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Citation: Thakku SG, Tham Y-C, Baskaran M, et al. A global shape index to characterize anterior lamina cribrosa morphology and its determinants in healthy Indian eyes. Invest Ophthalmol Vis Sci. 2015;56:3604-3614. DOI:10.1167/iovs.15-16707 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 À1 to þ1. 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 ¼ 0.020), smaller vertical cup-to-disc ratio (VCDR) (P ¼ 0.007), and larger minimum rim width (BMO-MRW) (P ¼ 0.001). A deeper LC was associated with male sex (P < 0.001), shorter axial length (P ¼ 0.003), larger VCDR (P < 0.001), and smaller BMO-MRW (P ¼ 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.Keywords: lamina cribrosa morphology, optic nerve head, optical coherence tomography A major site of retinal ganglion cell (RGC) damage in glaucoma is at the optic nerve head (ONH), where RGC axons congregate before making their way to the brain. [1][2][3] Within the ONH, RGC axons pass through a mesh-like collagen fiber structure called the lamina cribrosa (LC), before exiting the eye.Lamina cribrosa morphology and progression of glaucoma are believed to be closely related. 4 In particular, glaucomatous onset is associated with posterior displacement of the anterior LC surface, 5-7 posterior migration of the LC insertion points, 6 and backward bowing of the entire LC. 8 Nonhuman primate models of glaucoma have also shown similar associations. 9-11Furthermore, these models suggest that LC changes precede surface level retinal nerve fiber layer (RNFL) thinning, 11,12 which is a useful marker of glaucoma onset. Taken together, these findings indicate that an assessment of LC morphology may potentially be used as a biomarker for early glaucoma detection. The...

Citation: Tun TA, Thakku SG, Png O, et al. Shape changes of the anterior lamina cribrosa in normal, ocular hypertensive, and glaucomatous eyes following acute intraocular pressure elevation. Invest Ophthalmol Vis Sci. 2016;57:4869-4877. DOI:10.1167/ iovs.16-19753 PURPOSE. The purpose of this study was to estimate and compare changes in anterior lamina cribrosa (LC) morphology in normal, ocular hypertensive (OHT), and glaucomatous eyes following acute elevations in intraocular pressure (IOP). METHODS. The optic nerve heads (ONHs) of 97 subjects (17 OHT, 19 primary open-angle glaucoma [POAG], 31 primary angle-closure glaucoma [PACG], and 30 normal subjects) were imaged using optical coherence tomography (OCT). Intraocular pressure was raised twice by applying forces to the anterior sclera, using an ophthalmodynamometer. After each IOP elevation, IOP was held constant and measured; each ONH was rescanned with OCT. In each OCT volume, the anterior LC was enhanced, delineated, and its global shape index (GSI) calculated and compared across groups.RESULTS. The baseline IOP was 17.5 6 3.5 mm Hg and was increased to 38 6 5.9 mm Hg and then to 46.5 6 5.9 mm Hg. At the first IOP increment, mean GSI was significantly smaller than that at baseline in normal subjects and glaucoma subjects (P < 0.05) but not in OHT subjects (P ¼ 0.12). For the second IOP increment, the mean GSI was significantly smaller than that at baseline in normal subjects and in OHT eyes (P < 0.05). After adjusting for age, sex, and baseline IOP, the LC of POAG eyes was found to be significantly more posteriorly curved than that of normal subjects (P ¼ 0.04).CONCLUSIONS. Acute IOP elevations altered anterior LC shape in a complex nonlinear fashion. The LC of POAG eyes was more cupped following acute IOP elevations compared to that of normal subjects.