Diurnal variation of corneal autofluorescence in normal and diabetic eyes

Purpose To examine the diurnal variations in corneal autofluorescence in no rmal and diabetic patients. Methods We measured corneal autofluorescence using a fluorophotometer fitte d with an anterior segment adapter. Corneal autofluorescence was measured 1 0 times at 3 min intervals to evaluate the reproducibility of this instrume nt in 4 eyes of 4 normal subjects. The diurnal variation in corneal autoflu orescence was determined by measuring the fluctuations in 10 eyes in 10 nor mal subjects and one unoperated eye each of 10 patients with proliferative diabetic retinopathy (PDR). We performed five consecutive measurements at 1 000, 1130, 1400, 1630 and 1900 hours. The mean value of five measurements, the variation range and the coefficient of variation were analysed. Results The mean coefficient of variation in the measurement using this ins trument was 8.6 +/- 1.0%. In the patients with PDR, the mean corneal autofl uorescence value was significantly higher (p < 0.001), the variation range was significantly wider (p < 0.001) and the coefficient of variation was si gnificantly greater (p < 0.01) than in the normal subjects. Conclusions The results of this study suggest that corneal autofluorescence Changes over the course of a day in patients with diabetes. This may be ca used by the breakdown of the blood-aqueous barrier that we reported previou sly.