Calcium dobesilate does not prevent diabetes patients with mild-to-moderate diabetic retinopathy from progressing to clinically significant macular oedema (CSME), which may lead to blindness. These findings, from the CALDIRET study, are reported in an Article published in this week's edition of The Lancet.
Diabetic retinopathy is damage to retina caused by the complications of diabetes, namely haemorrhaging of blood as new blood vessels form, which can eventually lead to blurred vision. CMSE occurs when diabetic retinopathy progresses, and occurs when fluid and protein deposits collect near or at the macula of the eye, a central area of the retina, causing it to thicken and swell. The swelling may affect a person's vision, as the macula represents the part of the retina at the back of the eyeball relevant for visual acuity and color vision.
Some 50% of patients with type 1 diabetes and 30% of those with type 2 diabetes develop sight-threatening retinopathy during their lifetime, despite the availability of several effective treatment options, such as laser therapy or eye surgery. In the CALDIRET study, Dr Christos Haritoglou, Ludwig-Maximilians-University, Munich, Germany, and colleagues assessed the effectiveness of calcium dobesiliate, which they proposed could stabilise the blood-retina barrier and therefore prevent leakage from blood vessels, provide an protective effect for blood vessels and positively influence growth factors, which play an important role in the development of CSME.
This randomised controlled trial, in 40 centres in 11 countries, enrolled 635 patients with type 2 diabetes and mild-to-moderate diabetic retinopathy. Of these, 324 received calcium dobesilate and 311 placebo. The researchers found more patients (86) developed CMSE in the calcium dobesilate group than in the placebo group (69), with analysis showing patients receiving the study drug were actually 32% more likely to develop CMSE than those given placebo. In post-hoc analysis (ie. Analysis of previously undefined sub-groups of patients after the trial), the authors saw a slight benefit in women with risk factors for vascular disease (HIGH BLOOD PRESSURE?), but say 'this interpretation remains speculative'.
The authors conclude: "Our findings showed that calcium dobesilate could neither prevent occurrence of CSME nor reduce probability of developing CSME during the 5-year follow-up period in patients with type 2 diabetes and mild-to-moderate non-proliferative diabetic retinopathy."
In an accompanying Comment, Dr Anna B Einarsdóttir, and Dr Einar Stefánsson, University of Iceland and Landspitali, National Hospital, Reykjavik, Iceland, say: "We should distinguish between the prevention of retinopathy and the prevention of diabetic blindness. Diabetic blindness can be reduced or prevented without reducing retinopathy. Systemic screening for diabetic retinopathy and preventive laser treatment for those who develop macular oedema or proliferative retinopathy reduces the rate of blindness to about 0.5% in the diabetic population, regardless of the prevalence of retinopathy."
Dr Christos Haritogolou, Ludwig-Maximilians-University, Munich, Germany T) +49 89 5160 3811 E) christos.haritoglou@med.uni-muenchen.de
Dr Einar Stefánsson, University of Iceland and Landspitali, National Hospital, Reykjavik, Iceland T) +354 824 5962 E) einarste@landspitali.is
For full Article and Comment see: http://press.thelancet.com/CALDIRET.pdf
Journal
The Lancet