Abstract
Purpose :
The subjective estimation of astigmatism, part of the subjective refraction, is a tiresome procedure. Here we extend the Direct Subjective Refraction (DSR), a technology to obtain fast and unsupervised subjective measurements of the refractive error, to estimate astigmatism
Methods :
In the DSR method, a temporal defocus wave (TDW; fast and periodic changes in defocus induced by a tunable lens projected onto the eye) interacts with the longitudinal chromatic aberration of the eye. The flicker and color artifacts that appear on a stimulus, are minimum when TDW matches the retinal plane, so the patients can find subjectively their refractive error, unsupervised, with a staircase procedure. The stimulus for astigmatism is a set of magenta, red and blue lines, tested parallel and perpendicular to the axis of astigmatism reported by an autorefractometer (ARK1 Nidek). The TDW was produced by a visual simulator (SimVisGekko 2EyesVision) with frequency 15Hz and amplitude 0.5D. 4 subjects (25-49yo) performed the DSR with free accommodation in both eyes, 4 repetitions, 2 axes. The mean difference between axes provided the amount of astigmatism (J0, J45). DSR was compared with traditional subjective refraction (TSR) performed by an optometrist. Visual function with the DSR and the TSR corrections were evaluated with VisualAcuity (VA), StereoAcuity (SA), and direct comparison of perceived visual quality
Results :
DSR was able to measure small astigmatisms with high repeatability (SD average across repetitions and subjects ±0.13D). Comparing DSR with TSR, M, J0 and J45 components showed high correlation (p=5e-16, 5e-12, 9e-12; r=0.98, 0.98, 0.94). The mean difference in astigmatism (J0:0.08±0.11D, J45:0.01±0.06D) and the 95%CI Limits of Agreement (J0:[-0.14 to 0.30], J45:[-0.11 to 0.14] D) have subclinical importance. Both final refractions produce similar VA (mean difference -0.1±0.01logMAR; paired t-test p=0.35) and SA (29±8’’; p=0.4). On average, TSR takes 4.9±1.5 min while each repetition of DSR takes 47 seconds (per eye, including sphere). In direct comparisons, 50% of subjects preferred the final correction with DSR over with TSR
Conclusions :
Using temporal defocus waves, DSR is able to measure astigmatism, providing similar values than the TSR, but more repeatable. Each unsupervised DSR measurement (sphere and astigmatism) takes less than one minute, allowing clinicians to spend more time evaluating other visual aspects
This is a 2021 ARVO Annual Meeting abstract.