Optical coherence tomography (OCT) is a standard for retinal imaging and has been integrated to surgical microscopes to evaluate tissue-instrument interactions during macular surgery. One common procedure during such surgery, membrane peeling, is done under a white light microscope. Indocyanine green (ICG) can be used to specifically dye the inner limiting membrane (ILM) and facilitates this surgery. However, there is no equivalent contrast mechanism to specifically target the ILM on OCT images. We propose to use photothermal OCT (PT-OCT) to detect ICG in the OCT field-of-view, which would increase contrast between the ILM and other structures of the retina. As preliminary data for this project, we have collected PT-OCT images of different ICG phantoms over a wide range of laser powers and ICG concentrations, including concentrations lower than the clinical standard. We have also detected a PT-OCT signal from ICG on a mouse tail with low photothermal laser powers (0.56 mW) to evaluate the feasibility of this technique for in vivo ocular imaging. Finally, we have collected PT-OCT images of a fixed monkey retina after the ILM was dyed with ICG, and obtained a PT-OCT signal from the ICG and the melanin present in the retinal pigment epithelium and the choroid. Those preliminary results indicate that ICG can be detected with PT-OCT at low concentrations and low laser powers. PT-OCT has never been demonstrated in the human eye and has only been recently demonstrated in the mouse eye. This experiment establishes feasibility for PT-OCT in clinical applications.
Maryse Lapierre-Landry, Joseph Carroll, Michael T. Nork, Yuankai K. Tao, and Melissa C Skala, "Photothermal optical coherence tomography of indocyanine green in the eye (Conference Presentation)," Proc. SPIE 10474, Ophthalmic Technologies XXVIII, 1047410 (Presented at SPIE BiOS: January 28, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2290296.5751469740001.
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