Diabetes is one of the leading causes of blindness. Read on to know how the eye gets involved.

“Laughter is the best medicine, unless you're diabetic; then insulin comes pretty high on the list.” Jasper Carott

Diabetes mellitus is a growing problem in India. With an estimated 50.8 million people living with diabetes, India has the largest diabetic population. In a diabetic, the high glucose levels in the blood can cause harm to most organs like the heart, arteries and veins, the eyes, kidneys, brain and nerves.

Diabetes mellitus is one of the leading causes of blindness. Diabetic eye disease primarily encompasses diabetic retinopathy and cataract, which lead to either reversible or irreversible loss of vision.

The longer the duration of diabetes, the greater is the risk of developing diabetic eye disease.

Progression is rapid in patients with uncontrolled blood sugar. Similarly high blood pressure, increased blood lipid, renal disease, pregnancy, anaemia and smoking also have an adverse effect in the progression of diabetic retinopathy.

Diabetic retinopathy

The retina is the back portion of the eye. The retina along with optic nerve connects the eye to the brain. The high blood sugar damages the cells lining the walls of the arteries and the veins of the retina. These small blood vessels may balloon in some places to form micro-aneurysms that leak fluid, blood and fat into surrounding tissues. The fluid accumulation leads to thickening of retina. When it affects the central part of the retina known as the macula, there will be a drop in vision. The function of blood is to supply oxygen to the tissues. Since the blood vessels of the retina are damaged, the oxygen supply to the retina is deprived. New blood vessels start growing in an effort to supply nutrients and oxygen to the tissues. These new vessels grow on the surface of the retina and into the vitreous, a jelly-like fluid inside the eye. Unfortunately these new vessels are extremely fragile and leaky, leading to bleeding inside the eye or vitreous haemorrhage. Scar tissue also accompanies the growth of new vessels. In advanced stages this scar tissue can contract pulling the retina along, leading to detachment.

Cataract

The lens helps in focusing light rays to get clear vision. When this lens gets opacified, it results in a cataract. In addition diabetic patients develop earlier cataracts and may require surgery to replace it with a new intra ocular lens. Sometimes, in uncontrolled diabetes, high blood sugar causes swelling of the lens. This results in temporary blurring of vision. Once the blood sugar is brought under control and remains stable for one week, vision will improve.

Treatment options

Timely treatment helps prevent further vision loss. Laser remains the mainstay of treatment for diabetic retinopathy.

For fluid accumulation in macula, laser photocoagulation in focal or grid pattern can be applied. For new vessel formation (proliferative diabetic retinopathy), panretinal laser photocoagulation reduces the oxygen demand for retina.

Hence the impulse to form new vessels is knocked off. Laser treatment is often done to prevent complications related to diabetic retinopathy but not to improve vision.

Steroids and anti-vascular endothelial growth factor (anti-VEGF) drugs are being injected directly into the eye these days in patients with certain types of macular thickening. This blocks vascular endothelial growth factor, which plays a role in the growth of new vessels.

These injections help reduce blood vessel leakage and formation of abnormal new vessels. If needed these injections are repeated at intervals of 4-6 weeks.

For advanced diabetic eye disease, surgical intervention is considered. Sutureless vitrectomy is the latest procedure in which blood and scar tissue inside the eye is removed. Laser treatment is often combined with surgery in such patients. Cataract needs surgical removal.

Hence diabetic eye problems are treatable if diagnosed early. Diabetic patients should undergo yearly examinations even if they have good vision.

Last but not the least, lifestyle management helps reduce the risk of developing type II diabetes. It can also slow or halt progression of pre-diabetes to diabetes.

Symptoms

In early stages there will not be any blurring of vision.

If the patient develops fluid accumulation in the macula they will find a drop in vision.

Sudden deterioration in vision in advanced stage can occur due to bleeding inside the eye and retinal detachment.

Temporary change in refractive error sometimes occurs due to rapid shift in blood sugar.

Glare and blurring of vision could be noticed due to cataract.

When to consult an ophthalmologist?

Don't wait for symptoms. If you are diabetic, undergo a detailed eye examination during diagnosis itself. A yearly follow up is mandatory.

If you have diabetic retinopathy further follow up is as per ophthalmologist's advice.

Patients who undergo laser treatment should have follow up every three months.

Diabetic patients who become pregnant are also at risk of developing diabetic retinopathy. Seek an ophthalmologist's opinion in the first trimester.

Diabetic retinopathy patients with hypertension or renal disease should have regular ophthalmic check up every six months.

Preventive measures

Strict control of blood sugar is the mainstay. Your HbA1C levels should be around six per cent.

A healthy lifestyle including diet control and regular exercise helps avoid further complications.

Intensive control of blood pressure, renal function and serum lipid levels.

Blood haemoglobin should be within normal limits.

Avoid smoking.

E-mail: rajaneye@vsnl.com