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

Purpose. In the current study, we measured threshold duration required to p erform the tasks of letter identification, letter detection, grating orient ation discrimination, and symmetry detection of targets presented as a func tion of retinal eccentricity. Methods. Targets were presented in the nasal visual field on the horizontal meridian at eccentricities ranging from 0 de grees to 22 degrees. Threshold duration was calculated using a modified sta ircase procedure. Results. We found that for the task of letter identificat ion, the rate of duration sensitivity loss was independent of the letter si re. In contrast, for the tasks of letter detection, grating discrimination, and symmetry detection, the rate of loss was greater for smaller targets t han for larger targets. Conclusion. at equivalent target sizes, fetter iden tification always demonstrated the steepest decline in duration sensitivity with increasing eccentricity. This might be the case if the final stages o f the identification process are rate limiting, It was hoped that by quanti fying duration sensitivity of the peripheral retina, more appropriate tempo ral stimuli could be used in rehabilitation programs that train reading usi ng eccentric preferred retina loci in patients with advanced macular diseas e.