Diabetic retinopathy is a disorder of the back of the eye caused by diabetes mellitus, a condition associated with a high blood sugar level. Diabetes Mellitus can occur in early life and is then often referred to as Type 1 diabetes (this usually requires insulin treatment) or later in life, when it is often referred to as Type 2 diabetes (this usually requires treatment with diet adjustments and tablets).
How does diabetes affect the eye?
Diabetes damages the small blood vessels at the back of the eye. As a result of long-term high or unstable blood sugar levels, two changes occur in small blood vessels:
1. The very small blood vessels become narrowed which reduces the blood supply to the retina. The retina responds by producing molecules that stimulate the formation of new blood vessels (referred to as “neovascularization”). The “new” blood vessels are fragile and bleed easily resulting in a vitreous haemorrhage (a collection of blood within the jelly at the back of the eye, in front of the retina). After bleeding, the vessels contract and can pull on the retina resulting in a “tractional retinal detachment”. Both these conditions may result in visual loss.
2. The blood vessels of the retina become leaky causing fluid to accumulate in the central part of the retina (the macula, which is responsible for detailed vision and colour vision).
The most important factor in both preventing and controlling diabetic retinopathy is good long-term control of your blood sugar. The following are also important factors:
- blood pressure control
- blood cholesterol level control
- avoidance of smoking
The mainstay of treatment for sight-threatening diabetic retinopathy is retinal laser treatment. The laser treatment for diabetic retinopathy involves creating laser scars on the retina. This treatment is done as an out patient. For some patients, injections are given into the vitreous to reduce neovascularization. This treatment is also done as an out patient. Some patients with persistent leakage at the macula may benefit from intra-vitreal steroid injections, such as treatment with the Ozurdex® implant.
Surgery is used for advanced disease to manage persistent vitreous haemorrhage or retinal detachment.