Modeling optical and visual image quality across the retina

Abstract

Purpose : We aimed to 1) create anatomically plausible individual eye models for cohorts of emmetropic and myopic eyes that define wavefront error (WFE) across the visual field and 2) apply neural anatomical weighting functions to those WFE to model visual performance.

Methods : Discretely measured WFE of 24 emmetropic (spherical equivalent (SE) +0.5 to –0.5D) and 18 myopic eyes (SE –1.5 to –3.5D) obtained from 4 laboratories (ranging ±21 to ±40° horizontally and ±16 to ±25° vertically around fixation) were used to optimize anatomical eye models in Zemax. Models comprised biconic anterior and posterior corneal surfaces, gradient refractive index lenses with aspheric surfaces, and aspheric retinas. All 27 anatomical parameters (including thicknesses, tilts, and translations) were constrained within typical norms from literature. Visual field angles were converted to mm of (aspheric) retina per eye.

Results : Of the 8 emmetropic and 3 myopic eyes completed to date (optimizing 27 parameters takes multiple days per eye), models accurately reproduced 2^nd, 3^rd, and 4^th order input aberrations: mean ±SD total RMS difference 0.237 ±0.166um (4mm pupil). Foveal chromatic aberration of each model matched published population data to within 0.1D.
Mean field positions of best RMS WFE and Strehl ratio in emmetropic models were: RMS 1.4° and 0.3°; Strehl 2.0° and 0.6°, in inferior and nasal fields respectively, which agreed closely with input data. Optical quality generally worsened monotonically with eccentricity in all directions from those peaks. Peripheral optical quality in myopic eyes depended on the form of modeled refractive corrections.
Degrees-to-mm factors were non-linear with eccentricity in each eye and varied with retinal curvature, asphericity, and nodal point position across eyes.
Relative cone- and midget retinal ganglion cell-weighted metrics mimicked experimental literature on detection and resolution as functions of eccentricity respectively.

Conclusions : Optical and visual (neurally-limited) image qualities across the retina are valuable in understanding onset and progression of ametropias as well as guiding development of wide-field head-mounted displays, ophthalmic corrections, and retinal imaging technologies. These models are more anatomically accurate than previous, they effectively return measured input WFE, allow continuous interpolation of WFE as a function of eccentricity, and represent mean samples and variability of typical eyes.

This is a 2021 ARVO Annual Meeting abstract.