Letter to the EditorFactors affecting outflow facility calculations
Section snippets
Living monkey eyes
Data used in this section were selected from previous experiments in living cynomolgus monkeys, where F was measured by 2-level constant pressure (∼15/25 mmHg) perfusion of the AC (Bárány, 1964, Bárány, 1965). All the previous investigations were in accordance with University of Wisconsin and NIH guidelines for animal use, and with the ARVO Statement on the Use of Animals in Ophthalmic and Vision Research. Anesthesia for AC perfusion in the investigations was conducted as described previously (
Viscoelastic response
Schlegel et al. (1972) found that the unpressurized enucleated intact human eye consistently showed a large viscoelastic response (stress relaxation) during perfusion, which increased the volume of the eye. A volume increase in the AC will allow some additional fluid to flow from the external reservoir into the eye during perfusion. This fluid flow will be included in the measured F if pressure increases during outflow measurement, but it will not leave the chamber. Therefore, it may be called
Summary
Outflow facility (C) values determined by different perfusion techniques and methods of calculation were compared in order to clarify factors accounting for differences between the C values. Outflow data obtained by 2-level constant pressure perfusion in living monkeys or cultured monkey anterior segments were recalculated with formulas utilized in 2-level constant pressure perfusion and 1-level constant pressure or constant rate perfusion studies. Results for both the living monkey eye and the
Acknowledgements
This study was supported by grants from the NIH National Eye Institute (EY02698), Bethesda, MD; Glaucoma Research Foundation, San Francisco, CA; Research to Prevent Blindness, New York, NY; Ocular Physiology Research & Education Foundation, Madison, WI, and Allergan, Inc., Irvine, CA. Authors thank Dr. Ross Ethier for his thoughtful comments.
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