Uveal outflow is segmental

Abstract

Purpose : Previous studies have demonstrated that conventional outflow is segmental but the pattern in unconventional (or uveal) outflow remains unknown. This study investigated the flow pattern along the uveal outflow pathway and its correlation with conventional outflow.

Methods : Male C57BL/6J mice (10 weeks old, n=4) were stabilized under anesthesia. To label the outflow pattern, 1 µl fluorescent microspheres were injected into the anterior chamber. After 45 minutes, all injected eyes were fixed in situ with 4% paraformaldehyde (PFA) for 30 minutes. After euthanizing, the eyes were enucleated and further fixed in 4% PFA at 4^oC for 48 hours. The eyes were dissected into 12 wedges based on clock hours. Images of both sides of each wedge were captured by confocal microscope after nuclear staining and analyzed. For each eye, the superior and nasal sides were placed at 12 and 3 o’clock respectively. The flow patterns were analyzed using ImageJ, ZEN, and GraphPad Prism. Statistical analysis was performed by Kruskal-Wallis test and Spearman correlation.

Results : Segmental outflow patterns were observed in both the ciliary body (CB) and suprachoroidal space (SCS) of the uveal outflow pathway. The tracer intensity was highest in the temporal quadrants and lowest in the superior quadrants in the uveal outflow. The highest tracer intensity in CB was at 8 o’clock which was significantly higher than that at 12 o’clock by 88 ± 3% (p<0.01). In SCS, the tracer intensity and length were highest and longest at 10 o’clock and both were significantly higher than those at 1 o’clock by 92 ± 4% (p<0.05) and 91 ± 6% (p<0.05) respectively. A significantly positive correlation was found between the tracer intensity in CB and SCS (r= 0.71; p<0.05) but no correlation was found between the uveal and conventional outflow pathway (p>0.05). Four different patterns of outflow were observed: 1. only conventional; 2. only uveal; 3. both uveal and conventional; 4. non-/ low- flow in both uveal and conventional outflow.

Conclusions : We found a segmental flow pattern in both CB and SCS regions of the uveal outflow pathway in mouse eyes. There was no correlation between conventional and uveal outflow. Understanding the segmental pattern of uveal outflow will lead to a better location for the placement of drainage devices and drug delivery.

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

 

Four outflow patterns: 1. only conventional; 2. only uveal; 3. both uveal and conventional; 4. non-/ low- flow in both uveal and conventional outflow.