Abstract
The visual system’s response to complex stimuli can be estimated from the contrast sensitivity function (CSF), which varies across the visual field. Measuring this field of contrast sensitivity (Watson, 2018) has significant value, but requires too many measurements for practical applications. However, simplification may be possible via a spatial scaling factor (Stras-burger et al, 2011). We measured detection thresholds in 6 normally-sighted observers with Laplacian of Gaussian (LoG) stimuli at 3 eccentricities (4°, 9°, 19°) and 8 angular locations in two 8AFC tasks. In a behavioral task, observers reported the location of the target via button press; in a continuous-eye movement task, observers foraged for targets and each saccade landing point was scored as a directional response and became the fixation for the next trial. For faster evaluation, two points on the CSF were measured and then the contrast sensitivity function was fit with an asymmetric log-parabola (Watson & Ahumada, 2005) with upper and lower bandwidths fixed (Chung & Legge, 2016). First, visual acuity was measured at each location, then contrast sensitivity was measured 1.16 log10 units below the measured acuity. There were no significant differences between thresholds measured with behavioral and eye-movement methods, suggesting that these methods are interchangeable and the ease of comprehension of the eye movement task may favor its use in naive populations. Log Acuity decreased linearly with eccentricity (p< 0.001). Peak contrast sensitivity was constant as a function of eccentricity (p>0.05), which we attribute to the scaled nature of the LoG stimuli. The CSF in healthy eyes was therefore determined by visual acuity. Therefore, in healthy visual systems and scaled visual stimuli, the field of contrast sensitivity function can be estimated from the field of acuity resolution and this may provide a simple reference to rapidly detect visual field deficits in visually impaired populations.
Acknowledgement: CFA: NIH K99 EY026130 AK: NIH F32 EY028814 PJB: NIH R01 EY029713