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A. Unterhuber, B. Povazay, B. Hermann, H. Sattmann, A. Chavez–Pirson, W. Drexler; Optical Coherence Tomography at 1040nm – Enhanced Visualization of the Choroid . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3507.
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in vivo retinal imaging using optical coherence tomography (OCT) employing 1040 nm light for significantly improved visualization of the choroid
Time–domain and frequency–domain OCT technology using light centered at 1040 nm has been developed for high speed ultrahigh resolution retinal imaging for the first time. Commonly OCT systems for retinal imaging use spectral wavelengths below 930 nm, because of water absorption. Utilizing a light source with a spectrum centred at 1040 nm within the first absorption window has the advantages to significantly reduce OCT signal losses due to absorption and scattering at the melanin rich retinal pigment epithelium (RPE) and deeper layers, therefore enabling significantly deeper penetration into the underlying choriocapillaris and choroid. Furthermore light at 1040 nm is less scattered hence less attenuated by turbid media (e.g. corneal haze and cataract) that often occur in elderly eyes with retinal pathologies, commonly limiting applicability of OCT.
High speed (up to 15000 A–scans per second) and high resolution (< 5 µm axial resolution) OCT imaging enabled volumetric visualization of not only the retina with all major intraretinal layers, but also superficial (∼ 200 µm) regions of the choroid as compared to retinal OCT imaging at 800 nm. Unprecedented three–dimensional representation of the RPE/choriocapillaris/choroid interface as well as chroidal vessels and their branching could be accomplished using OCT at 1040 nm wavelength.
Retinal OCT at longer wavelengths significantly improves the visualization of the retinal pigment epithelium/choriocapillaris/choroid interface and superficial choroidal layers as well as reduces the scattering through turbid media and therefore might provide a better diagnosis tool for early stages of retinal pathologies such as age related macular degeneration which is accompanied by choroidal neovascularization, i.e. extensive growth of new blood vessels in the choroid and retina.
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