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P. K. Ahnelt, C. Glittenberg, D. Meisel, C. Schubert, E. Kostial, B. Viola, S. Binder; Design and Calibration of a Virtual Ground-Level Perimeter for Comparison of the Role of Human and Primate Facial Topographies for Visual Field Limits. Invest. Ophthalmol. Vis. Sci. 2008;49(13):617.
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Maximum borders of human visual field are largely determined by anatomical features. The orthognath human face and bipedal posture allow to extend the view ca. 70° ventrally, allowing visual flow to reach the feet’s immediate foreground but little is known about visual field extension of other primates. We have established a virtual perimetric system to identify variations of anatomical constraints.
Virtual masks were obtained from human subjects and taxidermy specimens of chimpanzee (Pan troglodytes) and baboon (Papio sp.) with a Breuckmann surface scanner and imported to a virtual perimeter developed with Cinema 4D R10.5 (MAXON Comp. Inc.). The masks were positioned at 1,7 m elevation and, centered on the model’s pupils, visual distance/angular scales were demarcated along the virtual floor. Virtual 180° searchlights positioned at the masks’ pupils then allowed to a) "paint" the facial elements obstructing their path (red/green in Fig. a) and b) demarcate the intersection of the unobstructed rays with the perimetric scales on the ground floor. The virtual perimetric settings were adjusted and optimized by comparison with imported actual visual field data from the same human subjects obtained by large stimulus Goldmann perimetry. No attempt to simulate the real optical pathway was undertaken at this stage of the project.
In analog bipedal posture the prognath facial designs of chimpanzees and baboons lead to significant obstructions of the ventral foreground ("anatomical scotomas": >2 m versus 0,5 m in Homo, black zones in Fig. b), while binocular overlaps (yellow) appear significantly enlarged (approx. 125° in chimp versus 90° in human, Fig.b).
The virtual perimeter is able to identify the consequences of specific facial topographies for comparative intra- and interspecific studies on visual field characteristics.
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