A new objective slit-lamp fluorophotometer was developed to examine corneal epithelial barrier function. This instrument has several new characteristics. The photodetector system is placed directly in front of the cornea and the focal diamond is accurately positioned at the corneal surface, permitting measurement of the barrier function of peripheral parts of the cornea. Due to the filter characteristics, measurement can be done even in a relatively bright room. Only one second is needed for measurement, eliminating blink interruption. Linear relationships were found between measurement count and fluorescein concentration. 0.5% and 3 microliters of fluorescein was applied to the eyes of healthy volunteers. In non-washed eyes, the concentration changes were consistent with tear turnover, and in washed eyes, the changes reflected the barrier function of the corneal epithelium and showed correlation with age. This instrument is also useful for determining autofluorescence. A significant relation was seen between autofluorescence and age.