Estimation of foveal avascular zone area from a B-scan OCT image using machine learning algorithms

by Taku Toyama, Ichiro Maruko, Han Peng Zhou, Miki Ikeda, Taiji Hasegawa, Tomohiro Iida, Makoto Aihara, Takashi Ueta

Purpose

The objective of this study is to estimate the area of the Foveal Avascular Zone (FAZ) from B-scan OCT images using machine learning algorithms.

Methods

We developed machine learning models to predict the FAZ area from OCT B-scan images of eyes without retinal vascular diseases. The study involved three models: Model 1 predicted the FAZ length from B-scan images; Model 2 estimated the FAZ area from the predicted length using 1, 3, or 5 horizontal measurements; and Model 3 converted the FAZ area from pixels to mm². The models’ performance was evaluated using Mean Absolute Error (MAE), Mean Squared Error (MSE), and the Coefficient of Determination (R²). The FAZ area was subsequently estimated by sequentially applying Models 1→2→3 on a new dataset.

Results

Model 1 achieved a MAE of 2.86, MSE of 17.56, and R² of 0.87. Model 2’s performance improved with the number of horizontal measurements, with the best results obtained using 5 lines (MAE: 40.36, MSE: 3129.65, R²: 0.95). Model 3 achieved a MAE of 1.52e-3, MSE of 4.0e-6, and R² of 1.0. The accuracy of FAZ area estimation increased with the number of B-scan images used, with the correlation coefficient rising from 0.475 (1 line) to 0.596 (5 lines). Bland–Altman analysis showed improved agreement between predicted and actual FAZ areas with increasing B-scan images, evidenced by decreasing biases and narrower limits of agreement.

Conclusions

This study successfully developed machine learning models capable of predicting FAZ area from OCT B-scan images. These findings demonstrate the potential for using OCT images to predict OCTA data, particularly in populations where OCTA imaging is challenging, such as children and the elderly. Future studies could explore the developmental mechanisms of the FAZ and macula, providing new insights into retinal health across different age groups.