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Saman Kiumehr, Sung Chul Park, Syril Dorairaj, Christopher C. Teng, Celso Tello, Jeffrey M. Liebmann, Robert Ritch; Spatial Consistency between Focal Lamina Cribrosa Defects, Retinal Nerve Fiber Layer Loss and Glaucomatous Visual Field Deficits. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3066.
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To assess focal defects of the lamina cribrosa (LC) in glaucoma using enhanced depth imaging spectral-domain optical coherence tomography (EDI SD-OCT) and their spatial relationship to visual field (VF) and retinal nerve fiber layer (RNFL) loss.
Serial horizontal and vertical B-scan images (interval between images: approximately 30 µm) of the optic nerve head were obtained using EDI SD-OCT for both eyes of normal and glaucoma subjects. Focal defects, which were defined as localized LC deformation in one 45-degree sector of the optic disc, were sought and evaluated for their patterns. Structure-function relationships were assessed using a 6-sector VF map, and spatial consistency was determined using RNFL thickness profiles.
A total of 31 normal and 57 glaucoma subjects were included. Twelve focal defects of the LC were found in 9 glaucoma eyes, versus none in the normal eyes. Six eyes had a partial-thickness LC defect with a moth-eaten appearance (Fig A) or a full-thickness hole (Fig B). Six eyes had partial (Fig C) or complete (Fig D) disruption of the LC insertion. Three eyes had both patterns, which occurred in the same 45-degree topographic sector. All 12 focal defects occurred in the periphery of the inferotemporal quadrant. Two defects (Fig B,D) appeared clinically as an acquired pit of the optic nerve (APON) and the other 10 defects as notches or increased cupping of optic disc. All focal LC defects corresponded to the VF sector with the greatest mean loss of sensitivity in the pattern deviation numeric plot and to the region with the RNFL defect.
Mechanisms of LC deformation in glaucoma include focal melting/collapse of laminar beams and focal disruption of the LC insertion, both of which may cause a clinical APON in extreme cases. Focal LC defects occur in tandem with localized RNFL and VF defects.
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