Identifying and understanding OCT artifacts (“red disease") that resemble arcuate damage due to glaucoma.

Abstract

Purpose : Arcuate-like artifacts seen on deviation/probability (p-) maps of healthy eyes are the most common source of OCT false positives and are the primary basis of so-called “red disease”. To better identify and understand these arcuate-like artifacts we tested a simple model.

Methods : The model: Figure 1A shows the average thickness map of healthy control (HC) eyes from a normative database. The black border, between the yellow and green regions in Fig.1A, is an iso-thickness (75 um) contour encompassing the thickest portion of the RNFL thickness map. Figure 1B&C show the thickness map and p-map of a healthy control with an arcuate-like artifact. Notice that the RNFL thickness (Fig. 1C) of this HC eye is relatively normal, but that the thickest portion no longer falls entirely within the black border. The model predicts that the arcuate-like artifact is due to this misalignment, and it will fall largely within the black contour (red arrow, Fig. 1B). However, arcuate regions that are due to glaucoma will typically extend outside these black borders, and often cross the midline (black vertical line) as shown in Fig. 1D-F. The model was tested by superimposing the black borders on the p-maps of 200 HC eyes. In addition, these borders were also superimposed on the RNFL p-maps of 62 glaucoma eyes with early (EG, MD>-6dB, n=32), moderate (MG, MD<-6dB, >-12dB, n=12), and advanced disease (AG, MD <-12 dB, n=18).

Results : Arcuate-like artifacts were seen on the RNFL p-maps of 8 (4%) of the 200 HC eyes. As predicted, all 8 (100%) of these arcuate artifacts fell within the black borders as shown in Fig. 2A (1^st column). On the other hand, only 3 of the 62 patient eyes (2 EG and 1 MG) had abnormal regions restricted to within the black border (Fig. 2B). A post-hoc analysis revealed that these 3 eyes can be distinguished from the 8 HC eyes based upon topographical agreement with the abnormal regions of the RNFL thickness map and/or ganglion cell layer (GCL) p-map, as shown in the 2^nd and 3^rd columns of Figs. 2A&B.

Conclusions : Arcuate-like artifacts on RNFL p-maps, which can be confused with glaucomatous arcuate damage, fall within the borders of the thick arcuate region of the average RNFL thickness map of healthy eyes. Abnormal arcuate regions falling within these borders should be assumed to be artifacts unless confirmed with GCL p-maps and/or RNFL thickness maps.

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