The lower basal cell density found in patients with diabetes may result from a combination of different mechanisms including decreased innervation at the subbasal nerve plexus, basement membrane alterations, and higher turnover rate in basal epithelial cells. The lower cell density in the midstroma of diabetic patients and healthy controls may be attributed in part to differences in oxygen concentration in the stromal layers (depths). Changes in cellular density did not seem to be responsible for the increased autofluorescence in diabetes.

Aimns-The purpose of this study was to assess whether the preservative benzalkonium chloride (BAC 0.01%) present in timolol induced a decrease in basal tear turnover and a deterioration ofprecorneal tear film in patients with glaucoma and ocular hypertension using topical timolol. Methods In a previous study7 we demonstrated a 36% lower mean basal tear turnover in patients with glaucoma using timolol+BAC in comparison with that of healthy controls. The preservative BAC is suggested as a possible cause for this decrease in tear turnover. The present follow up study was initiated to verify this assumption.In this study the tear turnover and break up time (BUT) of the precorneal tear film of patients with open angle glaucoma and ocular hypertension were evaluated when using timolol+BAC and subsequently when using timolol-BAC. In this way we expected to find out if BAC could be held responsible for a decrease in tear production and for a deterioration of tear film stability in patients with glaucoma who use timolol+ BAC. The study was set up in such a way that the same patient was measured when using timolol+BAC as well as when using timolol-BAC in order to avoid the effect of interindividual spread in tear turnover values. Note that the fluorophotometric measurement of tear turnover with a computer fluorophotometer is a quantitative method for the determination of tear production7 and is, because of its objectivity and reproducibility, suitable for unbiased outcomes of the measurements. The precorneal tear film integrity determined by the tear film BUT and the subjective acceptability of timolol+BAC and timolol-BAC were also assessed. Material and methods PATIENTS

No abstract

The tear turnover in the different cities was similar. The methods used were simple and the software easy to use.

A simple quantitative and reproducible method for evaluating lens transmission (λ = 490 and 530 nm) is described. It is based on the measurement of autofluorescence in the anterior and the posterior part of the lens by means of a fluorophotometer, assuming an about equal fluorescence quantum efficiency in both parts. Consequently any difference in fluorescence between both parts can be attributed to a loss of exciting and fluorescent light in the lens. For both wavelengths, the average lens transmission is determined by this method in a normal population as a function of age.