A LIGHTWEIGHT COMPACT CONVOLUTIONAL TRANSFORMER FOR TYMPANIC MEMBRANE CLASSIFICATION IN OTOSCOPY IMAGING

The accurate assessment of tympanic membrane (TM) conditions—such as effusion, normal membrane appearance, or the presence of ventilation tubes—is essential for timely diagnosis and treatment of otitis media (OM), one of the leading causes of preventable hearing loss in children. However, visual otoscopic examination remains highly subjective, and diagnostic accuracy varies widely across clinicians due to inconsistent image quality, limited training, and subtle variations in membrane morphology. Recent deep learning–based approaches have shown strong performance, yet most rely on large-scale pretraining or heavyweight convolutional networks that are impractical for point-of-care deployment. Vision Transformers (ViTs) have emerged as powerful feature extractors, but their reliance on fixed patch tokenization and a global class token results in large parameter counts and suboptimal performance on small medical datasets. In this study, we propose a lightweight Compact Convolutional Transformer (CCT) for TM image classification trained from scratch on a clinical otoscopy dataset. Unlike standard ViT architectures, CCT integrates convolutional tokenization to extract local visual patterns before self-attention, and sequence pooling replaces the class token, reducing model complexity while preserving global reasoning. We conduct a structured ablation study varying both convolutional kernel size (3×3, 5×5, 7×7) and transformer encoder depth (3, 5, 7 layers), resulting in nine model configurations. Across these experiments, the optimal configuration (7×7 kernel, 3 transformer layers) achieved 91.21% accuracy and 90.65% macro F1 on the test set with only 3.26M parameters, outperforming deeper models and demonstrating superior efficiency–performance trade-offs. Results show that wider convolutional tokenizers effectively capture broader visual patterns of the TM, while excessive transformer depth may introduce overfitting on small datasets. These findings indicate that compact transformer architectures can deliver high diagnostic performance without transfer learning or large data requirements, supporting their potential for real-time clinical decision support and integration into low-resource or mobile otoscopy systems.