Prolongation of the retinal mean circulation time in diabetes
N. P. Blair, G. T. Feke, J. Morales-Stoppello, C. E. Riva, D. G. Goger, G. Collas and J. W. McMeel
Retinal mean circulation time (MCT) and vascular sizes were measured in 21
normal individuals and 32 individuals with diabetes, and segmental blood
flow (SBF) was calculated. The MCT was similar in the normal individuals
(4.0 +/- 1.1 s) and the individuals with diabetes (4.2 +/- 1.9 s) when
seven individuals with diabetes with prolonged but not quantifiable MCT
were excluded. Including them by nonparametric statistics revealed that MCT
was significantly longer in individuals with diabetes with proliferative
retinopathy than in normal individuals or in individuals with diabetes with
nonproliferative retinopathy. The prolonged MCT correlated significantly
with advanced retinopathy as judged by leakage, neovascularization, and the
need for photocoagulation therapy. Reduced SBF may account for the
prolonged MCT, since the increase in vascular sizes observed failed to do
so. However, pathologic vascular changes may alter the relation between SBF
and MCT. Irrespective of implications about SBF, prolonged MCT, which
indicates marked circulatory disturbance, represents an important new
observation in diabetic retinopathy.
