Limiting factors to the OCT axial resolution?for in-vivo imaging of human and rodent retina in the 1060nm wavelength range

A computational model was developed to evaluate the limitations to the highest axial resolution, achievable with ultrahigh resolution optical coherence tomography (UHROCT) in the 1060nm wavelength region for in-vivo imaging of the human and rodent retina. The model considers parameters such as the wavelength dependent water absorption, the average length of the human and rodent eyes, and the power limitations for the imaging beam as defined in the ANSI standard. A custom-built light source with re-shaped spectrum was used to verify experimentally the results from the computational model. Axial OCT resolution of 4.2µm and 7.7µm was measured from a mirror reflection with the custom light source by propagating the imaging beam through water cells with 5mm and 25mm thickness, corresponding to the average axial length of the rodent and human eye respectively. Assuming an average refractive index of 1.38 for retinal tissue, the expected axial OCT resolution in the rodent and human retina is 3µm and 5.7µm respectively. Retinal tomograms acquired in-vivo from the rat eye with the modified light source show clear visualization of all intraretinal layers, as well as a network of capillaries (~10µm in diameter) in the inner- and outer plexiform layers of the retina. ©2009 Optical Society of America

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