Abstract
The Ocular Photosensitivity Analyzer (OPA), a new automated instrument to quantify the visual photosensitivity thresholds (VPT) in healthy and light sensitive subjects, is described. The OPA generates light stimuli of varying intensities utilizing unequal ascending and descending steps to yield the VPT. The performance of the OPA was evaluated in healthy subjects, as well as light sensitive subjects with achromatopsia or traumatic brain injury (TBI). VPT in healthy, achromatopsia, and TBI subjects were 3.2 ± 0.6 log lux, 0.5 ± 0.5 log lux, and 0.4 ± 0.6 log lux, respectively. Light sensitive subjects manifested significantly lower VPT compared to healthy subjects. Longitudinal analysis revealed that the OPA reliably measured VPT in healthy subjects.
Highlights
Photophobia, first described as an abnormal intolerance to light [1], is a disorder that affects up to 25% of the population
No significant change was noted for the healthy subjects (Fig. 8, p = 0.98), demonstrating the reliability of the Ocular Photosensitivity Analyzer (OPA)
The healthy subject (ID#8) with the lowest visual photosensitivity thresholds (VPT) had a percent change in pupil diameter (24%) similar to the achromatopsia group. These results suggest that lower VPT may be associated with larger baseline pupil diameter, lower percent change in pupil diameter, smaller palpebral fissure height, and higher percent change in palpebral fissure height
Summary
Photophobia, first described as an abnormal intolerance to light [1], is a disorder that affects up to 25% of the population. Since visual photosensitivity is associated with various ophthalmic and neurologic pathologies, quantifying the visual photosensitivity thresholds (VPT) of these individuals may help determine the progression and severity of these disorders. Wirtschafter and Bourassa [27,28,29] investigated the threshold of discomfort to bright light in normal subjects as well as subjects with neurologic and ophthalmic disorders. They positioned the subjects 50 cm from a large translucent screen marked at the center with a 6 cm fixation target. The luminance at which the subject pressed the button was considered to be the VPT for the trial. The variability of the measured VPTs prevented reliable group comparisons
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