Fluorescein (lactone form) is a xanthene dye that is highly fluorescent, detectable even when present in minute quantities. Used forensically to detect traces of blood, in analytical chemistry as an indicator in silver nitrate titrations and in microscopy.

Application

Fluorescein sodium, the sodium salt of fluorescein, is used extensively as a diagnostic tool in the field of ophthalmology and optometry, where topical fluorescein is used in the diagnosis of corneal abrasions, corneal ulcers and herpetic corneal infections.