Abstract
Purpose: :
Stereopsis is exquisitely sensitive to many of the more subtle disturbances of the vision process, including uncorrected refractive error and sensory/motor fusion problems, making accurate measurements of stereoacuity is critical for both research and clinical purposes. We have developed a novel customizable computer-based random-dot stereoacuity test that overcomes many shortcomings of current clinical stereo testing, such as incomplete dissociation, memorization, and parallax. Our test can be presented on a standard CRT with direct viewing, or minimized on a back-projected screen using a high resolution DLP projector and relay optics. Here we compare the repeatability and reliability of the MVA Computerized RDS test to existing clinical stereo tests.
Methods: :
Pairs of random-dot bitmap images were created in MatLab and displayed at 1600x1200 resolution at 5 meters. Image pairs were alternated at 80Hz and viewed though LCD shutter glasses oscillating in phase at the same frequency, completely dissociating the image pairs without residual monocular cues. Sets of RDS images were generated at 18cpd in approximately 0.125 log second steps from 9.9 - 237.6 seconds, and designed so that multiple sets of targets could be displayed on a single screen, reducing test time. Stereoacuity thresholds of six healthy presbyopic subjects (mean age 48.6yo) with normal binocularity were measured with best correction using our new MVA RDS test and compared to threshold measurements from currently available computerized RDS and stereo ring tests using red/green anaglyphs (Innova ProVideo). Six threshold measurements were taken on each test (3 measurements on two separate days) for each subject.
Results: :
Across all subjects, the MVA RDS test provided lower threshold values (mean=38.5") and lower standard deviation (mean SD=9.13") than the clinical RDS (mean=44.0"; mean SD=21.1", p=0.029) and stereo ring test (mean=68.6"; mean SD=23.0", p=0.039). In terms of mean standard deviations as ratios of mean thresholds, the MVA RDS test provided lower ratios than the clinical RDS (p=0.007) and stereo ring test (p=0.044).
Conclusions: :
The MVA computerized stereoacuity test is a repeatable, valid test that can incorporate a broad range of customized targets and can be scaled for different distances, including optical minimization for near testing.
Keywords: binocular vision/stereopsis • clinical research methodology