Change in visual acuity is highly correlated with change in six image quality metrics independent of wavefront error and/or pupil diameter

Abstract

It is well known that the wavefront error (WFE) of the eye varies from individual to individual, with pupil diameter and with age. Numerous studies have been proposed evaluating the relationship between visual acuity and WFE but all these studies were performed with either a fixed pupil diameter or natural pupil diameter. It is still not clear if metrics of image quality correlates well with visual acuity independent of pupil diameter. Here we investigated the correlation between the change in visual acuity and change in 30 image quality metrics for a range of optical quality typically established in normal eyes that varies both with age and pupil diameter. Visual acuity was recorded for four normal subjects using simulated blurred logMAR acuity charts generated from the point spread functions of different scaled WFEs for 6 different pupil diameters (2 to 7mm in 1mm steps). Six image quality metrics [log neural sharpness, log visual Strehl (spatial domain), log visual Strehl (MTF method), log pupil fraction (tessellated), log pupil fraction (concentric area) and log root mean square of WFE slope] accounted for over 80% of variance in change in acuity across all WFE’s and all pupil diameter. Multiple regression analysis did not significantly increase the R2. Simple metrics derived from wave front error could potentially act as an objective surrogate to visual acuity without the need for complex models.

A Comparison of Three Methods to Increase Scleral Contact Lens On-Eye Stability

“…For this model, it was assumed (but not proven) that the lens would behave similarly on other highly aberrated eyes as the two eyes with keratoconus measured here. The visual image quality metric visual Strehl, which has previously been demonstrated to be well-correlated with change in acuity by Ravikumar et al 17,18 , was used to quantify the predicted change in visual acuity that would be experienced in the presence of these movements.…”

“…The choice to evaluate the impact in terms of visual image quality was based on evidence in the literature that root mean square (RMS) wavefront error is relatively poorly correlated with visual acuity 12 and that measured change in visual quality metrics (in particular visual Strehl ratio and neural sharpness) are highly correlated to a measured change in visual performance as measured by acuity in the presence of keratoconus (KC) aberrations. 17,18 …”

Predicting Through-Focus Visual Acuity with the Eye’s Natural Aberrations

“…To minimize the reflections from the trial lens, subjects were instructed to tip their heads slightly. 20 Head tilt with a cylindrical lens would induce unwanted off-axis aberrations; therefore, only subjects with little to no refractive cylinder were included. The anterior and posterior corneal radius, corneal aberrations, and corneal thickness of each eye were measured using the Bausch + Lomb Orbscan IIz corneal topographer (Rochester, NY).…”

“…26 A more recent study completed by Ravikumar et al found high correlation to distance visual acuity when taking the log of image quality metrics presented by Thibos et al; specifically logNS, logVSX, logVSMTF, and logPFSt gave R 2 Q0.86. 19,20,24 These previous studies show good correlation to distance visual acuity but still present a need for a through-focus image quality metric that takes into account the eye's natural aberrations, pupil diameter, and residual accommodative amplitude. The goal of this work was to develop a new image quality metric that is highly correlated with through-focus visual acuity and can be easily related to clinical measurements.…”

“…23Y25 Very few studies have looked at the correlation of clinical measurements, such as visual acuity, with predicted image quality at multiple object distances and over a large range of natural aberrations and pupil diameters. 20,26 Despite the proliferation of wavefront sensors to fully characterize the optical quality of individual eyes at distance and as a function of accommodation, there is not yet a single-value metric that is highly correlated with an individual's through-focus clinical acuity. There is still uncertainty about how aberrations interact with one another as well as their impact on through-focus retinal image quality.…”