Understanding patterns of preserved central ganglion cells in advanced glaucoma using OCT

Abstract

Purpose : To better understand the patterns of preserved ganglion cell layer (GCL) in eyes with advanced glaucoma using optical coherence tomography (OCT).

Methods : The OCT GCL thickness was measured in 94 eyes (82 patients) with advanced glaucoma (AG_vf), defined as eyes with a 24-2 MD less than -12 dB. The MD ranged from -12.2 to –34.0 dB (mean of 18.2±4.93). A commercially available OCT analysis supplied the GCL thickness in 6 sectors of the thick, donut-shaped GCL region around the fovea. Fig. 1A shows the GCL thickness map of a healthy eye, and Fig. 1B shows the same map for a patient with AG_vf. For all eyes, the 6 sectors were coded as green (WNL, within-normal-limits), yellow (≤ 5^th percentile, but >1%), or red (≤1%) and shown as a pie chart (C). We represent the same information as a single bar, as illustrated in panel D for the GCL map in B with GCL thickness in μm.

Results : In all 94 eyes, one or more of the 6 sectors of the donut was abnormal (red or yellow), and all 6 sectors were red in 52 (55%) of the eyes. However, 33 eyes had at least one sector WNL (green). The pattern of damage varied widely across these 33 eyes as shown in Fig. 2A,B. Our working hypothesis, schematized in Fig. 2C, is that the ordering of preserved GCL reflects the natural history of progression independently within the superior (A) and inferior (B) hemiretinas. In particular, we assume that the damage proceeds from the temporal sector (TI or TS) to the middle sector (I or S), and finally to the most nasal sector (NI or NS). 61 of the 66 hemiretinas were consistent with this hypothesis (Fig. 2C); the 5 exceptions are indicated with the asterisks in Fig. 2A,B.

Conclusions : All the AG_vf eyes had damage to the critically important central, donut-shaped GCL region. However, the damage ranged from a single sector at ≤5% (yellow) with the other 5 sectors WNL (green), to over half of the eyes with all 6 sectors significantly thin (red, ≤1%). Furthermore, while there was a wide range of patterns of damage across eyes, these patterns were consistent with a hypothesized temporal to nasal progression of glaucoma in each hemi-donut. These results have implications for the clinical identification of macular progression, as well as criteria for inclusion in clinical trials seeking to preserve central macular function. 1. Hood et al., PRER, 2013. 2. Hood et al., PRER, 2017.

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