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nicholas tan, Yih Chung Tham, Sri Gowtham Thakku, Baskaran Mani, Tin Aung, Michael J A Girard, Ching-Yu Cheng; The Lamina Cribrosa Global Shape Index and Its Application in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5532. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
As the morphology of the lamina cribrosa (LC) is altered in glaucoma, structural LC-specific parameters on imaging such as LC-depth or LC-curvature have been reported; however, these 1- or 2-dimensional (D) measures poorly reflect the 3D complexity of the LC. Our aim was therefore to examine if a LC global shape index (LC-GSI) was related to the presence or severity of glaucoma.
We included total of 176 subjects (mean age 62.9 ± 8.1 years), comprising of 76 healthy controls and 99 subjects with primary open angle glaucoma (POAG), into a observational, cross-sectional study. Optical coherence tomography (OCT) scans of the optic nerve head (ONH) were obtained from all subjects. Enhanced depth imaging and adaptive compensation were used to better visualise and delineate the anterior surface of the LC. We then reconstructed the ONH in 3D, and calculated the LC-GSI, a metric that quantitatively describes the overall geometrical shape of the anterior LC surface (more negative LC-GSI values correspond to greater cupping of the LC). Anterior LC depth and 2D-curvature were also measured. Severity of glaucoma was defined by the extent of visual field loss, based on the Hodapp-Parrish-Anderson grading. Linear regression analyses compared LC characteristics between controls, mild-moderate, and advanced POAG groups.
After adjusting for age, gender, ethnicity, intraocular pressure, axial length and corneal curvature, the LC-GSI was most negative in the advanced POAG group (mean [standard error] =-0.34 [0.05]), followed by the mild-moderate POAG group (-0.31 [0.02]) and then controls (-0.23 [0.02], PTrend=0.01). There was also a significant trend of increasing LC depth and greater LC horizontal curvature with increasing severity of glaucoma (PTrend=0.04 and 0.02, respectively).
With more severe glaucoma, the LC-GSI was increasingly more negative, and the anterior LC depth and curvature greater. These observations collectively correspond to greater cupping of the ONH at the level of the LC. As the LC-GSI describes the 3D anterior LC morphology, its potential usage may be complementary to existing pre-laminar ONH parameters that are commonly measured and reported on OCT imaging.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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