FLUOROPHOTOMETRY IN CONTACT-LENS RESEARCH - THE NEXT STEP

Background, Fluorophotometry can be used to quantify changes in epithe lial permeability (P-dc), corneal pH, and tear exchange (T95; time to deplete 95% of a fluorescent dye from beneath a contact lens) associat ed with contact lens wear. Using fluorometric procedures, we present p reviously reported data in order to review the effects of contact lens wear on P-dc and pH, We also introduce a new method for measuring tea r exchange beneath a soft contact lens and present preliminary data, M ethods. P-dc was assessed on 32 subjects after 1 h of closed-eye soft contact lens wear. Stromal pH was assessed on 21 subjects wearing lens es with a range of different oxygen transmissibilities (Dk/L), T95 was assessed on 7 subjects who wore disposable lenses. P-dc estimates wer e derived by measuring the rate at which topically applied fluorescein crossed the epithelial barrier from the tears; corneal pH was quantif ied by alternately exciting a fluorescein-loaded cornea with two wavel engths of blue light and calculating the fluorescence intensity ratio (490/450 nm), which is pH-sensitive; and the T95 was estimated by appl ying 2 mu l of FITC-Dextran to the posterior surface of a soft contact lens and then monitoring the exponential decay of dye under the lens. Results, On average, 1 h of closed-eye contact lens wear caused a 41% increase in P-dc compared to the control eye. Corneal pH varied direc tly with a decrease in Dk/L, On average the T95 under contact lenses ( mean = 29 min) was slow compared to normal rates with no lens (approxi mately 5 min). Conclusions. Fluorophotometry can be used to quantify s ome interesting effects associated with contact lens wear, and the use of these techniques may provide new information about the impact of c ontact lens wear on corneal structure and function.