Abstract
Purpose: Increased intraocular scattering degrades vision due to a reduction of contrast in the retinal images. This may also have an impact on accommodation. The aim of this study is to investigate the relationship between increased scatter and accommodation performance.
Methods: An open-view binocular sensor [Chirre et al., Opt. Lett., 39, 4773, (2014)] operating in real time (25Hz) with an invisible infrared beam (1050 nm) was used to measure accommodation, pupil size and aberrations in both eyes simultaneously. Six young subjects (29.5 ±2.6 years old) without any known ocular anomaly were measured while accommodating monocularly with their dominant eye from far (3 m) to a near (0.3 m) target through scattering diffusers. Accommodation was measured in the contralateral eye, not covered with the diffuser nor exposed to the stimuli. Six diffuser conditions were tested: no filter (baseline), 0.1 and 0.6 Bangerter foils (Ryser Optik, St. Gallen, Switzerland), BlackProMist 2, ProMist 1, and the combination of ProMist1 and ProMist2 (Tiffen Company, Hauppauge, NY, USA). All of them were characterized by means of a single-pass optical integration method [Ginis et al., J. Vis. 12(3), 20, (2012)].
Results: A very good correlation (R2 = 0.94) was found between the scatter coefficient induced by each filter and the average lag of accommodation. For the densest filter (0.1 Bangerter foil), the average loss of accommodative response was 0.64±0.62 D, with values close to 1.5 D for one subject. The increase in the lag of accommodation is mainly produced by under-accommodation to the near stimulus although for the 0.1 Bangerter foil most subjects also found difficulties to relax their accommodation when the stimulus is placed at far.
Conclusions: Intraocular scattering, which is known to reduce the contrast of the retinal images, impairs the performance of the accommodation response. We have found a high correlation between the amount of induced scattering and the increase in the lag of accommodation. In early presbyopic subjects with elevated scatter, this effect could be a factor in age-related loss of accommodation.
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