A Global Shape Index to Characterize Anterior Lamina Cribrosa Morphology and Its Determinants in Healthy Indian Eyes.

ABSTRACT

PURPOSE: Lamina cribrosa (LC) morphology could be implicated in the progression of glaucoma. To date, no established, quantifiable parameter to assess LC shape in vivo exists. We aim to introduce a new global shape index for the anterior LC (LC-GSI) and to identify associations with ocular factors in a healthy Indian population. METHODS: Optical coherence tomography (OCT) scans of the optic nerve head (ONH) were performed on 162 healthy subjects. Optic nerve head structures were delineated and a geometric characterization of anterior LC morphology was obtained by measuring curvature along 180 LC cross sections and representing it as LC-GSI ranging from -1 to +1. Lamina cribrosa depth and curvature were also reported. Linear regression was used to identify factors associated with LC morphology. RESULTS: The typical healthy LC had a saddle rut-like appearance, with a central ridge visible in superior-inferior cross sections. A more prominent central ridge (larger LC-GSI) was associated with shorter axial length (P < 0.001), smaller Bruch's membrane opening (BMO) area (P = 0.020), smaller vertical cup-to-disc ratio (VCDR) (P = 0.007), and larger minimum rim width (BMO-MRW) (P = 0.001). A deeper LC was associated with male sex (P < 0.001), shorter axial length (P = 0.003), larger VCDR (P < 0.001), and smaller BMO-MRW (P = 0.002). Age and IOP were not significantly associated with LC morphology in healthy eyes. CONCLUSIONS: The LC-GSI is a single index that quantifies overall LC shape in an intuitive way. Ocular determinants of LC-GSI in healthy eyes included risk factors for glaucoma (axial length, VCDR, and BMO-MRW), highlighting the potential role of LC morphological characterization in the diagnosis and monitoring of glaucoma.