Introduction The intraocular penetration of penicillin was studied by investigators1,2 about 20 years ago. Since that time a variety of different types of penicillin have been discovered and used for clinical and experimental purposes. In addition, a biosynthetic penicillin phenoxymethyl penicillin (Penicillin V) became available in 1955. Ampicillin* or P-50 (6-[D(—)-α-Aminophenyl-acetamido]penicillanic Acid) is a new semisynthetic penicillin, with a wider bacterial spectrum of activity than other penicillins. This penicillin largely overcomes the disadvantage of not being absorbed after oral administration. No serious toxic effects have been encountered experimentally when the drug was administered either orally or subcutaneously in doses of 5 g/kg and intravenously in doses of 2.5 g/kg.3 Minimal inhibitory concentration of this antibiotic was determined to be 0.01-0.05μg/ ml for common Gram-positive organisms, 0.1μg/ml to 0.5μg/ml for Hemophilus influenzae, and 0.5μg/ml to 5μg/ml for the majority of Gram-negative organisms.4 The present investigation was undertaken to