Individual differences in the shape of the nasal visual field

AbstractBetween-subject differences in the shape of the nasal visual field were assessed for 103 volunteers 21–85years of age and free of visual disorder. Perimetry was conducted with a stimulus for which contrast sensitivity is minimally affected by peripheral defocus and decreased retinal illumination. One eye each was tested for 103 volunteers free of eye disease in a multi-center prospective longitudinal study. A peripheral deviation index was computed as the difference in log contrast sensitivity at outer (25–29° nasal) and inner (8° from fixation) locations. Values for this index ranged from 0.01 (outer sensitivity slightly greater than inner sensitivity) to −0.7 log unit (outer sensitivity much lower than inner sensitivity). Mean sensitivity for the inner locations was independent of the deviation index (R2<1%), while mean sensitivity for the outer locations was not (R2=38%, p<0.0005). Age was only modestly related to the index, with a decline by 0.017 log unit per decade (R2=10%). Test-retest data for 21 volunteers who completed 7–10 visits yielded standard deviations for the index from 0.04 to 0.17 log unit, with a mean of 0.09 log unit. Between-subject differences in peripheral deviation persisted over two years of longitudinal testing. Peripheral deviation indices were correlated with indices for three other perimetric stimuli used in a subset of 24 volunteers (R2 from 20% to 49%). Between-subject variability in shape of the visual field raises concerns about current clinical visual field indices, and further studies are needed to develop improved indices

Contrast sensitivity perimetry data from adults free of eye disease

This data article contains data referenced in “Individual Differences in the Shape of the Nasal Visual Field” [1]. The data were gathered from volunteers free of eye disease ages 21–85 who were tested with Contrast Sensitivity Perimetry (CSP), which uses a stimulus resistant to effects of defocus and reduced retinal illumination. Some subjects were tested only once or a few times, and others were part of a longitudinal cohort with as many as 10 tests. Parameters from maximum likelihood estimation of psychophysical threshold at each tested location are included in the data file, along with the participant׳s sex, age at time of test, the center of their physiological blind spot, the duration of test, the time of day that the test was begun, and the starting contrast used for the psychophysical staircases. Keywords: Perimetry, Contrast sensitivity, Visual fiel

Visual Psychophysics and Physiological Optics Effect of Age and Glaucoma on the Detection of Darks and Lights

PURPOSE. We have shown previously that normal observers detect dark targets faster and more accurately than light targets, when presented in noisy backgrounds. We investigated how these differences in detection time and accuracy are affected by age and ganglion cell pathology associated with glaucoma. METHODS. We asked 21 glaucoma patients, 21 age-similar controls, and 5 young control observers to report as fast as possible the number of 1 to 3 light or dark targets. The targets were positioned at random in a binary noise background, within the central 308 of the visual field. RESULTS. We replicate previous findings that darks are detected faster and more accurately than lights. We extend these findings by demonstrating that differences in detection of darks and lights are found reliably across different ages and in observers with glaucoma. We show that differences in detection time increase at a rate of approximately 55 msec/dB at early stages of glaucoma and then remain constant at later stages at approximately 800 msec. In normal subjects, differences in detection time increase with age at a rate of approximately 8 msec/y. We also demonstrate that the accuracy to detect lights and darks is significantly correlated with the severity of glaucoma and that the mean detection time is significantly longer for subjects with glaucoma than age-similar controls. CONCLUSIONS. We conclude that differences in detection of darks and lights can be demonstrated over a wide range of ages, and asymmetries in dark/light detection increase with age and early stages of glaucoma. Keywords: retina, thalamo-cortical, light-dark, perimetry, psychophysics V isual information travels from the eye to the rest of the brain through two major pathways that signal light increments (ON) and decrements (OFF) in local regions of visual space. In mammals, ON and OFF channels remain segregated in the thalamus and combine for the first time in visual cortex. However, ON-OFF cortical mixing is incomplete and unbalanced. Although single cortical neurons receive input from both channels, ON and OFF thalamic afferents segregate in different cortical domains 1-4 and cortical current sinks generated by OFF thalamic afferents are stronger and occupy larger territory than those generated by ON afferents. Moreover, cortical responses to dark stimuli are stronger, faster, more linearly related to luminance contrast, and have better spatial and temporal resolution than responses to light stimuli. 27-30 To investigate if dark/light asymmetries are affected by glaucoma within the central 308 of fixation, we asked human observers to report the number of dark or light targets presented in binary noise on a monitor screen. Our results demonstrated that darks are detected more accurately and faster than lights in control observers and observers with glaucoma. Moreover, we showed that these dark/light asymmetries increase with age and in the early stages of glaucoma. METHODS We recruited 21 patients with open angle glaucoma (48-83 years old; mean, 64.7 6 7.5 years old), 21 control observers with a similar age range (49-74 years old; mean, 62.2 6 7.3 years old), and 5 young control observers (21-25 years old). The study was performed following the principles outlined in the Declaration of Helsinki. The inclusion criteria for all groups were: best corrected visual acuity of at least 0.2 logMAR units (approximately 20/30), spherical equivalent refractive error within À6 to þ2 diopters (D), cylinder correction within 3 D, clear ocular media, and absence o