Glaucoma Expert-Level Detection of Angle Closure in Goniophotographs With Convolutional Neural Networks: The Chinese American Eye Study

Abstract

Purpose: To compare the performance of a novel convolutional neural network (CNN) classifier and human graders in detecting angle closure in EyeCam (Clarity Medical Systems, Pleasanton, California, USA) goniophotographs.

Design: Retrospective cross-sectional study.

Methods: Subjects from the Chinese American Eye Study underwent EyeCam goniophotography in 4 angle quadrants. A CNN classifier based on the ResNet-50 architecture was trained to detect angle closure, defined as inability to visualize the pigmented trabecular meshwork, using reference labels by a single experienced glaucoma specialist. The performance of the CNN classifier was assessed using an independent test dataset and reference labels by the single glaucoma specialist or a panel of 3 glaucoma specialists. This performance was compared to that of 9 human graders with a range of clinical experience. Outcome measures included area under the receiver operating characteristic curve (AUC) metrics and Cohen kappa coefficients in the binary classification of open or closed angle.

Results: The CNN classifier was developed using 29,706 open and 2,929 closed angle images. The independent test dataset was composed of 600 open and 400 closed angle images. The CNN classifier achieved excellent performance based on single-grader (AUC = 0.969) and consensus (AUC = 0.952) labels. The agreement between the CNN classifier and consensus labels (κ = 0.746) surpassed that of all non-reference human graders (κ = 0.578-0.702). Human grader agreement with consensus labels improved with clinical experience (P = 0.03).

Conclusion: A CNN classifier can effectively detect angle closure in goniophotographs with performance comparable to that of an experienced glaucoma specialist. This provides an automated method to support remote detection of patients at risk for primary angle closure glaucoma.

Keywords: Angle closure; artificial intelligence; goniophotography; gonioscopy; primary angle closure glaucoma.

Figure 1:

Representative EyeCam images of a closed (top) and open (bottom) angle.

Figure 2:

ROC curve with 95% confidence interval (grey bar) of CNN classifier performance in detecting angle closure in the test dataset based on labels by the reference glaucoma specialist. Performance of human graders shown with years of clinical experience in parentheses.

Figure 3:

ROC curve with 95% confidence interval (grey bar) of CNN classifier performance in detecting angle closure in the test dataset based on labels by the panel of glaucoma specialists. Performance of human graders shown with years of clinical experience in parentheses.

Figure 4:

Representative class activation maps of the final layer of the CNN indicating the most salient (red and yellow) regions of the images. Representative images of open (top) and closed (bottom) angles.