The ocular permeability of two sieved fractions of prednisolone acetat
e with a mean particle size of < 5-mu-m and 5-10-mu-m was studied in r
abbits. The results show that there was not significant difference bet
ween the corneal uptake of the two fractions of prednisolone acetate.
Prednisolone acetate was rapidly taken up by the cornea where it is hy
drolyzed rapidly to prednisolone. Only prednisolone was detected in th
e aqueous humor showing that prednisolone acetate is completely hydrol
yzed in the cornea. Both fractions produced similar concentrations of
prednisolone in the aqueous humor. For prednisolone acetate, the perme
ability rate rather than the dissolution rate seems to be the rate-lim
iting step for corneal transport.