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Tina K. Green, Joseph M. Miller, Howard P. Apple, Erin M. Harvey, Dawn H. Messer, J. Daniel Twelker; Evaluation Of The Grand Seiko WAM And Apple Micro-display For The Study Of Accommodative Response To Near Stimuli. Invest. Ophthalmol. Vis. Sci. 2011;52(14):835.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the feasibility of using the Grand Seiko WAM-5500 binocular open-field autorefractor (GSWAM) to evaluate the accommodative response of children while they read near text.
The GSWAM was modified to include a bridge-of-the-nose rest instead of a chin rest to allow them to speak with minimal head movement. An iPod touch (Apple, Inc, 326 pixels per inch) was used to present three stimulus displays. Each consisted of 5 logMAR lines of five letters and each display used stimuli of a different size (0.1, 0.4, and 0.7 logMAR at 40cm). Twenty-five 6-12th grade students from schools at which the majority of students were members of a Native American Tribe (Tohono O’odham) with a high prevalence of astigmatism viewed each stimulus display through the GSWAM for a 10 second measurement interval, and were asked to read the letters aloud while the GSWAM was in continuous recording mode, recording spherical equivalent (SE) data at a maximum rate of 5 measurements/sec. SE measurements of approximately -2.50 D would indicate that subjects were accommodating to the 40cm target. Data from the middle 8 seconds of each 10 second measurement interval were included. For each interval, mean SE and standard deviation (SD) of SE were calculated.
At least 8 measurements per 8 second measurement interval were obtained for 96%, 92%, and 92% of subjects in the 0.1, 0.4, and 0.7 logMAR conditions. The table below summarizes the grand mean of SE means, the grand mean of SD means, and the mean number of SE measurements. There were no significant effects of stimulus size on SE or number of measurements. Mean SD was greater for the 0.1 logMAR stimuli (p < 0.05).
A rate of at least 1 measurement/sec was achieved for over 90% of subjects. On average, subjects were accommodating to the near target as predicted. Variability (SD) was greater for the smallest stimulus, which may indicate that subjects’ were varying accommodation to try to resolve the small stimuli. This experimental setup is promising for use in evaluation of accommodative patterns over time during visual task performance.
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