Increased aqueous flare as a result of a therapeutic dose of mannitol in humans.

To evaluate the effects of mannitol on aqueous flare (aqueous protein concentration), we administered an intravenous clinical therapeutic dose to normal young adults (average age 20.1 years), to normal older adults (average age 61.5 years), and also to patients with diabetes mellitus, systemic hypertension, or pseudoexfoliation syndrome who were about to undergo intraocular surgery (average age 66.4 years). Protein and cell levels in the aqueous were determined with a device that measures laser light scatter in the aqueous. Mannitol increased the intensity of aqueous flare. In all subjects, the intensity of aqueous flare was greatest around 1 h following drug administration; the magnitude and duration of the aqueous flare increase were significantly greater in normal older adults than in normal young adults; the magnitude was essentially the same in older adults with and without disease. The effect reversed within 6 h of drug administration in normal subjects. We consider the findings to represent changes in actual aqueous protein concentration and discuss the possible causes of this phenomenon.