Abstract
Purpose :
To test a model of progression of glaucomatous damage in the central macula.
Methods :
The model: At the optic disc, retinal nerve fiber layer (RNFL) damage appears first in the temporal half of the superior and inferior quadrants, shown as the red superior and inferior vulnerability zones (SVZ & IVZ respectively) in Fig. 1A,B.[1] Given RNFL disc anatomy,[1,2] early IVZ damage can affect the perifoveal macular region (±8°, thin black circle, Fig. 1B), including the TI and I sectors of the donut-shaped region of dense ganglion cells (GC). Early SVZ damage does not affect this GC region.[2] Progression into the temporal quadrant (TQ, green arc) of the disc is depicted by the regions in blue, green, and yellow, and the red arrows. As RNFL damage moves further into the TQ of the disc, damage to the GC donut proceeds from TS to S to NS sectors, and from TI to I to NI (Fig. 1E). Test data: Optical coherence tomography (OCT) cube scans, centered on the fovea, were obtained from 62 eyes with glaucoma;[3] 32 eyes had 24-2 MD better than -6dB, while 30 had MD values between -6dB and -24.7dB. Commercial software divided the donut region into 6 sectors; see the GC thickness map in Fig. 1C. These sectors were color coded as red (≤1%), yellow (>1%, ≤5%) or green (>95%) (Fig. 1D), based upon GC layer thickness. In addition, the first and last scans of 10 eyes previously designated “definite progression” (DP) [4] were examined.
Results :
As predicted, 1. TI was the most affected sector and was significantly thinned in 82% of the 62 eyes. 2. For both hemi-donuts (upper, lower), the temporal sectors (TS, TI) had the greatest number (44, 51) of abnormal (red or yellow) eyes, followed by the middle sectors (37, 44), and then the nasal sectors (31, 38). 3. 89% of the 124 hemi-donuts showed a pattern predicted by the model. 4. For 9 of the 10 DP, including the eye in Fig. 2, the model predicted the pattern of change from first to last test (left column, t1 & t2, and orange arrow) and the expansion of damage into the TQ of the disc (Fig. 2, right column, orange arrows).
Conclusions :
The model described the progression of damage into the central macula, which is the region critical for functions such as driving and reading. This has implications for detecting progression in the clinic, as well as in clinical trials. 1. Hood et al. PRER, 2017; 2. Hood et al. PRER, 2013; 3. Hood et al. PRER, 2022; 4. Hood et al., Ophthal Glau, 2022.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.