Abstract
Purpose :
The current speculation suggests that vascular abnormalities contribute to the development of neurodegenerative diseases and glaucoma. This study explored the temporal and regional changes in vascular density and neurodegeneration in a controlled monkey model, aiming to understand whether vascular abnormalities are linked to the development of neurodegeneration in glaucoma.
Methods :
High ocular pressure was induced in unilateral eye of cynomolgus monkeys by performing repeatedly laser photocoagulation of trabecular meshwork. The intraocular pressure (IOP) was followed by using Icare TONOVET tonometer. The vessel density of radial peripapillary capillary (RPC, between ILM-NFL) and retinal nerve fiber layer thickness (RNFLt) was measured before the photocoagulation and after laser-induction. Changes of vessel density and RNFLt were analyzed in 4 regions of the peripapillary area, i.e. superior, inferior, nasal and temporal quadrants. Statistical analysis was conducted using IBM SPSS for correlations (Spearman test) and non-parametric tests (Wilcoxon test).
Results :
1. Thirteen monkeys with IOP reaching 45-55 mmHg within 5 months were included in the analysis. The average IOP was 18.54 ± 0.62 mmHg before laser photocoagulation, 31.31 ± 4.18 (1-3M after photocoagulation), 45.23 ± 3.32 (4M), 46.54 ± 3.53 (5M) and 46.38 ± 3.56 (6 M).
2. Peripapillary RNFLt thinning was first observed in the superior and inferior quadrants, showing correlation with IOP (p < 0.001), consistent with patient data. Decline in peripapillary vessel density was also noted in the superior and inferior regions, and as well as nasal region .
3. Peripapillary vessel density decline was first detected at 4M, preceding the notable RNFLt decrease at 5M, indicating that vascular changes appeared earlier than retinal nerve fiber atrophy in a monkey glaucoma model.
Conclusions :
The study findings indicated that decline of vessel density during the initial months of heightened IOP showed greater time and quadrant sensitivity compared to the thinning of RNFLt in a glaucoma monkey model. This suggests that earlier onset of vascular changes plays a crucial role in the development of neurodegeneration in glaucoma.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.