Effects of intensified insulin treatment on retinal vessels in diabetic patients

Abstract

Forty-five diabetic patients were randomly assigned to treatment with continuous subcutaneous insulin infusion (CSII), multiple injections (MI), and conventional insulin treatment (CI). They were prospectively followed up for one year. A computerised scanning microdensitomter was applied on fundus photographs of retinal vessels, and we studied changes in calibres of the blood column (W0) and in width (Wr/W0) and intensity (Ir) of the central light reflex'. After six months of improved metabolic control the Ir was reduced in both MI and CSII cases compared with CIT cases (p<0·01), indicating haemorrheological changes in the retinas. Within these six months cotton-wool spots appeared in half the patients (n=15) on CSII and MI, but not in CIT patients. Subjects who developed cotton-wool spots, compared with those who did not, had greater intensities of reflection and larger calibres of vessels at the start of the study (p<0·01). On intensifying the treatment they were characterised by a larger fall in hemoglobin A1 (p<0·01) and by a larger decrease in Ir on arteries (p<0·05) and veins (p<0·01). The behaviour of the retinal circulation is different in patients developing transient ischaemic lesions on intensified insulin treatment from its behaviour in those who do not.