title: Effect of rigid contact lens oxygen transmissibility on stromal pH in the living human eye.
abstract: Corneal stromal pH was measured fluorometrically in nine human subjects after 1.5 hours of eye closure while wearing hard gas permeable contact lenses. Six lens types providing a wide range in oxygen transmissibilities (Dk/L)O2 from 0.15 to 55.0 X 10(-9) (cm ml O2/seconds of ml mmHg) were used. Stromal pH upon opening the eyes was directly related to (Dk/L)O2 and ranged from 7.01 to 7.26. These pH values were all significantly lower than the control (no lens), which had a pH of 7.38 (P less than 0.005). After eye opening (lens still on) stromal pH increased and reached a new steady-state (range, 7.11-7.45) in approximately 30 minutes; however, these pH levels were still below the control (no lens) (pH 7.54; P less than 0.005). The rate of pH change after eye opening also increased directly with (Dk/L)O2. The authors conclude that the lenses presently available provide insufficient gas exchange to prevent alteration of corneal pH and suggest that the measurement of stromal pH may provide a sensitive index for evaluating the metabolic effects of contract lens wear.
mesh_terms: D000136:Acid-Base Equilibrium; D000328:Adult; D001767:Blinking; D002245:Carbon Dioxide / Q000378:metabolism; D003261:Contact Lenses; D003315:Cornea / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D010101:Oxygen Consumption
chemical_list: D002245:Carbon Dioxide