Quantification of optic nerve head structure using optical coherence tomography in dogs with glaucoma and retinal degeneration

Abstract

Purpose : There is no established topography of the canine optic nerve head (ONH) by spectral-domain optical coherence tomography (SD-OCT) in normal and disease conditions. This study was conducted to investigate the ONH structure using the SD-OCT in dogs with primary angle closure glaucoma (PACG) and retinal degeneration (RD).

Methods : Near-infrared reflection and cross-sectional B-scan images of ONH and peripapillary retinal nerve fiber layer were obtained with SD-OCT (Spectralis, Heidelberg Engineering) from 15 dogs with PACG (n=5; 7.8 ± 1.9 yr, 23.6 ± 6.8 kg), RD (n=5; 7.3 ± 1.3 yr, 18.5 ± 7.7 kg), or normal fundic morphology (n=5; 6.8 ± 1.5 yr, 21.6 ± 8.7 kg). The following ONH parameters were measured using ImageJ: cup-to-disc ratio (CDR), cup volume (CV), maximum cup depth (MCD), lamina cribrosa displacement (LCD), and Bruch’s membrane opening (BMO). One-way ANOVA followed by Tukey’s multiple comparison test (GraphPad Prism) was used for statistical analysis.

Results : Two castrated-male and 13 spayed-female dogs were included in this study and there were no significant differences in age (P = 0.679) or body weight (P = 0.664) between groups. The CDR was significantly higher in PACG (0.92 ± 0.05) compared with normal fundic morphology (0.31 ± 0.07; P < 0.001) and RD (0.33 ± 0.07; P < 0.001). The PACG revealed significantly increased CV (1.77 ± 0.91 mm²), MCD (876.1 ± 216.0 µm), and LCD (805.3 ± 211.4 µm) compared with normal fundic morphology (0.11 ± 0.03 mm²; P = 0.001, 212.8 ± 21.2 µm; P < 0.001 and 30.7 ± 41.2 µm; P < 0.001, respectively) and RD (0.31± 0.11 mm²; P = 0.002, 355.4 ± 156.6 µm; P = 0.001 and 133.2 ± 101.6 µm; P < 0.001, respectively). However, BMO did not significantly differ between dogs affected by PACG (2095 ± 285.3 µm), RD (2157 ± 264.8 µm; P = 0.928), or normal fundic morphology (2296 ± 250.8 µm; P = 0.482). Dogs with RD did not demonstrate significant differences in the 5 measurements from dogs with normal fundic morphology (BMO, P = 0.699; CV, P = 0.818; MCD, P = 0.344; LCD, P = 0.488; CRD, P = 0.852).

Conclusions : Objective evaluation of the canine ONH using SD-OCT showed that PACG increased the volume and depth of the optic cup as well as higher CDR compared with normal and RD. Further studies are warranted for longitudinal changes of canine ONH in PACG and RD.

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