Impact of Forms of Visual Attenuation on Short-Term Eye Changes Under Controlled Reading Visibility

• Published in: Eye and Brain
• Main Authors: Su H, Chun RKM, De Lestrange-Anginieur E
• Format: Article
• Language: English
• Published: Dove Medical Press 2024-12-01
• Subjects: reading; crowding; myopia; axial length; choroidal thickness
• Online Access: https://www.dovepress.com/impact-of-forms-of-visual-attenuation-on-short-term-eye-changes-under--peer-reviewed-fulltext-article-EB

Huanjun Su,1,2 Rachel Ka Man Chun,1,3– 5 Elie De Lestrange-Anginieur1,3– 5 1School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong; 2Department of Optometry, Liuzhou Worker’s Hospital, Liuzhou, Guangxi Zhuang Autonomous Region, 545005, People’s Republic of China; 3Research Centre for SHARP Vision (RCSV), the Hong Kong Polytechnic University, Kowloon, Hong Kong; 4Laboratory of Experimental Optometry, Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong; 5Centre for Eye and Vision Research (CEVR), Hong Kong, Hong KongCorrespondence: Elie De Lestrange-Anginieur, School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, Tel [phone], Fax [phone], Email [e-mail]: Animal studies have suggested that visual degradation impacts eye growth due to the attenuation of high spatial frequencies. However, the influence of perceptual visibility remains unclear in humans. The aim of this study was to investigate the impact of visibility on visual attenuation-related eye changes during reading.Methods: Axial length (AxL) and choroidal thickness (ChT) changes associated with reading tasks were measured in two separate experiments. In the first experiment, the reading task was conducted under different forms of visual attenuation (contrast, resolution, defocus, noise, and crowding). For each form of visual attenuation, the text was set at a sub-threshold level of visibility, evaluated via prior measurement of reading performance, and kept constant via adaptive control of the intensity of the stimulation. Each sub-threshold reading condition was compared with a supra-threshold reading text, serving as control. In the second experiment, the effect of visibility on lens-induced defocus was further examined by comparing the effect of text stimulation with an equivalent dioptric of 5.5 D under sub- and supra-threshold levels of resolution.Results: Near distance reading with supra-threshold texts caused eye elongation (AxL: +12.942 μm ± 2.147 μm; ChT: − 3.192 μm ± 1.158 μm). Additional defocusing failed to exacerbate axial elongation under sub-threshold text visibility (mean difference: − 0.135 μm ± 2.783 μm), revealing a clear inhibitory effect of lowering visibility on eye changes. Other forms of visual degradation, including crowding (mean difference: 6.153 μm ± 2.127 μm) and noise (mean difference: 5.02 μm ± 2.812 μm) also showed an inhibitory effect on eye elongation. The significant effect of crowding indicated that post-retinal mechanisms, involving attentional processes related to crowded characters, may play a role in the influence of visibility.Conclusion: Although the featural composition of visual stimulation can drastically influence eye changes, this study revealed an important mediating role of visibility, previously underscored in chick studies, which warrants further explorations of the impact of post-retinal processes in eye growth.Keywords: reading, crowding, myopia, axial length, choroidal thickness