Search

The permeability of the blood retinal barrier (PBRB) and the diffusion coefficient into the anterior chamber (kd) in 20 insulin dependent (ID) and in 11 non-insulin dependent (NID) diabetics with various degrees of retinopathy were determined by fluorophotometry with a 25% accuracy. The difference of PBRB and the kd values between the NID and the ID patients was not significant (p greater than 0.05 and p greater than 0.22). The mean PBRB and the mean kd values differed significantly from those of a healthy population (p less than 0.0013 and p = 0.025). A significant correlation was established between PBRB and diabetes duration (r = 0.55; p less than 0.01) but not between PBRB or kd values and metabolic control (HbAl) (p greater than 0.5) or creatinine clearance (p greater than 0.5). The time integrals of unbound plasma fluorescein in the diabetics between the time of injection and 1 hour later were comparable with those of healthy controls. The difference between the mean PBRB value of diabetics with advanced retinopathy and that of a healthy population was significant (p less than 0.003) but the difference for the mean values of diabetics with no or minimal background retinopathy was not (p greater than 0.2), indicating that PBRB values do not increase to an abnormal level while signs of diabetic retinopathy are absent on fluorescein angiography.

Two useful methods for determination of the decay curve of non-protein bound fluorescein (NPBF) in plasma up to 1 hour after intravenous fluorescein injection are described and evaluated. The course of NPBF is approximated in method 1 by a sum of two exponential decay functions and in method 2 by a power of time function. The parameters in these functions are calculated with the use of concentration values measured in two blood samples taken at about 5 min. and 60 min. after injection. Calculations in method 1 include the amount of fluorescein injected. The accuracy of each method was evaluated in 7 volunteers by measuring NPBF concentration in 15-28 blood samples taken after fluorescein injection at intervals of 5 min. or less. The mean relative deviation between calculated and measured concentration values amounted to 9.2% +/- 4.3 SD and 12.7% +/- 4.5 SD for method 1 and 2, respectively. The time integral of NPBF concentration in plasma up to one hour after injection was calculated according to the results of both methods and compared with integral values obtained by linear interpolation between concentration values measured in the 15-28 plasma samples. The mean relative deviation for the 7 volunteers amounted at 15 min. to 2.8% and 17% and at 60 min. to 11% and 18% for method 1 and 2, respectively. The maximal difference between the blood-retinal barrier permeability value for NPBF calculated with and without taking glucuronation into account was estimated to be 20% for an average glucuronation percentage of 70% or less.