The Stiles-Crawford Effects and their Significance in Vision. In: Jameson D, Hurvich LM, editors. Visual Psychophysics. Berlin: Springer Berlin Heidelberg; 1972. pp. 470-83. [DOI: 10.1007/978-3-642-88658-4_18]

Spatial contrast sensitivity from star- to sunlight in healthy subjects and patients with glaucoma

Glaucoma is traditionally considered an asymptomatic disease until later stages. However, questionnaire studies revealed visual complaints related to various tasks, especially under extreme luminance conditions (such as outdoor at night on an unlit road or outside in the sun). We measured contrast sensitivity (CS) over a luminance range of 6 log units spanning the scotopic to photopic range and we aimed (1) to determine whether Weber's law also holds under extremely high luminance conditions and (2) to compare CS as a function of spatial frequency and luminance between glaucoma patients and healthy subjects. We included 22 glaucoma patients and 51 controls, all with normal visual acuity. For the second aim, we used a subgroup of 22 age-similar controls. Vertically oriented sine-wave gratings were generated with a projector-based setup (stimulus size 8x5 degrees). CS was measured monocularly at 1, 3, and 10 cycles per degree (cpd); mean luminance ranged from 0.0085 to 8500 cd/m². ANOVA was used to analyze the effect of glaucoma, luminance, and spatial frequency on logCS. In controls, Weber's law held for 3 and 10 cpd; for 1 cpd, CS dropped above 1000 cd/m² (P = 0.003). The logCS versus log luminance curves did not differ grossly between patients and controls (P = 0.14; typically 0-0.2 log units); the difference became larger with decreasing luminance (P = 0.003) but did not depend clearly on spatial frequency (P = 0.27). We conclude that differences between glaucoma and healthy were relatively modest for the spatially redundant, static stimulus as used in the current study.

Evidence against age-related enlargements of ganglion cell receptive field centers under scotopic conditions

Age-related changes in the neural organization of spatial information are required to account for much of the senescent loss in human scotopic spatial vision, specifically declines in the high spatial frequency cut-off of the contrast sensitivity function and enlargements of the area over which there is complete spatial summation (Ricco's area). These results are consistent with hypothesized enlargements of ganglion cell receptive field centers during adulthood. This hypothesis was tested with 50 subjects (19-88 years) by measuring contrast thresholds for two low spatial frequency gratings (0.3 and 1.2 cycles per degree) at a series of scotopic mean illuminance levels. Contrast sensitivity increased with retinal illuminance and then reached a plateau, corresponding to the onset of Weber-like behavior. No age-related change in the light level associated with the onset of Weber-like behavior was found at either spatial frequency. This result is inconsistent with proposed age-related enlargements of ganglion cell receptive field centers under scotopic conditions.

Senescent changes in scotopic contrast sensitivity

Scotopic contrast sensitivity functions (CSFs) were measured for 50 observers between the ages of 20 and 88 years. Using a maximum-likelihood, 2-alternative, temporal forced-choice threshold-estimation algorithm, scotopic CSFs were measured at 7 spatial frequencies ranging from 0.2 to 3.0 cpd, with mean retinal illuminance equated for observers at -0.85 log scotopic Trolands. For each stimulus condition, eight cycles of a horizontal sinusoidal grating were presented within +/- 1 S.D. of a 2-D Gaussian-spatial envelope and within a 1-s Gaussian-temporal envelope. Stimuli were centered on the nasal retina along the horizontal meridian 6 degrees from the fovea. Scotopic CSFs were found to be low-pass. Statistically significant age-related declines in contrast sensitivities were found for spatial frequencies at or below 1.2 cpd. There was also a statistically significant decrease in the high frequency cut-off with age (P < 0.01). An explanation of these results in terms of optical factors is rejected, while the results are consistent with age-related changes in the magnocellular pathway.

Effect of pupil size and astigmatism on contrast acuity with monofocal and bifocal intraocular lenses

We conducted a bicenter study to evaluate the effect of pupil size and corneal astigmatism on best corrected contrast acuity (BCCA) in patients with the True Vista bifocal intraocular lens (IOL) and compared the results with those in a matched group of monofocal patients. Best corrected contrast acuity was measured using the Regan Charts (96%, 50%, 25%, 11%) at four pupil sizes (2.0, 2.5, 3.5, 6.0 mm) in three groups (Group 1: corneal astigmatism 0-0.50 D [n = 11]; Group 2: 0.75-1.50 D [n = 11]; Group 3: 1.75-2.50 D [n = 4]). In monofocal eyes, BCCA between these astigmatic groups did not differ significantly at any contrast step or at any pupil size tested. However, BCCA decreased slightly with increasing pupil size in each group, and differences between 2.00 mm and 6.0 mm pupils were significant at each contrast level. In all bifocal groups, BCCA decreased significantly with increasing pupil size and also decreased with increasing corneal astigmatism; differences were significant at most pupil sizes and contrasts tested. In Group 1, BCCA was lower in eyes with bifocal IOLs than in eyes with monofocal IOLs at 25% and 11% contrast with a 2.5, 3.5, and 6.0 mm pupil; with a 2.0 mm pupil it did not differ significantly. In Groups 2 and 3, BCCA in eyes with bifocal IOLs was lower at all contrast steps and all pupil sizes tested. Our results indicate that corneal astigmatism in excess of 0.50 D reduces quality of vision in eyes with bifocal IOLs, while eyes with monofocal IOLs are not affected.(ABSTRACT TRUNCATED AT 250 WORDS)