Temporal Aspects of Letter Identification in the Peripheral Visual Field

Many aspects of visual function have been shown to decrease in the peripheral retina. Letter acuity, grating acuity and contrast sensitivity all decrease as a function of retinal eccentricity (Westheimer, 1982). However, increased temporal sensitivity of the peripheral retina has been reported. For example, critical flicker frequency (CFF) and the peak of the modulation transfer functions increase with eccentricity (Hartman, Lachenmayer and Brettel, 1979; Virsu and Rovamo, 1979; Rovamo and Raninen, 1984; Tyler, 1985). We have previously documented, using electrophysiological and psychophysical techniques, that the locus of the increased temporal sensitivity of the peripheral retina begins at the level of the outer retina in humans (Seiple and Holopigian, 1996). In the current study, we examined whether the increased temporal detection sensitivity of the peripheral retina to uniformly illuminated targets was correlated with temporal aspects of letter identification. We also included a task which ensured central fixation in these experiments.