Abstract
Purpose :
The 200x200 Optic Disc Cube is a scan used to measure thickness of the retinal nerve fiber layer (RNFL) as well as cup-to-disc ratio (C/D). The RNFL and the C/D are affected in glaucoma and result in peripheral vision loss. Using thicknesses of the RNFL and the C/D compared to a normative database allows a clinician to diagnose glaucoma and monitor it accordingly. The CIRRUS™ 6000 (ZEISS, Dublin, CA) has a camera capture rate that is 100 kHz compared to the 27 kHz of the CIRRUS HD-OCT 5000 (ZEISS, Dublin, CA). The CIRRUS 6000 scans 30% faster and thereby reduces artifacts such as blink and dryness. The purpose of this study is to compare the RNFL and C/D measurements between the CIRRUS 6000 and CIRRUS 5000.
Methods :
The 200x200 Optic Disc Cube was obtained using both the CIRRUS HD-OCT 5000 and 6000 on 20 normal patients (mean: 40 years SD:15 years). The retinal nerve fiber layer surrounding the optic nerve is divided into 12 sections or 4 quadrants. The C/D is determined by the rim area to disc area. The RNFL thicknesses and C/D were compared between the devices using linear regression and Bland-Altman plots.
Results :
The linear regression for RNFL thickness and C/D showed a very strong relationship between the CIRRUS 5000 and CIRRUS 6000 (R2= 0.94 and 0.99 respectively) shown in Figure 1. Bland-Altman plots show good agreement between the two devices with an average mean difference of 0.45 microns for RNFL and 0.01 for C/D ratio (Figure 2). Paired T-tests show that the differences are not statistically significant between the two devices (p=0.42 and 0.15 respectively).
Conclusions :
The CIRRUS 6000 can use the same normative database as the 5000 to identify abnormal RNFL thickness and C/D ratio which is specifically important in glaucoma diagnosis. Since glaucoma is a disease of change, clinicians can continue to track the same patients as they had before with earlier CIRRUS models (CIRRUS 5000 and 4000), and take advantage of the faster speed of the CIRRUS 6000.
This is a 2020 ARVO Annual Meeting abstract.