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EM Kester, B-C Jiang; The Effect Of Interpupillary Distance On Stereoscopic Threshold . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4674.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous studies showed that when interpupillary distance (IPD) was optically manipulated, the AC/A ratio changed respective to the IPD, i.e., an increase in IPD caused an increase in the AC/A (Judge and Miles, 1985; Ramamiritham et al., 2001). The purpose of this study is to determine how IPD change affects stereothreshold. Methods: Eight optometry students with normal binocular vision voluntarily participated in this study. The subjects IPD was changed by means of a head mounted device to half or double, approximately. An optical apparatus was used to measure the subjects natural IPD and the artificial IPD when he/she wore the head mounted device. The stereothreshold was measured using a Howard-Dolman apparatus placed at 3 m from the subject. The subject was instructed to move the two pegs in the apparatus by means of a string until he/she perceived that the two pegs were parallel to each other. In each IPD condition, twenty settings were made. Then, the standard deviation of these settings, the IPD, and viewing distance were used to calculate the subject's threshold. Results: The averages of the IPD in the three conditions were 35.3(+/-)1.6 (SE), 61.9(+/-)1.4, and 137.4(+/-)2.6 mm, respectively. The corresponding stereothresholds for the three IPD conditions were 20.7(+/-)2.8, 17.2(+/-)3.9, and 56.9(+/-)13.5 sec of arc, respectively. ANOVA result shows that the three thresholds are different significantly (F[2,21]=7.02, p=0.0046). Paired t-test shows that there is no difference between the thresholds in 1/2-IPD and IPD conditions (t=1.20, p=0.270), however, the difference between the thresholds in 1/2-IPD and 2-IPD (t=2.85, p=0.0250), and IPD and 2-IPD (t=3.65, p=0.008) are significant. Conclusion: Our results do not support the idea the the stereothreshold remains the same regardless of IPD. The results suggest that the stereothreshold cannot be held constant when the IPD is artificially increased for some subjects.
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