The instillation of 0.2% 9α-fluoro-16α-methylprednisolone (I) [50-02-2] twice daily in the left eye of rabbits for 30 days caused marked acidification accompanied by a decrease in the buffer base, a notable increase in osmotic pressure, and a decrease in the ascorbic acid content in the vitreous body. I also increased intraocular pressure, produced slight alkalosis of blood and significant alkalosis of the aqueous humor, and decreased the ascorbic acid content of the aqueous humor and lens.