Abstract
Purpose :
A small pupil increases the depth of focus, reduces the impact of aberrations, and limits leakage of light across the retina. Here, we examine how adult vision perceives light in monocular viewing conditions through a small flickering pupil using a modified integrated Stiles-Crawford (SC) test system with a digital micromirror device (DMD) for both projected pupil size and brightness control. The goal is to understand how angular apodization impacts on vision in bright light and its possible relation to myopia onset.
Methods :
The integrated Stiles-Crawford effect was measured directly with a flickering pupil size system [Vohnsen et al. J. Vision 17, 18 (2017)] using an upgraded projection method with a DMD V7001 *(VialuxTM) where brightness is varied by the flicker duty cycle [Carmichael Martins & Vohnsen, OPO 38, 3 (2018)]. Three emmetropic subjects (the authors, age: 22, 25 and 54 years) were examined at wavelengths of 450, 550, and 650 nm using a variable bandwidth tunable optical filter (MeadowlarkTM) in combination with tungsten-halogen lamp. Using a 2-degree test pattern, the effective visibility with pupil sizes up to 6.6 mm was measured with respect to a 1.6 mm reference matching that of corneal inlays both for foveal vision at an eccentricity of 5 visual degrees. The measured effective visibility was compared to that of absorption across the cone photoreceptors using a raytracing model with absorption (ComsolTM) with a simplified Navarro eye model.
Results :
We find that the integrated SC visibility function decreases rapidly with increasing pupil size and matches that of an inverse power law. Its wavelength dependence is weak varying less than 10% for the wavelengths studied for all 3 subjects. The integrated SC effect at the fovea agrees with a strong integrated SC truncation whereas at the 5 degree retinal eccentricity the effective integrated SC truncation is slightly reduced by up to 30%. The results compare well to those of the absorption model using Beer-Lambert's absorption law across the photoreceptors.
Conclusions :
With the modified DMD-based integrated SC characterization system we have determined subjective visibility both at the fovea and at a slight peripheral retinal location in three emmetropic subjects. The results show a likely linkage with outer photoreceptor segment length and therefore a potential role of pupil size in the protection against myopia onset.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.