Duration thresholds for target detection and identification in the peripheral visual field.

PURPOSE: In the current study, we measured threshold duration required to perform the tasks of letter identification, letter detection, grating orientation discrimination, and symmetry detection of targets presented as a function of retinal eccentricity. METHODS: Targets were presented in the nasal visual field on the horizontal meridian at eccentricities ranging from 0 degree to 22 degrees. Threshold duration was calculated using a modified staircase procedure. RESULTS: We found that for the task of letter identification, the rate of duration sensitivity loss was independent of the letter size. In contrast, for the tasks of letter detection, grating discrimination, and symmetry detection, the rate of loss was greater for smaller targets than for larger targets. CONCLUSION: At equivalent target sizes, letter identification always demonstrated the steepest decline in duration sensitivity with increasing eccentricity. This might be the case if the final stages of the identification process are rate limiting. It was hoped that by quantifying duration sensitivity of the peripheral retina, more appropriate temporal stimuli could be used in rehabilitation programs that train reading using eccentric preferred retina loci in patients with advanced macular disease.