Corneal quantitative fluorometry - A slit-lamp based platform

Abstract

Ocular Fluorometry has long been used (since early eighties) to measure non-invasively the presence and concentration of tracers in ocular tissues and fluids. The most common tracer has been sodium fluorescein, after systemic administration, but tissue native fluorescence has also been clinically valuable. Our goal is the development of a cooled CCD-camera based instrument configured as an accessory to a slit-lamp - a common instrument in ophthalmic observation of anterior eye - capable of measuring fluorescence in the eye from cornea to anterior vitreous with enough sensitivity and spatial resolution. Sensitivity of 0.1 ng/ml fluorescein equivalent concentration and 100 μm axial spatial resolution have been achieved with in vitro tests. This represent a crucial step forward in slitlamp based quantitative measurements as several new clinical issues can be addressed: Cornea auto-fluorescence and its relation with Diabetic Retinopathy and corneal function evaluation are two of them. With those figures of sensitivity and spatial resolution one can use narrower excitation bands in different wavelengths to address different fluorophores and also reduce slit widths and optimize angular positioning in order to reach inner locations in the eye with enough axial resolution. Accurate corneal in vivo fluorescence quantification evaluating its relation with age and pathologies like diabetes is our first step. Some results have already been achieved and are presented. These developments will also make it possible to improve quantification of Blood-Aqueous Barrier (BAB) leakage into anterior chamber and to assess anterior vitreous fluorescence resulting from Blood-Retinal Barrier (BRB) breakdown. Both are closely related with Diabetes progression. © 2010 International Federation for Medical and Biological Engineering.