Focal lamina cribrosa defects associated with glaucomatous rim thinning and acquired pits

Importance: Considering the potential clinical importance of focal lamina cribrosa (LC) defects as a characteristic structural feature in glaucoma and a risk factor for glaucomatous visual field progression, it may be helpful to know the structure of focal LC defects and the spatial relationship between them and glaucomatous optic disc changes such as neuroretinal rim thinning/notching and acquired pits of the optic nerve (APON). Objective: To investigate structural and spatial relationships between focal LC defects and glaucomatous neuroretinal rim thinning/notching and APON. Design: In a cross-sectional analysis of data from an ongoing, prospective, longitudinal study, serial enhanceddepth imaging (EDI) optical coherence tomographic (OCT) images of the optic nerve head were obtained from patients with glaucoma and reviewed for focal LC defects (laminar holes or disinsertions). Anterior laminar insertion points and edges of laminar holes or disinsertions were marked in EDI-OCT images, reconstructed 3-dimensionally, and superimposed on optic disc photographs. Setting: A glaucoma referral practice. Participants: Two hundred thirty-nine eyes (120 patients) were examined. Fifty-four eyes were excluded because of an incomplete horizontal or vertical set of serial EDI-OCT images or poor-quality EDI-OCT images owing to media opacity, irregular tear film, or poor patient cooperation. Among the remaining 185 eyes, 40 (from 31 patients) had laminar holes or disinsertions and were included for analysis. Main Outcome Measures: Presence, extent, and location of laminar holes or disinsertions. Results: Among 185 eyes, 11 laminar holes and 36 laminar disinsertions were found in 40 eyes. Superimposed images of the 3-dimensionally reconstructed focal LC defects and disc photographs showed that the outline of the LC defect corresponded almost precisely to that of clinical APON for 6 laminar holes and that the LC defect was much larger than and enclosed APON for 10 laminar disinsertions. The remaining 5 laminar holes and 26 laminar disinsertions corresponded to focal neuroretinal rim loss, with no evidence of APON in disc photographs. Conclusions and Relevance: Focal LC defects (laminar holes or disinsertions) are associated with neuroretinal rim loss and APON. The extent of LC defects can be visualized more effectively on EDI-OCT images than by clinical examination.