Comparison of Foundation and Supervised Learning-Based Models for Detection of Referable Glaucoma from Fundus Photographs
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Purpose
To compare the performance of a foundation model and a supervised learning-based model for detecting referable glaucoma from fundus photographs.
Design
Evaluation of diagnostic technology.
Participants
6,116 participants from the Los Angeles County Department of Health Services Teleretinal Screening Program.
Methods
Fundus photographs were labeled for referable glaucoma (cup-to-disc ratio ≥ 0.6) by certified optometrists. Four deep learning models were trained on cropped and uncropped images (Training N = 8,996; Validation N = 3,002) using two architectures: a vision transformer with self-supervised pretraining on fundus photographs (RETFound) and a convolutional neural network (VGG-19). Models were evaluated on a held-out test set (N = 1,000) labeled by glaucoma specialists and an external test set (N = 300) from University of Southern California clinics. Performance was assessed while varying training set size and stratifying by demographic factors. xRAI was used for saliency mapping.
Main Outcome Measures
Area under the receiver operating characteristic curve (AUC-ROC) and threshold-specific metrics.
Results
The cropped image VGG-19 model achieved the highest AUC-ROC (0.924 [0.907-0.940]), which was comparable ( p = 0.07) to the cropped image RETFound model (0.911 [0.892-0.930]), which achieved the highest Youden-optimal performance (sensitivity 82.6%, specificity 88.2%) and F1 score (0.801). Cropped image models outperformed their uncropped counterparts within each architecture ( p < 0.001 for AUC-ROC comparisons). RETFound models had a performance advantage when trained on smaller datasets (N < 2000 images), and the uncropped image RETFound model performed best on external data ( p < 0.001 for AUC-ROC comparisons). The cropped image RETFound model performed consistently across ethnic groups ( p = 0.20), while the others did not ( p < 0.04); performance did not vary by age or gender. Saliency maps for both architectures consistently included the optic nerve.
Conclusion
While both RETFound and VGG-19 models performed well for classification of referable glaucoma, foundation models may be preferable when training data is limited and when domain shift is expected. Training models using images cropped to the region of the optic nerve improves performance regardless of architecture but may reduce model generalizability.
