorded both with and without the toy, to determine the toy's effect on accommodative performance, and on response thresholds as a result of potential foveal occlusion of the stimulus. Results: The acuity and contrast sensitivity estimates, from the responses averaged over a number of trials, were all within the normal range for the infants' ages. Adult mean accommodative response varied little during each 10 second trial, with a standard deviation of less than 0.5D, both with and without the toy. Infants mean accommodative response with the toy varied randomly by approximately 1D during each trial, with a standard deviation of approximately 0.5D. Infants mean accommodative responses without the toy typically drifted systematically about 1D to a more hyperopic position at the end of the trial. The presence or absence of the toy made less than an octave difference in both acuity and contrast sensitivity thresholds in infants and adults. Conclusion: Accommodative performance in infants over 3 months varies little during a VEP acuity assessment. The mean response typically drifts by less than 1D as the stimulus approaches threshold.
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