Strict control ofglycaemia: effects on bloodflow inthelarge retinal vessels andinthemacular microcirculation

Aims-Thepurposeofthisstudywasto investigate theeffect ofinstituting strict diabetic glycaemic control ontheretinal macular microcirculation andtocompare thiseffect withthatobserved inthemain retinal veins. Methods-In28insulin dependent diabetic patients withpoorglycaemic control aregimenofstrict diabetic control, consisting offourdaily insulin injections was instituted andmaintained for6months. Retinalhaemodynamics were investigatedinthemacularmicrocirculation by thebluefield simulation technique andin themajorretinal veinsbyacombination ofbidirectional laserDoppler velocimetryandmonochromatic fundus photography.Progression ofdiabetic retinopathy was assessed fromfundusphotographs takenatbaseline andattheendofthe study. Results-Institution of strictdiabetic control resulted inasignificant increase inleucocyte velocity inthemacularcirculation (p=0.013). Nosignificant difference in thisincrease was observed betweeneyesthatshowedprogression (n=8)and no progression (n=20)of retinopathy during thestudy. Significant correlations werefoundbetweenrelative changesover time of bloodflow measuredinthemainretinal veinsand relative changesofleucocyte velocity determined inthemacularmicrocirculationat2months(p=0.008) and6months (p=0.001) butnotat5days(p=0.49). In theeight eyesthatshowedprogression of retinopathy, theproductofleucocyte velocity and density at baseline was significantly higher than normal (p<005). Duringthelength ofthisstudy, thisproduct wasalsosignificantly higher intheeight eyesthatshowedretinopathy progression thaninthe20eyesthatdid notshowprogression (p=0.005). Conclusion-Our resultssuggestthat increased flowinthemacularmicrocirculation maybeassociated withprogression of retinopathy, thus supporting the hypothesis thatincreased bloodflowmay playaroleinthedevelopment ofdiabetic microangiopathy. Althoughthereare correlations betweenthechanges detected inthemacularmicrocirculation andthose measuredinthemainretinal vessels, therearealsodifferences whichneedtobe further investigated inordertobetter understand pathogenetic mechanisms. (BrJOphthalmol 1995; 79:735-741)