Intraocular pressure and aqueous humor formation rate have been determined from the first trimester of pregnancy through term, with further determinations 3 months postpartum, in 7 patients. The intraocular pressure showed a consistent, statistically significant fall during pregnancy, returning to values seen in early pregnancy after delivery. Aqueous humor formation rate showed no change during pregnancy. The data indicate that the sustained elevated hormonal levels during pregnancy, either directly or indirectly, cause an increase in fluid outflow conductance from the eye without altering the rate of fluid entry.

We determined the effects of either topical or systemic calcium channel antagonists on rabbit intraocular pressure (IOP). Topical nifedipine, verapamil or diltiazem had no significant effect on IOP. Intravenous verapamil and nifedipine caused statistically significant reductions in IOP between 2 and 6 h after administration; the nifedipine response followed an increase in IOP at 30 min. Diltiazem, given 3 times daily for 3 days, caused no pressure change. In the rabbit, therefore, calcium channel antagonists have no effect when given topically, but do reduce IOP when given systemically.

The uptake and washout kinetics of four drugs representing different classes of ophthalmic medications were measured in intraocular lenses of different materials. The materials ranged from hydrogel lenses to poly(methyl methacrylate) (PMMA), Acrysof (acrylic/methacrylic), and two types of silicone lenses (Chiroflex and AMO SI-18NB). Uptake was determined after seven days of immersion in a large volume of Ringer's solution containing drug concentrations that equaled those found in aqueous humor 30 minutes to one hour after topical administration. Washout was determined after placing lenses in 1 ml of 0.9% saline for 24 hours. Only hydrogel lenses could be digested in acid to measure lens uptake directly. The PMMA, Acrysof, and silicone lenses behaved similarly toward gentamicin and dexamethasone--low uptake (less than 3.5 ng/mg lens) and low washout (less than 4.0%). Their uptake of norepinephrine was lower (less than 0.7 ng/mg lens) but the washout varied from 29% (AMO silicone) to 100% (PMMA and Acrysof). The pilocarpine uptake was the lowest of drugs tested (less than 0.03 ng/mg lens) and the washout varied from 1.5% (acrylic) to 100% (PMMA and Chiroflex silicone). Hydrogel lenses took up the most drug in the following order: dexamethasone greater than pilocarpine greater than gentamicin greater than norepinephrine. Washout was high, ranging from 83% to 98%. Despite the greater uptake and washout, the maximum drug uptake would only provide one-tenth of the greatest aqueous humor concentration that occurs after topical drug administration. Intraocular lenses of the materials tested did not interfere with the intraocular drug pharmacokinetics, nor did the data indicate that presoaking intraocular lenses of these materials in drugs would enhance post-surgical intraocular drug concentrations.

No abstract