Fluorescein Dye Concentration as a Factor in Tear Film Fluorescence

Abstract

A large variation in the degree of fluorescence is observed clinically when using fluorescein dye for the evaluation of the ocular surface. Although this variation may not be so important in the case of diagnosing an epithelial defect, such as in a corneal or conjunctival abrasion, it becomes very important when attempting to evaluate the ocular surface in the presence of various degrees of corneal defects that occur in dry eye syndromes. For example, clinically there may be a high degree of variation in fluorescence when using paper impregnated with fluorescein (fluorescein strips) to introduce dye onto the ocular surface, in contrast to the more consistent observations using fluorescein liquid dye, though the appearance is also dependent upon the concentration and volume instilled onto the eye. The degree of fluorescence observed on the ocular surface appears to be concentration dependent, and light of a longer wavelength is emitted with increasing fluorescein concentration.¹ We have observed that increasing the concentration of fluorescein dye to 10% results in nearly 100% quenching of fluorescence for the first few minutes after instillation. Quenching is related to the fluorescein concentration on the ocular surface.² The purpose of this study was to evaluate this fluorescein quenching phenomenon in normal eyes and its relationship to the tear film.