Abstract
Purpose: :
To identify factors that differentiate stereoscopic from non-stereoscopic vision with a small binocular disparity among adults with apparently normal visual functions.
Methods: :
We studied 395 Japanese males (age 43.8±7.7, range 20-58) certified healthy according to the Japan Air Self Defense Force (JASDF) aeromedical standard, with apparently normal visual functions including static stereoscopic acuity (40 seconds of arc or better by the Titmus Stereo Test) and dynamic stereoscopic function (within 20 mm of deviation by the three bars test). Subjects were divided to 2 groups by their confidence in depth perception at 40 seconds of arc in the Titmus Stereo Test: those who were able to distinguish the optotypes by their three-dimensional appearances (n=213), and those who were able to distinguish the optotypes, but not confident in the steric differences between the optotypes (n=182). Distant visual acuity (5 m), near visual acuity (30 cm), angle of strabismus, near point of convergence, and dynamic stereoscopic function were analyzed.
Results: :
No statistically significant differences between the two groups were found in distant and near visual acuity, angle of vertical strabismus, and dynamic stereoscopic function. However, significant differences were observed in age (42.4±8.4 versus 45.45±6.4 years, p<0.05 by Wilcoxon rank sum test), and in near point of convergence (71.5±12.0 versus 74.7±10.3 mm, p<0.05 by Wilcoxon rank sum test). Multivariate analysis suggests that the factors that differentiate static stereoscopic vision from non-stereoscopic visual perception are age (>46, range odds rate 2.20), angle of horizontal strabismus (>2.1 prisms, range odds rate 1.69), and deviation in three bars test (>10 mm, range odds rate 1.62) (p<0.05 by Wald test).
Conclusions: :
Some subjects who cannot perceive static stereoscopic optotypes three-dimensionally are still able to distinguish between different optotypes.In adults with apparently normal visual functions, perception of depth in static stereoscopic vision may be affected by age, angle of horizontal strabismus and dynamic stereoscopic function.
Keywords: binocular vision/stereopsis