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Peripheral resolution acuity for achromatic gratings is known to be limited by the density of the underlying ganglion cell sampling array. After confirming isolation of the short-wavelength sensitive (SWS) system using chromatic adaptation methods, we wished to determine if resolution is limited by blue/yellow ganglion cell sampling (evidenced by a(More)
Turning off a fixation point prior to or coincident with the appearance of a visual target reduces the latency of saccades to that target. We investigated this 'gap effect' when subjects fixated a central point or the center of a square formed by four points that were 4, 2 or 1 degree eccentric from the square's center. The fixation anchor vanished 200 ms(More)
Transcranial magnetic stimulation (TMS) was used to investigate the delays in visual processing time produced by changes in luminance. By administering a magnetic pulse over the occipital pole 80-140 ms after the onset of visual stimuli, we could suppress perception of a four-digit number within a 30 ms time window. Commensurate with previous studies of(More)
Previous studies have indicated that peripheral achromatic grating resolution is limited by the sampling density of the neural array (sampling limited), and largely unaffected by large amounts of optical defocus and significant changes in luminance. Under certain conditions, peripheral short-wavelength sensitive (SWS) grating acuity is also sampling(More)
SUMMARY Fixation of subjects is assumed to be stable during perimetry, although few studies have addressed the nature of fixation over prolonged test periods. In this study, the horizontal eye movements of 12 normal subjects were measured using an infrared eye monitor while they performed automated thresholds. Our results indicate that no observer can(More)
PURPOSE To describe a normative database for the multifocal VEP (mfVEP) and to evaluate specificity for a range of cluster criteria. METHODS One hundred persons (62 females and 38 males) with normal visual fields and ranging in age from 21.6 to 92.4 years participated in this study. Self-reported race in 80 of these 100 persons was 'White or Caucasian,'(More)
PURPOSE To compare the diagnostic performance of multifocal visual evoked potential (mfVEP) and standard automated perimetry (SAP), in eyes with high-risk ocular hypertension or early glaucoma. METHODS Both eyes of 185 individuals with high-risk ocular hypertension or early glaucoma were evaluated. Subjects ranged in age from 37 to 87 (mean +/- SD: 61 +/-(More)
PURPOSE To investigate whether there is significant selective reduction in short-wavelength-sensitive (SWS) ganglion cell density in early to moderate glaucoma. METHODS Peripheral achromatic resolution acuity (an indirect measure of the underlying midget ganglion cell density) and peripheral chromatic resolution acuity under conditions of blue cone(More)
The purpose of the present study was to compare standard multifocal visual evoked potential (mfVEP) pattern-reversal responses with those produced by pattern-onset, pattern-offset, and pulsed pattern stimuli. mfVEP recordings were obtained from five normal subjects using VERIS and a 4-electrode array. The standard reversal stimulus had 2(15) m-sequence(More)
PURPOSE Visual field testing uses high-contrast stimuli in areas of severe visual field loss. However, retinal ganglion cells saturate with high-contrast stimuli, suggesting that the probability of detecting perimetric stimuli may not increase indefinitely as contrast increases. Driven by this concept, this study examines the lower limit of perimetric(More)