Evaluation of the Temporal Anterior Chamber Depth Measured with Anterior Segment Swept-Source Optical Coherence Tomography and its Association with the Van-Herick Test and Angle Measurements

Abstract

Purpose : The aim of this study is to evaluate the Temporal Anterior Chamber Depth (TACD) measured with anterior segment Swept-Source Optical Coherence Tomography (SS-OCT) and its association with the Van Herick Test evaluated clinically and with the temporal and nasal angles measured with the anterior segment SS-OCT.

Methods : Subjects with glaucoma presenting typical ONH findings, high intraocular pressure with or without visual field (VF) damage and normal subjects were included. Patients underwent SS-OCT (DRI-Triton, Topcon) of the posterior and anterior segments. A 3mm length vertical B-scan of the peripheral temporal anterior chamber was obtained with the edges of the scan adjacent to the limbus (figure 1). The TACD was the average of 5 manual measurements of the depth 500 microns apart from the cornea to the iris using the caliper of the software of the SS-OCT (ImageNet 6, Topcon). Gonioscopy and a photograph of the slit lamp based Van Herick test (VHT) that evaluates the anterior chamber depth (0 to 100) were performed. The temporal angle and nasal angle were obtained with single 3mm length horizontal B-scans, and their measurements were also performed manually using the software of the device. Statistical analysis was performed using Linear Mixed Models Test and Pearson Correlation Coefficient.

Results : 32 eyes from 19 subjects were included. The mean (SD) age was 58.63±10.34. Mean (SD) circumpapillary RNFL (retinal nerve fiber layer) of the sample was 99.47 ±17.36 µm. The mean (SD) measurements were: TACD: 405.82±161.93 µm; Temporal Angle: 26.08±10.80 degrees; Nasal Angle: 25.47±11.33 degrees; VHT: 63.44±32.46. TACD was significantly associated with temporal angle (p<0.001); nasal angle (p<0.001) and VHT (p=0.001). TACD was also significantly correlated (p<0.001) with temporal angle (r=.737); nasal angle (r=.779) and VHT (r=.589).

Conclusions : TACD was significantly associated with the clinical evaluation of the VHT and with the measurements of the temporal and nasal angles. This parameter can be potentially useful as a novel biomarker for screening and evaluation of angle closure glaucoma using anterior segment SS-OCT.

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

 

Figures 1 and 2 depict horizontal B-scans of the temporal angle (A) with the corresponding vertical B-scan of the peripheral anterior chamber (B) used to measure TACD.