Diabetic Retinopathy

The high blood sugar level in the blood vessels damages the cellular lining of the vessels resulting in a cascade of tissue damages and inflammatory responses. Unfortunately, the damages are not apparent (subclinical) in the early stage of the disease. Similarity can be drawn between damages in blood vessels caused by DM and disposing of corrosive agents (e.g. acid) down the ageing drains at home. It takes years before the pipes show any signs of crack or leaks just like diabetic retinopathy. At this point, the damages may not be irreversible or irreparable.

With uncontrolled DM, damages are done to large/medium sizes vessels (e.g. heart, aorta, and carotid vessels) and small vessels (e.g. eyes, kidneys, and brains), leading to ischaemic heart diseases (e.g. angina or heart attacks), aortic aneurysms, carotid lipid plaques, diabetic eye diseases, kidney failure, or strokes.

Diabetes affects the eyes in many different areas, from the front to the back of the eyes and even to the nerves behind the eyes. This results in increased incidences of corneal infection, cataract formation, vitreous haemorrhage,  swelling or bleeding in the retina (the light-sensitive part of the eye like the camera film or chip), or ischaemia of the optic nerve etc.

Diabetic retinopathy is the result of damage to the retina from prolonged elevated blood sugar in the small blood vessel behind the eye. Initially, patients will have no symptoms as the retinal function is compensated or the damages are affecting only the peripheral vision; this results in the retinopathy being left undiagnosed and the patients have a false sense of security. Eventually, the centre of the vision becomes involved and the vision is reduced with a drop in visual acuity. This could be caused by swelling in the centre of the retina (diabetic macular oedema), lack of blood to the retina (ischaemic retinopathy), abnormal growth of retinal vessels (proliferative diabetic retinopathy or new vessels formation), and bleeding into the gel in the middle of the eye (vitreous haemorrhages). All these result in visual loss or blindness and this could permanent if left untreated.

The Diabetic Retinopathy Study and the Early Treatment Diabetic Retinopathy Study in the 1970s and 1980s (international clinical trials) which in turn led to retinal laser photocoagulation being regarded as the standard treatment for the next 30 years. Laser treatment has potential side effects, and better treatment was eventually found. About ten years ago, effective treatment was discovered for treatment of the wet form of age-related macular degeneration (wAMD) in the form of eye injections (intravitreal injections) of a specially designed protein the halt the growth and leakage of abnormal blood vessels. These monthly injections (e.g. Avastin, Lucentis, and Eylea) have reduced the blindness caused by wAMD around the world. Extensive clinical trials have been conducted since

then and found that these drugs are also extremely effective in the treatment of diabetic retinopathy. Intravitreal injections are now the gold standard in the treatment of diabetic macular oedema and many cases of proliferative diabetic retinopathy. Patients will require monthly injections initially, once the diabetic eye disease is stabilised, injection frequency is reduced provided continuous clinical visit and monitoring is achieved. These injections have revolutionised the management of diabetic retinopathy and the trials have shown that the vision in these patients was preserved or improved.

At the Queensland Eye Institute, your retinal specialists will guide you on the most appropriate management of diabetic retinopathy. This depends on the severity of the diabetic eye diseases, which may merely be tightening up the diabetic (sugar level) control and monitoring of the retinopathy to regular intravitreal injections, and occasionally ocular surgery to removed blood inside the eyes (vitrectomy) in advanced stages of the diseases.