Myopia is increasing worldwide hence it exists a pressing demand to find effective myopia control strategies. Previous studies have shown that light, spectral composition, spatial frequencies, and contrasts play a critical role in refractive development. The effects of light on multiple retinal processes include growth regulation, but also visual performance and perception. Changes in subjective visual performance can be examined by contrast sensitivity (CS). This study was conducted to investigate whether retinal light stimulation of different wavelength ranges is able to elicit changes in CS and, therefore, may be used for myopia control purposes. In total, 30 right eyes were stimulated with the light of different wavelength ranges, including dominant wavelengths of ∼480 nm, ∼530 nm, ∼630 nm and polychromatic light via a commercial liquid crystal display (LCD) screen. Stimulation was performed screen full-field and on the optic nerve head only. CS was measured before any stimulation and after each stimulation condition using a novel and time-efficient CS test. Post-stimulation CS changes were analyzed by ANOVA regarding the influencing factors spatial frequency, stimulation wavelength and stimulation location. A priorly conducted verification study on a subset of five participants compared the newly developed CS test to a validated CS test. The novel CS test exhibited good reliability of 0.94 logCS and repeatability of 0.13 logCS with a duration of 92 sec ± 17 sec. No clinically critical change between pre- and post-stimulation CS was detected (all p>0.05). However, the results showed that post-stimulation CS differed significantly at 18 cpd after stimulation with polychromatic light from short-wavelength light (p0.05). To summarize, a novel CS test measures the relationship between retinal light stimulation and CS. However, using retinal illumination via LCD screens to increase CS is inconclusive.

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.

A novel combination device for objective and subjective refraction was assessed regarding repeatability, reproducibility, validity, vision quality, and timing for experienced and untrained examiners. Six examiners (each three trained optometrists and untrained examiners) examined 33 healthy participants for objective and subjective refraction. The ZEISS VISUCORE 500 (VC) objective and subjective refraction combination device with an algorithm-based guided and regular custom mode was compared to a conventional control procedure (wavefront aberrometer and phoropter). For the objective measurement of spherical equivalent refractive error (SE), VC shows good repeatability (≤ ±0.29 D) and reproducibility (≤ ±0.28 D) across all examiners versus control (±0.34 D and ≤ ±0.30 D, respectively), measured only by trained examiners. VC measures slightly negative objective refractions for SE with a mean difference (MD) and 95% limits of agreement (LoA) of -0.07 ± 1.24 D analyzed for a trained examiner. Subjective refraction for VC guided and custom mode showed good repeatability (≤ ±0.64 D) and reproducibility (≤ ±0.59 D) regarding SE for the examiner level. The results were similar to control (±0.54 D and ±0.51 D, respectively) with MD and LoA of +0.12 ± 0.67 D and +0.14 ± 0.66 D for VC guided and custom for trained examiner level. No significant differences were observed in best-corrected visual acuity across the three refraction workflows (all p > 0.05). The VC guided procedure was the most time-efficient, requiring less than 5 min of chair time. The tested combination refraction device provides reliable and efficient objective and subjective refraction measurements across trained and untrained examiners.