Optical Coherence Tomography-Derived Excavation Index and Structure-Function Damage in Glaucoma

Area of Science:

• Ophthalmology
• Medical Imaging
• Glaucoma Research

Background:

• Glaucomatous optic neuropathy involves progressive lamina cribrosa (LC) deformation, leading to optic disc (OD) excavation and visual field (VF) loss.
• Quantifying OD excavation is crucial for diagnosing and monitoring glaucoma progression.

Purpose of the Study:

• To introduce and validate the Excavation Index (EI), a new optical coherence tomography (OCT)-based parameter for quantifying OD excavation.
• To assess the EI's association with structural and functional glaucoma metrics.

Main Methods:

• 107 eyes (23 controls, 84 primary open-angle glaucoma) underwent OCT and VF testing.
• EI was calculated as the ratio of excavation width to peripheral LC depth (EI=Ew/PLCD×100).
• Correlations with LC curvature index (LCCI), retinal nerve fiber layer (RNFL) thickness, and VF indices were analyzed.

Main Results:

• EI values increased significantly with glaucoma severity (P<0.001).
• EI strongly correlated with RNFL thickness (r=-0.749), MD (r=-0.696), PSD (r=0.570), VFI (r=-0.701), and LCCI (r=0.710) (all P<0.001).
• Multivariate analysis identified intraocular pressure, RNFL thickness, and LCCI as independent predictors of EI. ROC analysis showed EI's AUC (0.860) was comparable to LCCI (0.864).

Conclusions:

• The EI reliably measures glaucomatous OD excavation.
• EI demonstrates potential as a complementary biomarker for glaucoma staging and monitoring.
• The EI shows promise for detecting early-stage glaucoma due to its sensitivity to structural changes.