A Study Validating the Estimation of Anterior Chamber Depth and Iridocorneal Angle with Portable and Non-Portable Slit-Lamp Microscopy

Abstract

This study assessed the anterior chamber depth (ACD) and iridocorneal angle using a portable smart eye camera (SEC) compared to the conventional slit-lamp microscope and anterior-segment optical coherence tomography (AS-OCT). This retrospective case-control study included 170 eyes from 85 Japanese patients. The correlation between the ACD evaluations conducted with the SEC and conventional slit-lamp was high (r = 0.814). The correlation between the Van-Herick Plus grade obtained using two devices was also high (r = 0.919). A high kappa value was observed for the Van-Herick Plus grading (Kappa = 0.757). A moderate correlation was observed between the ACD measured using AS-OCT and the slit-lamp image acquired with the conventional slit-lamp microscope and SEC (r = 0.609 and 0.641). A strong correlation was observed between the trabecular-iris angle (TIA) measured using AS-OCT and Van-Herick Plus grade obtained with the conventional slit-lamp microscope and SEC (r = 0.702 and 0.764). Strong correlations of ACD evaluation and high kappa value of the Van-Herick Plus grading indicated the adequate subjective assessment function of the SEC. Moderate correlations between the ACD objective measurement and evaluation and strong correlation between the TIA and Van-Herick Plus grade suggested the good objective assessment function of the SEC. The SEC demonstrated adequate performance for ACD evaluation and angle estimation.

Keywords: anterior chamber depth; anterior-segment optical coherence tomography; slit-lamp microscope; smart eye camera; trabecular-iris angle.

Figure 1

Photographs of the conventional slit-lamp microscope and the smart eye camera (SEC). (A) Appearance of the conventional slit-lamp microscope (700GL; Takagi, Nagano, Japan). External camera is installed inside (THD-23FHD; IKEGAMI TSUSHINKI CO., LTD., Tokyo, Japan). (B) Appearance of the smart eye camera (OUI Inc., Tokyo Japan). The attachment includes a thin slit and a cylinder lens to converts the light source from the smartphone into a 1-mm thin beam.

Figure 2

Scan of the analysis interface in anterior-segment optical coherence tomography (AS-OCT) (CASIA2 Advance system: Tomey, Nagoya, Japan). (A,B) Anterior chamber depth (ACD) was define the distance between the apex of the posterior corneal to apex of the crystalline lens using AS-OCT. (C) Trabecular-iris angle (TIA) was measured with the apex in the iris angle recess and the arms of the angle passing through a point on the trabecular meshwork 500 μm from the SS and the point on the iris.

Figure 3

Case presentation. (A) Ophthalmological images of a 62-year-old Asian man. The upper-tier images were obtained using the smart eye camera (AC: shallow/shallow, Van-Herick Plus grade: 3/3). The middle-tier images were obtained using conventional slit-lamp microscopy (AC shallow/shallow, Van-Herick Plus grade: 3/3). The bottom-tier images were obtained using AS-OCT (ACD: 2.481/2.484 mm, TIA: 21.3/20.4°). (B) Ophthalmological images of a 32-year-old Asian woman. The upper-tier images were obtained using the smart eye camera (AC: deep/deep, Van-Herick Plus grade: 4/4). The middle-tier images were obtained using the conventional slit-lamp (AC deep/deep, Van-Herick Plus grade: 4/4). The bottom-tier images were obtained using AS-OCT (ACD: 3.415/3.388 mm, TIA: 66.7/61.9°). AS-OCT: anterior-segment optical coherence tomography, ACD: anterior chamber depth, TIA: trabecular-iris angle.