Reproducibility of Full-Field OCT-based Optoretinography (ORG)

Abstract

Purpose : Optical retinography (ORG) is a new technique for imaging the response of the retina to a light stimulus. The reaction of the tissue leads to changes of the optical phase in the scattered light, which can be measured with OCT. Recently it was shown, that full-field swept-source (FF-SS) OCT can quantify the ORG response not only in photoreceptor outer segments but also in different strata of the inner plexiform layer (IPL). The aim of this study was to evaluate the reproducibility of FF-SS-OCT-based ORG in healthy volunteers.

Methods : For all measurements a FF-SS-OCT was used, which consists of a tunable light source (Superlum Broadsweeper, BS-840-1) with 51 nm tuning range (λ0 = 841 nm, axial resolution of 8.4 μm air) and a ultra-high speed camera (Fastcam SA-Z, Photron) at a frame rate of 60 kHz (640 × 368 pixels).
Healthy volunteers were measured while a square of 1 mm edge length was stimulated with white light at an irradiance of 57 nW/mm². The head of the subjects was placed in a standard chin rest. No pupil camera or eye tracker, but only a simple mark or light spot was used for fixation. Continuous measurements were done under mydriasis over a time span of 8 seconds in six volunteers. Measurements were repeated 5 to 7 times for each subject.

Results : In all volunteers, usable ORG signals from the photoreceptor and the IPL could be measured. For photoreceptors each of the individual 33 measurement was successful (100% success rate). In the IPL measurements were more difficult due the signal magnitude being just a tenth in comparison to the photoreceptor signal and motion artifacts caused by the superficial vascular and intermediate capillary plexi. Here, a measurement success rate of 84% was achieved.

Conclusions : Although phase-based ORG is very sensitive to motion and the signal were continuously recorded over 8 seconds, functional measurements in photoreceptors and the IPL are possible with FF-SS-OCT in untrained healthy volunteers. No special immobilisation of the head is needed. Motion correction was possible in-silico without using any eye tracker. These results demonstrate that FF-SS-OCT based ORG should be possible in a clinical setting.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.