Identification of intraocular lens materials using confocal Raman spectroscopy

Purpose: To develop and test a noninvasive method to identify intraocular lens (IOL) materials in vitro. Setting: Center for Biomedical Engineering and the Department of Ophthalmology University of Texas Medical Branch, Galveston, Texas, USA. Methods: A laser confocal Raman spectroscopy system (Conforam) was used for the noninvasive assessment of Raman spectra in the lower and the higher spectral regions (299.1 to 1833.7 cm^-1 and 2633.8 to 3819.6 cm^-1, respectively) of 4 IOL materials: silicone, poly(methyl methacrylate) (PMMA), acrylic, and hydrogel. Results: Each lens material showed a distinctive spectrum in both the higher and the lower spectral regions. Most materials had unique peaks and a distinct profile using 1 mW of laser power and a 1 second exposure time. All materials still had a unique spectrum n both the higher and the lower region that allowed 1 material to be distinguished from the others. Conclusions: A Conforam differentiated silicone, PMMA, acrylic, and hydrogel lenses in vitro. Raman spectroscopy using the Conforam may provide a fast, safe, and reliable noninvasive method to gain information about the material of an implanted IOL and the stability of lens materials and their coatings.