Optical fibre coupled ocular spectrometer for measurement of drug concentration in the anterior eye-applications in pharmaceuticals research

This paper describes in detail a novel optoelectronic system designed to measure drug absorption in the anterior segment of the eye following topical application of drug formulations. This minimally invasive measurement technique offers both a method for determining drug concentration in human eyes, and demonstrates an alternative to current testing processes in model animals, which require paracentesis of the anterior chamber of the eye. The optoelectronic technique can be used with formulations, which possess appropriate spectral characteristics, namely unique absorption or fluorescence spectra. Preliminary experiments using our measurement system have been performed in rabbit and man, where we have been successful in achieving the direct measurement of topically applied brimonidine, an alpha-2 agonist used in the treatment of glaucoma. This demonstrates the feasibility of performing real-time, in vivo testing of ophthalmic drug formulations in the eye of human test subjects. We further demonstrate the novel application of the optoelectronic system for detection of topically applied UV-absorbing compounds in rabbit cadaver eyes, with a view to evaluating potential ocular sunscreen formulations. In summary, this method can be applied for the rapid comparison of the penetration of different drug formulations into the anterior eye at greatly reduced cost and time