DIFFUSION-COEFFICIENT THROUGH THE BLOOD-AQUEOUS BARRIER USING A STANDARD PROTOCOL

Aims/Background-Comparison of the diffusion coefficient through the bl ood-aqueous barrier of healthy volunteers measured in different cities with identical fluorophotometers using a standardised protocol. Metho ds-Healthy volunteers aged between 20 and 70 years were studied in sev en European cities. The fluorescein concentration in the anterior segm ent of each eye was measured with a commercial scanning fluorophotomet er 30 and 40 minutes after intravenous fluorescein. The decay of non-p rotein bound fluorescein concentration in blood plasma was determined with the use of three blood samples taken at 7, 15, and 55 minutes aft er injection. The diffusion coefficient through the blood-aqueous barr ier was calculated from the ratio between the fluorescein concentratio n in the anterior chamber and the time integral of nonprotein bound fl uorescein concentration in plasma using specially developed software. Results-The mean values of the diffusion coefficient (SD) (X 10(-4) mi n(-1)) were 4 . 76 (1 . 51) (n = 20, Brussels), 5 . 48 (2 . 33) (n = 1 7, Coimbra), 3 . 47 (2 . 09) (n = 12, Cologne), 6 . 09 (2 . 77) (n = 2 1, Frankfurt), 3 . 85 (1 . 59) (n = 11, Ghent), 4 . 99 (1 . 69) (n = 2 3, Leiden), and 4 . 87 (1 . 05) (n = 20, Madrid). The values between c entres were similar (Kruskal-Wallis test p > 0 . 05) except for Cologn e and Frankfurt (p = 0 . 013). No differences were found when repeatin g measurements (four centres, interval time 1-8 months, Wilcoxon paire d test p > 0 . 39). Conclusion-The diffusion coefficients had similar values and standard deviations. The concerted action demonstrated Germ any the usefulness of a standardised protocol.