Comparison of Rates of RNFL Change Between Two Optical Coherence Tomography Devices

Abstract

Purpose : To compare rates of retinal nerve fiber layer (RNFL) thickness change between two commercially available optical coherence tomography (OCT) devices.

Methods : Ninety-five eyes (95 patients) with central visual field (VF) damage with ≥2 years of follow-up and ≥4 visits were included. RNFL OCT was acquired with Spectralis spectral-domain OCT (single circle) and Cirrus high-definition OCT (Optic Disc Cube 200×200) on the same visit. Rates of change of RNFL thickness globally and in 12 clock hour sectors were estimated with simple linear regression (SLR). Outcomes of interest were absolute rates of RNFL change and the proportion of significant negative (slope<0 and p<0.05) and positive (slope>0 and p<0.05) RNFL slopes. We also identified significant progressors with permutation analyses for each sector and globally. Significantly negative slopes fell in the tails below the 2.5% cutoff point. We compared the proportion of significant slopes between the devices with McNemar’s test.

Results : The mean (SD) baseline visual field mean deviation and mean (range) follow-up time were –8.2 (5.5) dB and 4.5 (2.2-6.7) years, respectively. The mean (SD) baseline global RNFL thickness was 61.4 (12.5) and 65.3 (10.0) μm for the Spectralis and Cirrus devices, respectively. The rates of RNFL change were significantly faster for Spectralis OCT compared to Cirrus OCT globally (–0.69; 95% CI: –0.90, –0.48 μm/year vs. –0.44; 95% CI: –0.71, –0.16 μm/year, p<0.001) and in most sectors (Figure 1). The proportion of significant negative slopes based on permutation analysis matched that of SLR, with a significantly higher proportion of progressing sectors in clock hours 3-6 and 8 for Spectralis OCT compared to Cirrus OCT, corresponding to the nasal, inferonasal, and inferotemporal regions (Table 1). The proportion of significant positive slopes was small and similar between the devices globally and for all sectors.

Conclusions : In this cohort of eyes with central or moderate to severe glaucoma, Spectralis OCT measurements tended to be faster and more likely to detect RNFL thinning over time compared to Cirrus OCT. OCT devices are not comparable with regard to detection of structural change in eyes with moderate to severe glaucoma damage.

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

 

Figure 1. Box plot demonstrates rates of RNFL change globally and at each clock hour sector as measured with Cirrus and Spectralis OCT devices.