Diabetes affects many systems through its propensity to cause closure of minute blood vessels called microangiopathy. When this happens in the retina, the important light sensitive layer at the back of the eye, it is called diabetic retinopathy. Incidentally this is the most common cause of irreversible adult blindness in the industrialised world. The disease usually develops gradually and insidiously over years, with no effect on vision at the early stage. The duration of the disease and the control of blood sugar levels have an important bearing on the development and progress of this disease. The most dangerous period are those years when the patient has completely deranged blood sugars and has still not been diagnosed. There are patients who may be in this state for five to seven years presenting directly with diabetes related complications.
The practice of periodic preventive health checks, which have caught on over the years, have played an important role in early detection of diabetes. The credit of introducing this concept of health checks goes to the Apollo group, and more specifically to Dr. Prathap Reddy himself who introduced this at the Chennai Apollo a few decades ago.
Diabetic retinopathy can be broadly divided into two stages: non-proliferative & the more advanced proliferative. The basic problem is decreased blood supply to the retina. In the non-proliferative stage, leakage from ischemic capillaries is the hallmark, resulting in swelling of the retina (macular oedema), which can cause significant drop in vision. In the more advanced proliferative stage, the retina responds by development of new blood vessels. This can lead to bleeding into the jelly of the eye (vitreous haemorrhage) or development of elastic bands on the retina (traction retinal detachment). The natural course of all these developments is complete blindness.
Testing and Diagnosis
Fortunately, today medical science is equipped to handle these pathologies and restore sight completely. It is strongly recommended that all diabetic patients must have their retina checked once a year by a qualified eye surgeon, which would include a thorough retinal examination after dilation. Good control of sugars is the cornerstone of preventing onset of diabetic retinopathy, a fact doubly important for young diabetics. Your diabetologist will check you for other factors like anaemia, bad lipid profile, micro albuminuria, increased blood pressure and advise you against smoking. All these are often referred to as the bad cousins of diabetes. Beware of opting for cure by alternative medicine options, widely publicised by the lay press to a gullible public. In case your ophthalmologist feels you have diabetic retinopathy, he is likely to conduct some tests, notably FFA and OCT. Fundus Fluorescein Angiography (FFA) involves intravenous injection followed by pictures of the retina taken with a special retinal camera. Optical Coherence Tomography (OCT) is like a CT scan of the retina which detects presence of swelling in the macular area. These tests help your doctor to take a decision about your further treatment.
Patients with significant retinal ischemia are likely to be advised retinal laser treatment. This is non-invasive and may be directed to the retina through a slit lamp or an indirect ophthalmoscope. The treatment is backed by many years of experience and research studies, and is conclusively known to reduce the chances of progression to the next stage of vitreous haemorrhage and traction retinal detachment. Eyes with swelling in the macular area have a new hope in injection of anti VEGF drugs, which can reduce the leakage and chances of bleeding. Drugs such as macugen, lucentis or avastin have shown good efficacy in treatment of macular oedema. Eyes undergoing these treatments need to be followed up carefully on a long term basis. Further intervention may be warranted at a later stage in some patients, as the diabetes itself is not curable.
In situations where the disease has advanced to vitreous haemorrhage or traction retinal detachment, vitreous microsurgery forms the mainstay of treatment. The surgery is performed under an operating microscope. Micro instruments are used to remove the blood or fibrous tissue causing traction on the retina. Endolaser is used to treat areas of ischemic retina. The vitreous gel may be replaced by gas or silicone oil. Results of these surgeries are good & visual restoration depends on the extent of pathology being treated. Your retinal surgeon can give you a fair idea of the progress expected in your case during the pre-surgery counselling. Diabetes can predispose the eye to a plethora of ocular pathologies, such as early cataract, open angle glaucoma, acute ischemic optic neuropathy, ocular nerve palsies and orbital mucormycosis. To conclude, timely detection of diabetes followed by good control and periodic dilated retinal examination, hold the key to preventing severe visual loss due to diabetic retinopathy.