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N. G. Strouthidis, H. Yang, B. Fortune, I. A. Sigal, C. F. Burgoyne; Visualization of the Anterior Laminar Cribrosa Surface (ALCS) in Normal and Experimental Glaucoma (EG) Eyes Using Spectral Domain Optical Coherence Tomography (SD-OCT). Invest. Ophthalmol. Vis. Sci. 2010;51(13):3857.
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To characterize the extent and reproducibility of SD-OCT ALCS visualization within both eyes of 9 longitudinally imaged rhesus macaques with unilateral laser induced EG.
9 rhesus macaques underwent baseline and post-laser optic nerve head (ONH) imaging (Heidelberg Spectralis; 870 nm center wavelength; 15º, 80 radial B-scan pattern) in both eyes under isoflurane anesthesia with IOP manometrically stabilized at 10 mmHg. Two baseline (pre-laser) and two follow-up (post-laser) volumes were analyzed. The first follow-up was at the onset of HRT-detected surface height depression and the second was the most recent, or pre-sacrifice, acquisition. Using custom software, four masked operators delineated the ALCS and the neural canal opening (NCO) in alternate B-scans (40/volume). To identify the extent and reproducibility of delineated ALCS within each ONH, each delineated ALCS point was projected to the NCO reference plane. NCO area was divided into 100 equal sized regions and the number of regions with two or more ALCS points in all 4 volumes was assessed.
‘Shared’ ALCS delineation points (present in all four volumes) for both eyes of all 9 animals at the second follow-up are shown in the figure. While the extent of ‘missing’ areas is variable between animals, in most eyes they directly correspond to the location of the central retinal vasculature. No systematic effect of time was found for either the percentage of LC marks retained (p = 0.52, repeated measures ANOVA) or the percentage area retained (p = 0.65), suggesting that the area of ALCS marked was reliable over time in both control and EG eyes. The average area marked was 66.6% in control eyes and 66.2% in EG eyes.
Relatively large areas of the ALCS were detected and reproducibly delineated in longitudinal SD-OCT (870 nm) images of the ONH in both control and glaucomatous eyes. A formal comparison of ALCS visualization using 870 and 1060 nm center wavelength SD-OCT imaging will commence shortly.
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