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MF Cordeiro, L Guo, T Morrissey, CS Sethi, PM Munro, DF Garway Heath, FW Fitzke; A Novel Method of Imaging the Rat Optic Nerve Head In Vivo With En-face Optical Coherence Tomography (OCT): Correlation With Confocal Microscopy . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2883.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: En-face optical coherence tomography (OCT) is a new high-resolution technique that can be used to image the optic nerve head (ONH). As the rat model is increasingly recognised as a useful tool for studying glaucoma, we have validated the results of en-face OCT imaging of rat ONH in vivo with confocal microscopy (CM) of the same eyes analysed post-mortem. Methods: 10 Brown Norway underwent general anaesthesia during which en-face OCT was used to image the fundus of each eye. Animals were killed soon after and enucleated eyes were fixed in paraformaldehyde and labeled with antibodies and special stains for axons, ganglion cell processes and extracellular matrix. 3D reconstructions of each rat ONH with CM were then compared to those obtained in vivo with en-face OCT. Results: Tomographic images of the ONH in each rat eye were reconstructed from multiple en-face OCT optical sections, as previously described. The images obtained were of high resolution showing clear detailed features of depth and topography. The mean posterior scleral thickness was OCT = 89 ± 10 microns, CM = 78 ± 12 microns. The z-profile of structures observed with en-face OCT were similar to those obtained with CM. Optical sections generated by OCT were 5 microns thick each, compared to CF which were 6.25 microns. Depth analysis of the different tissue planes and surface topography confirmed a similar relationship between the two methods of 3D reconstruction. Conclusion: The use of OCT tomographic imaging of the rat ONH in vivo to assess anatomical features of the ONH has been validated by our histological findings with CM. The difference in scleral thickness measurement may be due to tissue shrinkage post-mortem or differences in defining tissue borders with the two techniques. Obviously, en-face OCT is an advantageous method of imaging as it allows repeated in vivo measurements. Our results suggest that the high resolution of the OCT makes it a very useful tool for objectively measuring damage in ONH disease. More importantly, en-face OCT represents an exciting advance for monitoring changes in vivo at the ONH, particularly in longitudinal studies of the rat model of glaucoma. Acknowledgements: Adian Gh. Podoleanu, David A. Jackson.
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