Measurement of aqueous humor flow following scleral injection of sulfacetamide as marker: effect of methazolamide, timolol, and pilocarpine.
A simple technique for rapid determination of the flow of aqueous humor (AH) in rabbits is described. Data from control eyes and eyes treated with known inhibitors of aqueous humor production are presented as evidence of the suitability of the technique for comparing the influence of other drugs on aqueous flow. The flow measurement depends on marker dilution by fluid turnover during the first 30 min after 5 microliters marker solution is delivered to the anterior chamber. This is done by passing a needle through the sclera and behind the iris. The advantage of this route is that it permits withdrawal of the needle after delivery without leakage of marker or aqueous humor. Sulfacetamide (SAC), a sulfonamide with low lipid solubility and pKa 5.4, is the marker of flow used here. Control flow data from SAC, fluorescein (FL), reactive blue-2, and 14C-inulin as markers were compared. The control flow measured with SAC in two independent groups is 3.91 and 3.40 microliters/min or 3.69 +/- 0.37 S.E. overall. The data show that inhibition of carbonic anhydrase (CA) in ciliary processes by systemic methazolamide reduces flow 38%. Topical timolol reduces flow 35%. Pilocarpine, which is known to decrease IOP largely by increasing outflow facility, did not significantly reduce flow. This system for measuring AH flow allows rapid accumulation of data for topical, intracameral or systemic treatments.
Vogh
B P
BP
University of Florida College of Medicine, Department of Pharmacology and Therapeutics, Gainesville.
Godman
D R
DR
Maren
T H
TH
D000818:Animals; D001082:Aqueous Humor / Q000502:physiology*; D015415:Biomarkers; D008297:Male; D008704:Methazolamide / Q000494:pharmacology; D010862:Pilocarpine / Q000494:pharmacology; D011817:Rabbits; D015203:Reproducibility of Results; D012590:Sclera; D013409:Sulfacetamide / Q000008:administration & dosage; D013997:Time Factors; D013999:Timolol / Q000494:pharmacology
D015415:Biomarkers; D010862:Pilocarpine; D013409:Sulfacetamide; D013999:Timolol; D008704:Methazolamide