Abstract
Peripheral retinal contrast reduction is suggested as a potential myopia control strategy. However, the underlying mechanism is yet unknown. Therefore, this study investigated the influence of peripheral contrast reduction on central chromatic and achromatic contrast sensitivity (CS). A total of 19 participants were included. Peripheral contrast reduction was induced via Bangerter foils of 0.4 and 0.8 density, each with a clear central zone of 8.0 mm diameter. Central achromatic and chromatic (for S-, M-, and L-cone types) CS was measured at 3 and 12 cpd in a 2-IFC psychophysical procedure. CS was tested monocularly at 0, 30, and 90 min of adaptation time, while the fellow eye was covered by an infrared filter. With the filter in place, pupil size was controlled to be smaller than the clear central aperture. Data were analyzed using linear mixed models. Cone-type CS showed significant differences among each other (all p < 0.05), except for the achromatic and L-cone type (p = 0.87). The minimum sensitivity was found with the S-cone type and the maximum with the M-cone type. Central achromatic and chromatic CS were equally affected by diffusion. The level of peripheral diffusion also influenced CS, while the 0.8 Bangerter foil led to a higher reduction in CS compared to the 0.4 Bangerter foil (p = 0.0008) and the control condition (p = 0.05). A significant reduction in CS occurred between 30 and 90 min of adaptation time (p < 0.0001). The current study found that peripheral contrast reduction impacted central achromatic and chromatic CS equally. It further showed that the amplitude of reduction was influenced by the level of diffusion, with the reduction becoming more pronounced over time.
Highlights
Physiological ocular refraction changes during early life are known as refractive development
While hyperopia is common in newborns, it reduces during childhood, called emmetropization
Retinal contrast reduction is associated with retinal image degradation, based on various optical factors, such as defocus, astigmatism, higher order aberration, or scattering [12,14]
Summary
Physiological ocular refraction changes during early life are known as refractive development. If the emmetropization process is disturbed, hyperopia may persist or myopia and/or astigmatism may occur [1,2]. Emmetropization processes depend on multiple factors including the balance of central and peripheral visual experiences [3,4,5]. The peripheral retina might be of importance in the ability to derive blurred and diffused contrast signals [5], as well as in contrast adaptation processes [6,7,8,9,10,11,12,13]. The role of peripheral contrast reduction and the related contrast adaptation processes in refractive development have not yet been fully clarified
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