Evaluation of a combined anterior segment OCT and aberrometer using the same light source

Abstract

Purpose : The design of the current intraoperative OCTs and aberrometers prevent their combined use. The purpose of this study is to demonstrate the proof-of-concept of a combined anterior segment OCT and aberrometer that addresses this barrier by using a single light source.

Methods : We built a combined SD-OCT system and Hartmann-Shack (HS) aberrometer that uses a single light beam. The system operates at a wavelength of 840nm. The beam is focused in the pupil plane to produce high-contrast OCT images of the anterior segment. The HS sensor collects part of the light returning from the retina to measure aberrations. The difference with standard HS aberrometers is that the beam reaching the retina is defocused. We tested the aberrometer on a model eye that provides controlled amount of defocus and cylinder in the range between -16D and +32D and -5D to +5D, respectively. To assess the accuracy of the system, we compared the power vectors (M, J0 and J45) measured on 11 human subjects (total eyes = 22, age range: 29.73 ± 10.11 y/o, SE range: -9D to 0D) to those obtained using a clinical autorefractor (KR-800, Topcon). To evaluate intrasession repeatability, we acquired 5 consecutive refraction measurements on the right eye of a 43 y/o subject (SE = -3D). The same operator acquired 5 measurements on the same subject at 30-minute intervals to assess intersession repeatability. Each session consisted of 5 consecutive measurements.

Results : The aberrometer provides a linear measurement response (y = 1.006x + 0.0054) with residuals of less than ±0.35D in the sphere range of the eye model. The maximum absolute differences between theoretical and measured values of cylinder at the end of the cylinder range are 1.25, 0.40 and 1.85 D, for -16, 0 and +32D values of spheres, respectively. Correlation plots from Bland-Altman analysis (Fig. A) show mean differences between the measurements obtained with the two systems of 1.03, 0.08 and 0.03D for M, J0 and J45, respectively. The 95% confidence limits of agreement were ± 1.29, ± 1.02 and ± 0.63 D (M, J0 and J45). Intra- and Inter-session repeatability analysis yielded standard deviations of 0.02, 0.21, 0.24 D (M, J0, J45) and 0.11, 0.25, 0.21 D (M, J0 and J45), respectively. Fig. B shows a full-depth OCT image of the anterior segment of a 50 y/o subject.

Conclusions : We demonstrated the proof-of-principle of combined anterior segment OCT and autorefraction using a single beam.

This is a 2020 ARVO Annual Meeting abstract.