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L Guo, FW Fitzke, T Morrissey, DJ Keegan, DF Garway Heath, MF Cordeiro; Comparison of in vivo En-face Optical Coherence (OCT)and Scanning Laser (SLO) Tomography of Optic Nerve Head in the Rat . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4032.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The rat model is increasingly recognised as a useful tool for studying glaucoma. However, an effective objective technique of assessing the rat optic nerve head (ONH) in vivo is yet to be established. We compare two possible imaging methods that may allow longitudinal assessment of rat models of glaucomatous disease. Methods: 15 Brown Norway and Lister-hooded rats underwent general anaesthesia following which a Zeiss prototype scanning laser ophthalmoscope (SLO) and a new en-face optical coherence tomograph (OCT) were used to image both fundi. Animals were killed soon after following which enucleated eyes were analysed histologically. Characteristics of the two imaging techniques including 3D tomographic reconstructions were compared. Results: The depth resolution of the en-face OCT was measured to be approximately 20-30 microns compared to the SLO which was found to be 200 - 300 microns. Tomographic images of the ONH in each rat eye were reconstructed from 24 SLO optical sections generated using confocal optics, as we have previously described. These were compared to en-face OCT tomographic images of the same eyes which were reconstructed from 140 optical sections. The 3D images obtained from the en-face OCT were of much greater resolution, allowing better discrimination of tissue planes and appreciation of ONH topography in all eyes studied. En-face OCT compared to SLO allowed area and volume measurements of the ONH to be made with greater precision. In addition 3D confocal histological reconstruction correlated more closely with OCT rather than SLO tomography. Conclusion: Our results suggest that en-face OCT tomographic imaging of the rat ONH in vivo is superior to SLO. Both methods of imaging allow repeated in vivo measurements. The increased resolution of the en-face OCT however appears to make it a more useful tool than SLO in defining the degree of optic nerve head disease. We suggest that this new method of en-face OCT tomography is an important advance in in vivo ONH imaging and has great potential in the study and investigation of the rat model of glaucoma. Acknowledgements: Adian Gh. Podoleanu, David A. Jackson.
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