Advances in photoreceptor quantification moving from conventional to high-resolution SPECTRALIS optical coherence tomography

Abstract

Purpose : High-Resolution SPECTRALIS OCT is based on a shorter central wavelength and a larger spectral bandwidth providing an axial resolution of up to 3 µm compared to 7 µm in conventional OCT imaging with an identical lateral resolution. The purpose of this study was to investigate efficacy in retinal morphology accessibility on the photoreceptor (PR) level in intermediate age-related macular degeneration (iAMD).

Methods : Patients with iAMD were imaged using a 6x6mm scan pattern (97 B-scans) for standard SPECTRALIS HRA+OCT and the investigational device SPECTRALIS High-Res OCT, both by Heidelberg Engineering, Germany. PR thickness was measured using a previously trained deep learning algorithm for segmenting PR layer (inner border of the ellipsoid zone to retinal pigment epithelium) and manually corrected if necessary. Overall PR thickness and drusen maps were computed for all patients. PR loss area and thickness were compared between devices and areas using mixed effect models.

Results : Twenty-nine eyes from 23 patients were included. Mean PR loss in the central 1 mm area was higher on the standard OCT with 0.07 mm² compared to 0.04 mm² on the High-Res OCT (p=0.049). Parafoveal (1-3 mm) PR loss was 0.32 mm² and 0.16 mm² on the standard OCT and the High-Res OCT, respectively (p=0.032). Perifoveal (3-6 mm) PR loss was 0.08 mm² on the standard OCT and 0.05 mm² on the High-Res OCT (p=0.029). Mean overall PR thickness was 26.46 µm on the standard OCT compared to 32.23 µm on the High-Res OCT. Mean PR thickness in drusen areas was 26.30 µm and 32.39 µm in non-drusen areas. The PR layer was generally thinner on the standard OCT (p<0.001) and in drusen areas (p<0.001).

Conclusions : High-Res OCT with superior axial resolution is able to identify the condition of the PR level in iAMD with higher precision. High resolution improves the distinction of retinal layers on OCT imaging promoting the understanding of retinal disease particularly in its early stage. Higher axial resolution might therefore be better suited to investigate disease pathomechanisms, progression to advanced macular atrophy and valid therapeutic targets.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1: Patient with intermediate AMD. OCT B-scan on HRA+OCT (A) and on High-Res OCT (B). Example of non-congruence of PR thickness between the HRA+OCT (C) and High-Res OCT (D).