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A clinical protocol for the determination of monocular alignment hyperacuity

1 April 1995


Hyperacuity describes a variety of visual functions which are measured at thresholds smaller than expected given comparatively large receptor spacing and the subsequent predicted retinal image quality of the human eye. Monocular alignment hyperacuity is the ability to make very fine judgments of lateral or vertical displacement. There are numerous clinical uses for monocular alignment hyperacuity; however, there exists little procedural continuity among research in this area. This lack of continuity makes clinical adaptation and interpretation difficult. This project attempts to establish an efficient protocol for the measurement of monocular alignment hyperacuity in order to increase its clinical applicability and interpretability. Nineteen subjects each performed 300 trials at two testing distances using the method of subjective adjustment to alignment. The distribution of errors from alignment allow calculation of monocular alignment hyperacuity. Results indicate that a useful and consistent monocular alignment hyperacuity can be obtained in 250 trials on any cooperative subject or patient. Methods are suggested to decrease the number of trials necessary for clinical efficiency. Additionally, even though the angular subtense of the test stimuli were kept constant at one meter and six meters, the six meters testing distance yields lower thresholds (greater sensitivity) than that of the one meter distance, possibly due to increased peripheral cues to alignment.


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