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Z. Hu, M. D. Abramoff, Y. H. Kwon, K. Lee, M. K. Garvin; Circularity Comparison of the Clinical Optic Disc and Automatically Segmented Neural Canal Opening in SD-OCT Images. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4361.
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The neural canal opening (NCO), visible in 3-D SD-OCT, is a promising stable reference structure for monitoring glaucomatous progression. The purpose of this study is to investigate the hypothesis that the NCO segmented in SD-OCT tends to be more "circular" or "round" than the disc margin delineated on the stereo fundus photographs. This may be the case particularly in those eyes in which the optic nerves appear "tilted."
68 SD-OCT volumes centered at the optic nerve head (ONH) of 34 patients with glaucoma were obtained from CirrusTM HD-OCT. The corresponding fundus photographs (Nidek 3Dx) were also obtained. Four intraretinal surfaces were segmented in the original raw OCT images and the OCT images were flattened based on the surface segmentation. From each flattened image, the NCO was automatically segmented using a graph-theoretic approach. Manual planimetry was performed by glaucoma experts to delineate a reference standard (RS) for the disc margins on the fundus images. The circularity ratio or isoperimetric quotient was used to evaluate the circularity of the NCO and optic disc. The 68 scans were divided into two groups, i.e., the more circular group and the less circular group based on the average of the optic disc circularity ratio of the RS. The area correlations of the NCO and optic disc were computed. The relationship of the circularity ratio and area correlation was investigated.
The investigation demonstrates that the NCO in SD-OCT images is significantly more circular than the optic disc on fundus images. The more circular group has greater area correlation between NCO and optic disc than the less circular group.
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