Dynamic Accommodative Stress Testing for Early Detection of Anterior Segment Deformation Patterns in Subclinical Keratoconus

This prospective diagnostic accuracy study (n=180) investigated dynamic anterior segment alterations during accommodative stress (0D, 3D, 6D) in subclinical keratoconus (SKC) eyes compared to VAE-NT and healthy controls using combined Scheimpflug-Placido imaging and AS-OCT. SKC eyes demonstrated significantly exaggerated anterior segment deformation with mean ΔACD of -0.114±0.021 mm and ΔKmax of 1.78±0.28 D at 6D accommodation versus controls (-0.068±0.015 mm and 0.68±0.18 D; p<0.001). The proposed Dynamic Ectasia Index (DEI = √(ΔKmax × |ΔACD| × 10)) achieved 96.7% sensitivity and 95.0% specificity (AUC 0.982), significantly outperforming the static Belin/Ambrósio D-index (AUC 0.892). The bivariate model combining DEI and Corneal Thickness Redistribution Index (CTRI = inferotemporal thinning + superonasal thickening) achieved the highest diagnostic accuracy with 98.3% sensitivity and 96.7% specificity (AUC 0.993). Accommodative stress testing reveals characteristic deformation patterns in SKC eyes not apparent on static imaging, providing a functional framework for early ectasia detection, though external validation is required before clinical implementation.