Is fluorescein stain hydrophilic or hydrophobic?

Fluorescein stain is classified as hydrophilic, which means it has an affinity for water and can dissolve in aqueous solutions. This characteristic is crucial in veterinary ophthalmology, where fluorescein is commonly used to assess the integrity of the corneal epithelium. When fluorescein stain is applied to the surface of the eye, it readily adheres to moist tissues and penetrates damaged areas of the cornea, making it an effective tool for identifying corneal abrasions or ulcers.

Understanding the hydrophilic nature of fluorescein helps practitioners recognize why it spreads easily on the eye's surface and why it can provide vital diagnostic information. In contrast, hydrophobic compounds would not interact well with the tear film or corneal surface, limiting their usefulness in such applications. Additionally, while terms like oleophobic or biphasic can describe other substances, they do not apply to fluorescein's behavior in ocular diagnostics.