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SEUNG HYEN LEE, Tae-Woo Kim, Eun Ji Lee, Kyoung Min Lee; Comparison of Depth and Curvature of the Lamania Cribrosa as a Biomarker for Optic Nerve Head Strain. Invest. Ophthalmol. Vis. Sci. 2016;57(12):831.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior bowing of the lamina cribrosa (LC) has been considered as a primary pathogenic event in glaucoma. Since the emergence of spectral domain-optical coherence tomography (OCT), LC depth from the Bruch’s membrane opening (BMO) level has been used as a parameter to measure the magnitude of posterior displacement of the LC. However, such LC depth measurement is limited in that it is affected by the choroidal thickness which is known to largely vary among individuals. LC curvature is another parameter that can be conceived as an index of LC strain.
Fifty two eyes of 52 patients with primary open angle glaucoma (POAG) and 52 eyes of 52 healthy control subjects who were matched for age, gender, and intraocular pressure (IOP) were included. The LC depth from the BMO and LC curvature index (LCCI) were measured in horizontal B-scan images obtained using swept-source (SS)-OCT at seven equidistant locations.
The mean IOP in healthy subjects and POAG group were 13.8 and 14.3 mmHg, respectively (P=0.304). The mean LC depth (427.0±88.5 vs.511.6±90.9 μm, P<0.001) and LCCI (6.94±1.11 vs.10.39±2.58, P<0.001) were significantly larger in POAG group than healthy subjects. The upper 95 percentile values of mean LC depth and LCCI in healthy subjects were 565.4 μm and 9.28, respectively. Fifteen POAG patients (28.9%) and 32 POAG patients (61.5%) had LC depth and LCCI greater than the upper 95 percentile value of healthy subjects, respectively. Higher IOP and younger age were associated with greater LCCI (all P≤0.009) in POAG.
Although both LC depth and LCCI were larger in POAG patients than in healthy subjects, there was a large overlap in the distribution of LC depth between POAG and healthy subjects. In contrast, small overlap was found in LCCIs between two groups. This finding suggests that LC curvature is a better biomarker of optic nerve head strain than LC depth.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
(A) Measurement of the LCCI which was defined as (width/depth)x100. The LC depth (green arrows) from the BMO (white dotted line) is larger in the healthy eye (B) while the LC is posteriorly curved (red dots) only in the glaucomatous eye (C). Note that the peripapillary choroid is much thicker in the healthy eye. The comparison of these two cases indicates that LC depth measured from the BMO can improperly represent the LC strain due to individual variation of the choroidal thickness.
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