The effect of improving the eye's optical quality on spatio-temporal contrast sensitivity

Abstract

Purpose : The impact of the eye’s optical quality on spatial vision has been investigated extensively, but optical contributions to temporal vision are relatively unknown. A recent study showed that flicker affects spatial vision (Arnold, et.al, 2016). Motivated by work on interactions between spatial and temporal pathways, we examined whether spatial improvement achieved by adaptive optics (AO) also affects temporal vision. Specifically, how spatial contrast is perceived in the presence of flicker.

Methods : Spatial contrast sensitivity of three human observers was measured with vertically oriented sine wave gratings of 1 and 16 c/deg flickering at 0, 4, 16, 32 or 48 Hz for 500ms. Sensitivity was measured with habitual uncorrected ocular aberrations and with full aberration correction using AO. Improvement in performance owing to better spatial vision was expressed as the ratio of the difference between contrast sensitivity (CS) in the two optical conditions (AO and habitual) over the average: (CS_AO – CS_Habitual) / (CS_AO + CS_Habitual).

Results : Without flicker, contrast sensitivity at 1c/deg was similar in the two optical conditions, but generally higher with AO correction at 16c/deg, replicating prior results (average habitual sensitivity: 40±19; average AO sensitivity: 65±45). For high spatial frequencies, AO helped performance for 0Hz stimuli, but this improvement diminished with increasing temporal frequency, turning into a deficit for some subjects (r=-0.98). Slopes of the diminishing improvement varied among individuals due to differences in subjects’ habitual aberration. At the high flicker rates (32 and 48Hz), improving the optics of the eye almost no impact on spatial contrast sensitivity.

Conclusions : AO correction provides greater improvement at high spatial frequency and low flicker rates but no improvement at high flicker rates. These findings suggest that spatial channels affect threshold-level temporal vision at low but not high flicker frequency. Hence, optical imperfections in well-focused eyes do not limit contrast detection at high temporal frequencies.

This is a 2020 ARVO Annual Meeting abstract.