Noninvasive Raman spectroscopic identification of intraocular lens material in the living human eye

Purpose: To develop a safe noninvasive technique for identifying the materi al of intraocular lenses (IOLs) implanted in patients. Setting: Center for Biomedical Engineering and the Department of Ophthalmol ogy and Visual Sciences, University of Texas Medical Branch, Galveston, Tex as, USA. Methods: Raman spectroscopy was used to noninvasively identify the type of IOL implanted after previous cataract surgery in 9 eyes of 6 patie nts who were legally blind as a result of eye disease. Three IOLs were char acterized: poly(methyl methacrylate) (PMMA) (n = 5), acrylic (n = 3), and s ilicone (n = 1). Confocal Raman spectroscopy was used with a laser power of 95 muW and exposure time of 1 second. Results: Distinct spectral peaks associated with each type of IOL were obta ined. These included spectra peaks at 2840 cm(-1), 2946 cm(-1), and 3000 cm (-1) for PMMA; 2917 cm(-1), 2939 cm(-1), and 3055 cm(-1) for acrylic; and 2 900 cm-1, 2961 cm(-1), and 3048 cm(-1) for silicone. The procedure was well accepted by patients, and there were no complications. Conclusions: The specific Raman spectra of the IOLs allowed for noninvasive determination of IOL material with the use of a safe light dose and an exp osure time of 1 second.