Abstract
Purpose: It is now well accepted that contrast sensitivity (CS) is the most comprehensive measure of human spatial vision. Previously (VSS 2015), we reported the first data for CS measurement in both the near and far periphery, using Gaussian filtered sine waves (Gabor patches). However, in order to better understand underlying neural mechanisms and to provide normative data for those interested in assessing peripheral eye disease (e.g. glaucoma, RP, retinal degeneration), here we measured CS across both the nasal and temporal retinal fields. Methods: Using a conventional staircase procedure, right eyes from 10 healthy emmetropic adults (16 to 55 yr.) were tested 10 times repeatedly with vertically-oriented sinusoidal Gabor patches that ranged logarithmically in spatial frequency (SF) from 0.375 to 18 cy/deg and in contrast from 0.001 to 0.30. Contrast thresholds at each SF were obtained foveally and from 100 to 800 within the temporal and nasal visual fields. Results: As expected, with increasing eccentricity, the drop-off in peripheral CS from foveal viewing (Mfoveal across SF = 145.9 CS units) is substantial. However, the pattern differs between the two fields: Nasal sensitivity drops off rapidly over the first 200 (to 10.5 units) but then completely stabilizes until 600 (10.6 units). In contrast, temporal sensitivity decreases more steadily but eventually yielding a lower CS level at 600 (5.6 units, p < 0.05). Conclusions: Human CS can be measured reliably up to 600 in both the nasal and temporal visual fields. Overall, CS decreases by about 0.24 log units per 10o eccentricity, but the rate of reduction is at first rapid and then plateaus in the nasal field, and is much more steady in the temporal field. These behavioural data are consistent with anatomical data describing the relative ratios of P ganglion cells in the peripheral retina.
Meeting abstract presented at VSS 2016