Q&A
What is diabetic retinopathy?
Why was the DIRECT Programme needed?
What was the main question the DIRECT Programme was designed to answer?
What were the different studies in the DIRECT Programme?
How were the studies in the Programme carried out?
How was diabetic retinopathy assessed?
What is diabetic retinopathy?
Diabetic retinopathy is the term for the changes that occur in the back of the eye (the retina) in diabetic eye disease. These changes are progressive and can lead to blindness.
Why was the DIRECT Programme needed?
Diabetic eye disease is the most feared complication of diabetes. There is no treatment specifically for diabetic retinopathy. Laser treatment can be used to manage severe retinopathy, but it is a destructive treatment that can itself cause visual loss.
Previous studies have shown that controlling blood pressure and blood glucose can help prevent the onset and reduce the progression of diabetic retinopathy. One study (the EUCLID study) found that a type of blood pressure lowering treatment that acts on the renin-angiotensin system (RAS) had a potentially beneficial effect on diabetic retinopathy independent of its blood pressure lowering effect. The DIRECT Programme was needed because no previous study had looked at the effects of RAS-blocking treatment on diabetic retinopathy as the primary focus.
DIRECT is the first large-scale programme of clinical trials to investigate the benefit of RAS-blockade with the aim of bringing hope to the large and increasing number of patients with diabetes, the majority of whom will be affected eventually by diabetic eye disease.
What was the main question the DIRECT Programme was designed to answer?
In relatively healthy patients with Type 1 and Type 2 diabetes, does medical treatment with candesartan cilexetil (a RAS-blocking treatment called an angiotensin receptor blocker) prevent, halt the progression of, or even improve diabetic retinopathy.
What were the different studies in the DIRECT Programme?
DIRECT-Prevent 1 was in Type 1 diabetes patients with no retinopathy at the outset, no kidney disease and normal blood pressure.
DIRECT-Protect 1 was in Type 1 diabetes patients with mild to moderate retinopathy at the outset, no kidney disease and normal blood pressure.
DIRECT-Protect 2 was in Type 2 diabetes patients with mild to moderate retinopathy at the outset, no kidney disease and either normal blood pressure or treated high blood pressure that was well controlled.
How were the studies in the Programme carried out?
Half of the participants were given one daily tablet of the active treatment, candesartan, and the other half were given an identical looking inactive tablet (placebo) for the duration of the Programme. This was allocated at random. The health of the participants, in particular the health of their eyes, was assessed at regular intervals over four years.
How was diabetic retinopathy assessed?
Photographs were taken of the retinas of participants at the beginning of the Programme and then annually for four years. Fourteen photographs were taken of each eye so that a large area of the retina was covered in simulated 3D (stereoscopic images). These photographs were inspected thoroughly for signs of diabetic retinopathy and graded according to an established scale of retinopathy severity.
For more information, see the video clip on the assessment of diabetic retinopathy in the DIRECT Programme.