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HUONG TRAN, Bo Wang, Ning-Jiun Jan, Gadi Wollstein, Matthew A Smith, Larry Kagemann, Hiroshi Ishikawa, Joel S Schuman, Elizabeth Tyler-Kabara, Ian A Sigal; In vivo Visualization of Posterior Lamina Cribrosa (LC) using SD-OCT Validated with Histology. Invest. Ophthalmol. Vis. Sci. 2014;55(13):913.
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© ARVO (1962-2015); The Authors (2016-present)
The LC plays a central role in the pathophysiology of glaucoma, and therefore its visualization has great potential to help understand the disease. Spectral domain (SD-) OCT has been demonstrated suitable to visualize the anterior surface of the LC in vivo, but the visibility of the posterior LC remains controversial. Our goal was to test the hypothesis that SD-OCT allows visualization of the posterior LC consistently across scans and eyes, and with sufficient quality to discern the microstructure of even the most posterior LC.
Eyes from two monkeys were cannulated and IOP was controlled using gravity perfusion. One eye from each monkey was scanned three times using OCT (Bioptigen, 3mm x 3mm, 512 x 512 pixels). Following this, both eyes were enucleated and perfusion fixed at an IOP of 30mmHg, 30 minutes post-death. They were then cryosectioned and imaged with a stereomicroscope (Nikon SMZ1500, 16bit greyscale, 0.765μm/pixel). The OCT-scanned eyes were sectioned coronally to verify the OCT-histology correspondence of LC microstructure. The non-OCT-scanned eyes were sectioned sagittally to evaluate the penetration depth of OCT signal. We delineated the visible posterior LC every 8th B-scan and computed the fraction of the scleral canal (defined by Bruch’s membrane opening - BMO). We performed the delineation in the three scans from each monkey, and the results compared to determine the repeatability of LC visibility.
Histology confirmed that the most posterior LC was visible in the OCT images (Figure). Qualitative comparison shows correspondence in LC microstructure between OCT and histology (Figure). Quantitative analysis shows comparable LC thickness: 335±4µm for OCT and 330±30µm for histology. Using BMO plane as a reference, the fraction of visible posterior LC was approximately 50% and was consistent within the three OCT scans from each monkey (Table).
SD-OCT allows visualization of the entire monkey LC thickness in vivo including the most posterior pores and beams. Posterior LC was consistently identified in approximately half of the area of the scleral canal defined by BMO. The extent to which our results apply to humans remains to be determined.
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