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V Rajaram, JA Beatty, V Lakshminarayanan; Repeatability of Longitudinal Horopter Data for Fixation Distances of 40cm and 75cm . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4714.
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Purpose:No study has addressed the effects of repeated trials over several days on the shape and deviation of the longitudinal horopter. This study investigates the repeatability of horopter data for a group of young healthy adults, within 21 to 31 years of age and with normal binocular vision (n=5) over a period of 15 to 30 days Methods:Subjects were asked to align test rods in an Apparent Frontoparallel Plane (AFPP) horopter device. Multiple trials were taken and averaged for each subject at two fixation distances of 40cm and 75cm while wearing correction. To ensure stability of response and to minimize effects of fatigue and learning, the trials were performed at daily intervals. Results:R0 and H values were calculated as described by Ogle (J.O.S.A. Vol 22, 1932, 538-631). Linear regression was performed using each coefficient versus time measured in days. For the coefficient R0, the mean slope found was 3.40E-04 with a standard error of 6.00E-05, and for the H coefficient the mean slope was found to be 2.72E-03 with a standard error of 1.73E-03 for a fixation distance of 40cm. For the 75cm fixation distance the coefficient R0 had a mean slope of 7.70E-03 with a standard error of 4.99E-03, and the mean slope for the H coefficient was 1.79E-03 with a standard error of 1.73E-03. T-tests were performed to compare coefficient values obtained from daily trials. Conclusion:Analysis of the equations indicates that there is no significant change in the R0 and H coefficients over time. Results of T-tests performed showed no significant difference. These results indicate that the AFPP horopter data is reproducible for normal subjects.
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