The effect of viscosity of the vehicle on the penetration of fluorescein into the human eye

Abstract

Comparisons were made of the penetration of fluorescein into the aqueous humour of normal human subjects from eye drops made up with saline or with viscous polymers—methylcellulose and two grades of polyvinyl alcohol. Two of these materials produced a small increase in penetration which was independent of their concentration. After instillation of the same drops into the eye, the decline of fluorescence of the tear film was followed. Viscous drops gave a slightly higher fluorescence at all times but otherwise no prolongation of contact time. The increase in penetration was considered to result from a greater initial saturation of the tear film in the case of the viscous drop, or possibly a direct effect on the corneal permeability.