In Vivo Evaluation of Focal Lamina Cribrosa Defects in Glaucoma

Objectives: To assess focal lamina cribrosa (LC) defects in glaucoma using enhanced depth imaging optical coherence tomography and to investigate their spatial relationships with neuroretinal rim and visual field loss. Methods: Serial horizontal and vertical enhanced depth imaging optical coherence tomographic images of the optic nerve head were obtained from healthy subjects and those with glaucoma. Focal LC defects defined as anterior laminar surface irregularity (diameter, >100 mu m; depth, >30 mu m) that violates the normal smooth curvilinear contour were investigated regarding their configurations and locations. Spatial consistency was evaluated among focal LC defects, neuroretinal rim thinning/notching, and visual field defects. Results: Forty-six healthy subjects (92 eyes) and 31 subjects with glaucoma (45 eyes) were included. Ninety-eight focal LC defects representing various patterns and severity of laminar tissue loss were found in 34 eyes with glaucoma vs none in the healthy eyes. Seven of 11 eyes with glaucoma with no visible focal LC defect had a deeply excavated optic disc with poor LC visibility. Eleven focal LC defects presented clinically as an acquired pit of the optic nerve, and the others as neuroretinal rim thinning/notching. Focal LC defects preferably occurred in the inferior/inferotemporal far periphery of the LC including its insertion. Eyes with focal LC defects limited to the inferior half of the optic disc had greater sensitivity loss in the superior visual hemifield and vice versa. Conclusions: Mechanisms of LC deformation in glaucoma include focal loss of laminar beams, which may cause an acquired pit of the optic nerve in extreme cases. Focal LC defects occur in tandem with neuroretinal rim and visual field loss.