Macular Layer Thickness with Spectral-Domain and High-Resolution OCT

The new generation high-resolution OCT (HR-OCT) offers higher axial resolution compared to standard spectral-domain OCT (SD-OCT). This study aimed to determine whether potential differences in the segmentation of retinal layers in the macula with the 2 techniques could lead to clinically meaningful differences with implications for monitoring progression when patients are switched to HR-OCT.

Prospective cross-sectional study.

This study included glaucoma patients and healthy control subjects.

Each eye underwent SD-OCT followed by HR-OCT, with both macular scan patterns acquired at the same transverse location. Automated segmentation was applied and the thickness of 6 individual retinal layers calculated for 1024 A-scans for each of 97 B-scans. Intradevice difference was also assessed with repeated scans.

Differences in retinal layer thickness measurements between SD-OCT and HR-OCT.

A total of 68 eyes (both eyes of 17 glaucoma patients and 17 healthy control subjects) underwent imaging. Mean differences in retinal layer thickness between SD-OCT and HR-OCT ranged from -2.65 to 2.02 μm. Hyper-reflective layers were thicker with SD-OCT, while hyporeflective layers were thicker with HR-OCT, showing an alternating pattern in interdevice differences in thickness measurements. Intradevice differences in thickness measurements, evaluated in a subset of 10 eyes of 5 participants, were within ± 1 μm. Image quality was not an important predictor of the interdevice thickness differences (R² < 0.08).

Interdevice differences in retinal layer thickness were small but consistent. The alternating pattern is likely due to the lower axial resolution of SD-OCT making hyper-reflective layer borders blurred and consequently thicker. For follow-up, patients can be switched to HR-OCT from SD-OCT; however, depending on the magnitude of change required for detection, the differences between the 2 techniques could potentially mask or masquerade change.

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.