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Conrad Merkle, Danielle J. Harper, Martin Glösmann, Gerhard Garhofer, Bernhard Baumann; Melanin identification using spectroscopic OCT and clinical feasibility evaluation. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2519.
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Melanin content in the retina can be identified non-invasively by polarization-sensitive optical coherence tomography (PS-OCT), however few clinical OCT systems have the hardware required to perform this analysis. Here, we propose to use traditional OCT at the clinical 840 nm wavelength range to obtain similar identification of melanin content through spectroscopic analysis to make this biomarker available to more clinical systems.
In this study, a custom PS-OCT ophthalmoscope for rodent retinal imaging was used to acquire PS-OCT and traditional OCT data simultaneously. Retinal data was acquired from a very-low-density lipoprotein receptor (VLDLR) mouse model using a traditional volumetric angiogram scan profile with 5 B-scan repeats at each slow-axis position. The VLDLR model presents with substantial retinal lesions and migration of melanin into the inner retina. Spectroscopic processing split the OCT spectrum into 20 channels across an 85 nm band from 803 to 888 nm (Figure 1). Clinical feasibility testing used the central 10 channels for a narrower 40 nm bandwidth from 825 to 865 nm. A spectroscopic filter was developed to highlight positive spectral slopes associated with melanin and was compared against PS-OCT and traditional OCT in the VLDLR model.
Images of melanin using the spectral filter method produced similar features to those obtained from PS-OCT including melanin migration and disruption of layers containing melanin in the VLDLR model. It was noted that the spectral filter was in general noisier than the PS-OCT signal and presented artefactual signals below large vessels. While the spectral filter images were further noisier using the 40 nm clinical bandwidth rather than the full 85 nm bandwidth, key features could still be distinguished. Intensity images were not able to specifically distinguish the above features.
The presented spectral filter for melanin identification was able to show similar information to PS-OCT. While the spectral filter did not provide as robust of a signal as PS-OCT, it did not require PS-OCT hardware, which few clinical OCT systems possess. For this reason, this spectroscopic approach may allow more rapid enhancement of clinical OCT by using existing clinical systems with spectroscopic post-processing.
This is a 2021 ARVO Annual Meeting abstract.
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