The goal of this project is to develop a general-purpose instrument for measuring fluorescence lifetimes on and inside the eye. This instrument will take advantage of fluorescence lifetime probes designed for microscopy and analytical chemistry to measure cell volume, oxygen, concentration of electrolytes, pH, and other variables of importance in and on live eyes in animals and eventually humans. This will have obvious applications in eye research and may eventually have applications in disease diagnosis and monitoring. This instrument will also be useful in the measurement of endogenous fluorescence. Thus, autofluorescence of cornea and lens are elevated in diabetes while fluorescent retinal lipofuscins are implicated in the pathogenesis of Age Relate Macular Degeneration. During Phase I, we demonstrated feasibility of this technique in the eye. We have developed a particularly sensitive method for measurement fluorescence lifetimes that is uniquely suited for ocular applications. The eye poses challenges of limited entrance aperture, potential movement, and limited tolerance to light exposure both in terms of intensity and duration. Our overall goal will be to produce a standardized instrument and to develop protocols for making fluorescent lifetime measurements using endogenous or exogenous fluorescent molecules in or on the eye. A critical goal will be standardization and calibration control, so that results made on different machines are comparable. In addition, we will design this instrument with enough flexibility so that we can add capabilities as new fluorescence lifetime probes are developed, and our customers can develop techniques of their own.