Lamina Cribrosa Steepness Index to Measure the Morphology of the Lamina Cribrosa in Myopic Eyes With Optic Disc Distortion

Abstract

Purpose: To propose a new parameter for evaluating lamina cribrosa (LC) morphology in myopic eyes with optic nerve head (ONH) distortion. Methods: This study included 169 eyes with normal-tension glaucoma (NTG) and myopic ONH distortion from the Myopic NTG Treatment Study. The LC curvature index (LCCI) and the LC steepness index (LCSI) were assessed in optical coherence tomography B-scan images obtained using an enhanced-depth imaging technique. These were measured as the curvature of the anterior LC surface within Bruch's membrane opening and as the slant of the temporal anterior LC surface relative to the plane of the anterior scleral opening, respectively. Results: The LCSI was strongly correlated with the LCCI (R2 = 0.594, P < 0.001). A larger LCSI was associated with a thinner LC (P = 0.021) and narrower peripapillary γ-zone (P < 0.001). Neither the LCCI nor the LCSI was associated with the severity of visual field (VF) damage. A thinner LC (P = 0.009), and thinner retinal nerve fiber layer (P < 0.001) were significantly associated with worse VF mean deviation. Conclusions: The strong correlation between the LCCI and LCSI indicates that the latter may substitute the former for evaluating LC morphology in myopic eyes where ONH distortion blocks the visibility of the whole LC. Translational Relevance: The LCSI may serve as a reliable biomarker for assessing LC deformation in myopic eyes with optic nerve head distortion, enhancing evaluations when visibility is limited.