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Asymmetry between right and left fundus images identified using convolutional neural networks
Tae Seen Kang1, Bum Jun Kim1, Ki Yup Nam2
1Department of Ophthalmology, Gyeongsang National University Changwon Hospital, #11 Samjeongja-ro, Seongsan-gu, Changwon, 51472, Republic of Korea.
Scientific Reports
|January 28, 2022
Summary
Convolutional neural networks (CNNs) can accurately distinguish between right and left fundus images, identifying the macula as a key feature. However, data augmentation using image flipping may introduce bias in machine learning models.
Area of Science:
- Ophthalmology
- Computer Vision
- Medical Imaging
Background:
- Fundus image analysis is crucial for diagnosing ocular diseases.
- Distinguishing between right and left eye images is essential for accurate AI-driven diagnostics.
- Previous studies often use image flipping for data augmentation, potentially introducing bias.
Purpose of the Study:
- To evaluate the capability of convolutional neural networks (CNNs) in discriminating between right and left fundus images.
- To identify discriminative regions within fundus images utilized by CNNs.
- To assess the impact of data augmentation techniques on CNN performance.
Main Methods:
- Trained multiple CNN architectures (DenseNet121, ResNet50, VGG19) on a large dataset of fundus images (98,038 images).
- Utilized the Ocular Disease Intelligent Recognition dataset for augmentation.
- Employed class activation mapping to visualize discriminative image regions.
Main Results:
- CNNs achieved high accuracy (>99.3% and >91.1%) in differentiating right and left fundus images.
- Model accuracy varied with CNN architecture depth and complexity.
- Class activation mapping pinpointed the macula as the primary discriminative region.
- DenseNet121 showed no significant discrimination for left-eye-only images (55.1%).
Conclusions:
- CNNs are highly effective in distinguishing lateral eye images from fundus photographs.
- The macula is a critical anatomical landmark for lateral eye discrimination by CNNs.
- Caution is advised when using horizontal flipping for data augmentation in fundus image datasets to prevent bias.

