Surface Tension of Aqueous Humor

Objective: To measure and compare the surface tension of aqueous humor in patients with and without glaucoma. Methods: The surface tension of aqueous humor was measured using a commercially available instrument and software that were validated by using a known fluid (deionized water and methanol). Analysis of aqueous and vitreous samples obtained from 20 rabbit eyes showed that the system could be used successfully for small amounts of ocular fluid. The effect of glaucoma drugs on the surface tension of aqueous humor was then studied in a rabbit model. Comparison of aqueous humor from 66 patients with glaucoma and 53 patients with cataracts but no glaucoma was carried out. Results: The surface tension of rabbit aqueous humor was 65.9 +/- 1.2; vitreous, 60.6 +/- 2.6; and balanced salt solution, 70.7 +/- 0.9. Timolol and latanoprost did not alter the surface tension of the aqueous humor in the rabbit model. The average surface tension of human aqueous humor was 63.33 +/- 4.0 (glaucomatous eyes) and 66.19 +/- 2.64 (nonglaucomatous eyes with cataracts) (P = 0.0001). Conclusions: A technique of measuring the surface tension from small quantities of aqueous humor is validated. Surface tension of the aqueous humor in glaucoma patients was less than that of cataract patients.