Apparatus for Quantitative Slit-Lamp Ocular Fluorometry

摘要

Ocular Fluorometry has long been used to measure the presence and concentration of tracers in ocular tissues and fluids and, more and more, quantification of natural occurring fluorescence. Early detection of abnormalities in Diabetic Retinopathy has been a major field of application of this non-invasive technique. A slit-lamp based Ocular Fluorometer has been developed (US patent 06,013,034) based on a multi-element sensor to quantify fluorescence along line segments of ocular globe by electronic scanning. In this paper we describe a new version of the Ocular Fluorometer hardware and present results on the assessment of its performance. Increased flexibility is offered due to the possibility of using different kinds of sensors and cameras. Portability is also improved as USB/RS232 communications are used for data and command flow between computer and Data Acquisition System. Finally measurement performance also improved significantly: Lower Level of Detection (LLOD) down to 1.5 ng/ml fluorescein equivalent concentration has been reached using conventional NMOS multielement image sensors and preliminary results indicate that 0.1 ng/ml can be reached with a cooled CCD camera. The 16-bit Analog-to-Digital converter used and the low-noise amplification allow full use of sensors wide dynamic range, linearity and resolution. Corneal fluorescence measurements are presented as preliminary in vivo low-light-level quantification results.