title: The association between pH level and corneal recovery from induced edema.
abstract: Corneal acidosis has been shown to reduce corneal hydration control (CHC) as measured by the rate, expressed as the percent recovery per hour (PRPH), at which the thickness of the cornea decreases exponentially after an increased hydration load. Since the effect of pH on corneal function is of scientific interest and may have clinical implications, we explored the relationship between pH and PRPH in greater detail by examining the effect of different stromal pH levels on corneal hydration control. Corneal edema was induced using a 90-min exposure to wearing a hypoxic contact lens (CL). Following removal of the CL, random assignment over four eye-test combinations of either 0, 3, 5, and 7% CO2 were made while pH and corneal thickness were monitored using slit lamp fluorophometry and optical pachometry to measure corneal pH and corneal thickness, respectively. From these measurements we determined the pH-dose/PRPH relationship. The average stromal pH +/- 1SD resulting from exposure to either the 0, 3, 5, and 7% CO2, was 7.65 +/- 0.11, 7.30 +/- 0.09, 7.15 +/- 0.08 and 7.04 +/- 0.07 (p < 0.001), respectively. Analysis based on a quadratic model of the dose-response relationship between PRPH and corneal pH indicates that PRPH is relatively unchanged for pH in the physiological range (pH = 7.40-7.65) and then decreases notably below the physiological range.
authors.affiliation: Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley 94720-2020, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Cohen
authors.forename: K A
authors.initials: KA
authors.lastname: Polse
authors.forename: R J
authors.initials: RJ
authors.lastname: Brand
authors.forename: J A
authors.initials: JA
authors.lastname: Bonanno
mesh_terms: D000138:Acidosis; D000293:Adolescent; D000328:Adult; D001834:Body Water; D002245:Carbon Dioxide; D015687:Cell Hypoxia; D003261:Contact Lenses / Q000009:adverse effects; D003315:Cornea / Q000502:physiology*; D015715:Corneal Edema / Q000209:etiology / Q000503:physiopathology*; D003319:Corneal Stroma / Q000503:physiopathology*; D005260:Female; D015590:Fluorophotometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D010101:Oxygen Consumption
chemical_list: D002245:Carbon Dioxide