The development of meridional anisotropies in neurotypical children with and without astigmatism: Electrophysiological and psychophysical findings

• Published in: Vision research (Oxford) Vol. 222; p. 108439
• Main Authors: Yap, Tiong Peng, Luu, Chi D., Suttle, Catherine M., Chia, Audrey, Boon, Mei Ying
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2024
• Subjects: Amblyopia; Amblyopia - physiopathology; Astigmatism; Astigmatism - physiopathology; Child; Child, Preschool; Children visual development; Evoked Potentials, Visual - physiology; Female; Horizontal effect; Humans; Longitudinal Studies; Male; Meridional anisotropies; Myopia; Olique effect; Psychophysics; Refractive error; Visual Acuity - physiology; Visual evoked potentials; Children visual development; Refractive error; Amblyopia; Myopia; Olique effect; Visual evoked potentials; Meridional anisotropies; Horizontal effect; Astigmatism
• ISSN: 0042-6989; 1878-5646; 1878-5646
• DOI: 10.1016/j.visres.2024.108439

•Human visual processing has biased sensitivities to gratings in various orientations.•Adults are usually least sensitive to oblique gratings (Oblique Effect).•Children are usually least sensitive to horizontal gratings (Horizontal Effect).•The horizontal effect is still present after four months with normal maturation.•Poor visual development may produce alternative patterns of meridional anisotropies. It is important to understand the development of meridional anisotropies in neurotypical children since those with poor visual development, such as amblyopia, can have different patterns of meridional anisotropies. While the oblique effect is usually observed in adults, neurotypical children who have normal 20/20 visual acuity tend to demonstrate a horizontal effect electrophysiologically. In this longitudinal study, orientation-specific visual evoked potentials (osVEPs) and psychophysical grating acuity were used to investigate the changes in the meridional anisotropies in children aged 3.8 to 9.2 years over two visits averaging four months apart. While it was hypothesized that the electrophysiological horizontal effect may shift towards an oblique effect, it was found that the electrophysiological horizontal effect persisted to be present in response to the suprathreshold moderate contrast 4 cycles-per-degree grating stimuli. Psychophysical grating acuity, however, demonstrated an oblique effect when assessed binocularly. In addition, a significant effect of visit, representing an increase in the average age over this period, was observed in the average osVEP C3 amplitudes (4.5 μV) and psychophysical grating acuity (0.28 octaves or approximately 1-line on the logMAR chart). These findings are relevant when evaluating amblyopia treatments and interventions, as it confirms the necessity to take into account of the effect of normal maturation and learning effects when evaluating young children. Special attention should also be given to children with early-onset myopia and high astigmatism even when their visual acuity is 20/20 as the electrophysiological findings are suggestive of poor visual development, which warrants further investigation.