Diabetic retinopathy is a condition caused by diabetes mellitus where blood vessels of the retina are damaged due to the high blood glucose level. Such damage to the blood vessels of the retina can result in abnormal bleeding (retinal haemorrhages), swelling of the retina (macular oedema), poor blood flow to the retina (ischaemia), and/or scarring of the retina. It can occur for both Type I and Type II diabetes. The longer you have had diabetes, the more likely you are to develop diabetic retinopathy. The less well-controlled the diabetes, the more likely it is also to develop diabetic retinopathy.
There are two types of diabetic retinopathy: non-proliferative diabetic retinopathy (NPDR) and a more severe form, proliferative diabetic retinopathy (PDR). In NPDR the damaged retinal blood vessels develop tiny weak areas called microaneurysms. Over time, these microaneurysms can rupture and leak, resulting in retinal haemorrhages (bleeding). Fluid, fats and protein from the blood stream can also leak into the retina and cause swelling (oedema) and hard exduates. Over time, poor blood circulation of the retina can also result in death of nerve cells (ischaemia). The combination of these processes can lead to permanent visual loss.
In proliferative diabetic retinopathy (PDR), the retina can produce substances that promote the growth of new, abnormal blood vessels (neovascularization) in response to the ischaemia. These new blood vessels are however fragile and tend to bleed into the vitreous or result in scar tissues that pull on the retina, potentially causing a very serious condition called tractional retinal detachment.
When diabetic retinopathy is diagnosed, you may need to undergo further investigations such as fluorescein angiography, OCT scan or OCT angiography to evaluate the severity of the condition. The purpose of these further investigations is to identify areas of macular oedema, ischaemia and neovascularisation so appropriate treatments can be applied. A B-scan ultrasound may need to be performed when the vitreous haemorrhage is very dense and the retina can not be examined properly.
The most important aspect in the treatment of diabetic retinopathy is adequate long-term control of blood glucose level. Patients should monitor their glucose daily and have their haemoglobin A1c level checked with a GP. Regular eye examinations are important as symptoms of blurred vision or floaters only appear long after diabetic retinopathy has developed. Therefore, early detection and treatment before the retina is severely damaged is the most successful in minimizing visual loss from diabetic retinopathy. It is also a good idea to keep blood pressure and cholesterol levels in check.
Intravitreal therapy such as Eylea, Lucentis, Avastin, and Triamcinolone may be necessary to treat macular oedema as well as new vessels in diabetic retinopathy. These drugs are highly effective, though regular review and treatment are required. Treatment may need to be repeated at regular intervals to continue long-term benefits. In some cases, these drugs may be combined with vitrectomy surgery.
PANRETINAL PHOTOCOAGULATION (PRP)
Panretinal photocoagulation laser surgery is performed in proliferative diabetic retinopathy patients to prevent severe vitreous haemorrhages and blindness. The laser causes regression of abnormal blood vessels which grow at the back of the eye on the retina in diabetic patients. Each laser session takes approximately fifteen to twenty minutes and multiple sessions are required. Usually three to four sessions per eye are required to treat the proliferative diabetic retinopathy. There is some discomfort during the laser, and analgesics such as Panadol or Panadeine may be taken before the laser session. With time, one may notice some decrease in night vision and peripheral vision which occurs due to the laser treatment. This is however necessary in order to control the proliferative diabetic retinopathy.
In some cases of severe diabetic retinopathy where laser surgery is unsuccessful, vitreoretinal microsurgery might be indicated. Vitreoretinal microsurgery in severe proliferative diabetic retinopathy involves the use of microsurgical instruments inside the eye to remove severe scar tissue and haemorrhage in the vitreous jelly. Laser treatment is also able to be performed during surgery and a special gas bubble is placed inside the eye which absorbs naturally over a few weeks. Vision may improve following surgery over several months, depending upon the state of the eye prior to the surgery. Risks with diabetic vitrectomy include further haemorrhages into the eye, retinal detachment and cataract formation which may occur after surgery. Any of these complications may necessitate further surgery.