Abstract
Purpose :
Astigmatism before visual development results in abnormal visual development due to principal meridional variations in visual processing. The current study aims to 1) assess the contrast sensitivity function (CSF) in two principal meridians, and 2) evaluate the effects of perceptual learning on CSF and visual acuity in patients with astigmatism.
Methods :
Ten subjects with with-the-rule astigmatism (mean age = 13.90 ± 1.73 years) participated in baseline assessments, which consisted of visual acuity and CSFs measured with both vertical and horizontal sinewave gratings. They were then trained in a luminance grating orientation identification task (±5°) around either the vertical or horizontal direction at their individual cutoff spatial frequency, whichever had relatively poorer CSF. Post-training assessments were the same as the baseline.
Results :
Results from the baseline tests showed that the cut-off spatial frequency on the horizontal meridian was lower than that on the vertical meridian (two-tailed paired t-test, t9=1.94, p=0.084), demonstrating differential effects of astigmatism on visual processing in different meridians. In addition, training in the weaker vertical meridian near each individual’s cut-off SF led to significant improvements in contrast sensitivity at the trained SF measured with vertical sinewave gratings (4.50 dB or 67.96%; two-tailed paired t-test, t9=2.81, p=0.020). No significant improvement was found in contrast sensitivity at the trained SF measured with horizontal sinewave gratings. Moreover, the training improved visual acuity of the trained eye by 3.70 dB (or 53.17%).
Conclusions :
Patients with astigmatism showed meridional variations on CSF along their principal meridians at baseline. Perceptual training in the “weaker” principal meridian improved VA due to the improved CSF in the weaker meridian and reduced difference between the two meridians. These findings demonstrate effects of astigmatism on visual processing and provide empirical evidence for perceptual learning as a potential treatment for astigmatism.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.