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Purpose: The cornea is frequently associated to hypoxia, whether during residence in the heights or more often when wearing contact lenses. To evaluate the corneal modifications induced by hypoxia at an infraclinical stage, we have used redox fluorometry that enables to study in vivo the metabolic response of the cells while measuring the fluorescence of the flavoproteins (FAD) of the corneal cells., Methods: The variations of the corneal fluorescence were studied in 12 healthy subjects, before and after a topically-induced 5-minute corneal hypoxia, submitting 2 eyes to a prehumidified flow of nitrogen 100%. The results were compared to those found in the same subjects after exposure under the same conditions to an ambiant air flow (N2 = 69%; O2 = 21%). The measurements of the corneal fluorescence were carried out with the fluorophotometre Flurotron Master FM2., Results: The authors did not find any statistically significant difference in the corneal fluorescence between the right and the left eyes of these 12 subjects, whether under normal conditions, under hypoxia, or under air flow (wilcoxon T-test, Friedman test)., Conclusion: As there are no significant results, these authors suggest that the chosen exposure time, although sufficient in vitro to induce a modification of the fluorecence of the cellular flavoproteins, may be too "short" in vivo. The use of complementary filters with the FM2 system would yield more information. The study of these results led the authors to broaden their search whether by looking for conditions for general hypoxia (hypobarric box) or by increasing local hypoxia (contact lenses).

Among various fluorophotometric methods performed on the anterior segment, topical administration of fluorescein was developed. This local administration allows to measure the aqueous humor flow and the permeability of the corneal endothelial. The examinations are performed on a computerized fluorophotometer: the Fluorotron Master. This fluorophotometer has been designed to accurately measure fluorescein's concentrations into the eye and especially in aqueous humor and cornea. Anterior chamber adapter magnifies the scan for detailed work in the anterior chamber and lens. The Fluorotron is supplied with a cuvette holder and a cuvette which is adapted to the optical head for measuring the concentration of fluorescein in blood plasma or in buffered aqueous samples. A good linearity was obtained between the meter readings and the concentrations of fluorescein in phosphate buffer with pH 7.4, within the range between 1 ng and 1000 ng. Based upon the mathematical analysis of Yablonski the method by fluorescein instillation is simple and safe and gives the loss coefficient, ko, of the dye from the anterior chamber, the aqueous humor flow, F, and the endothelial transfer coefficient kc.ca. Calculations were carried out on twenty one normal eyes yielding average values for F 2.97 +/- 0.93 microliter.min-1 (Mean +/- S.D.) and for kc.ca 4.02 +/- 0.40. 10(-1) min-1. These values are comparable to those of other authors.

The effects of various drugs on the human aqueous humor flow were studied by the fluorophotometric method of Yablonski (topical fluorescein instillation). The effect of the beta-adrenergic blocker (Timolol) on aqueous humor flow and on intra-ocular pressure has been studied in ten normal eyes on the Fluorotron Master. We found that the acute decrease in intra-ocular pressure was equal to 1.39 +/- 0.44 microliter.min-1 for the Timolol treated eyes, and equal to 2.79 +/- 0.57 microliter.min-1 for the untreated eyes (Placebo). The difference between Timolol and Placebo was statistically significant (Student t-tested, and Wilcoxon W-tested). The fluorophotometric method is superior to the tonographic method by giving a more favorable condition to study the facility of outflow in steady physiological state. Our results are in good agreement with other authors and show Timolol to have little or no effect on the facility of outflow.