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L. T. Dudek, S. Chalfin, R. D. Glickman; Oblique Incidence Reflectometry (OIR): Building an Instrument Suited for Sampling the Ocular Surface. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5013.
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© ARVO (1962-2015); The Authors (2016-present)
Biopsy of ocular surface lesions is problematic given the small volume of tissue available, sampling error and scarring. Currently, there are no clinically available non-invasive techniques for detecting malignancy in suspicious ocular surface lesions. Previous work by Chalfin et al. (IOVS, 41(ARVO Suppl):S787, 2000) indicates ocular surface lesion backscatter spectroscopy produces unique signatures when compared to a control site of the patient’s own conjunctiva using a 2-channel spectral analyzer from a single sampling probe in parallel with 6 illumination fibers. Mehrubeoglu et al. (App Optics, Vol 41:182, 2002), tested a probe, measuring 35 mm across at its tip, designed for skin lesions. They suggested that sampling the backscatter from tissue from multiple collection fibers organized in an array produces data more specific and sensitive than from a single sampling fiber. Furthermore, Marquez, et al. (App Optics, Vol 37:798, 1998) has shown that signatures change when the illumination is directed from an oblique angle.
We adapted a small, prefabricated eight-channel fiber optic array probe with two illumination fibers for the purpose of ocular surface sampling. A dual conductor 105 micron fiber optic cable was constructed with SMA termination, to fit into a quartz-tungsten-halogen lamp source. One of the bare illumination fibers was mounted onto one side of the prefabricated probe in parallel with the sampling fibers. The other was mounted at a 30 degree angle from the axis of the probe fibers. The bare fibers were secured and cast into epoxy then polished using standard fiber polishing technique. Modified plastic pipettes were used to house the assembly.
OIR signatures were collected with the assembled probe. A Spectralon® reflectance standard was used to correct for spectral characteristics of the lamp. Optical signatures were captured with an eight-channel, imaging spectrometer CCD array, and the resulting data stored on a personal computer for later analysis.
We demonstrate that a miniaturized probe for OIR can be constructed for ocular sampling to allow more precise optical characterization with this multi-channel technique. We anticipate developing a normative database to correlate OIR signatures with normal ocular surface tissue, benign and malignant lesions.
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