Seventy-year-old Alan has had diabetes for many years.

He had suffered a heart attack and stroke previously, but his vision remained clear.

So he was understandably shocked when I broke the news that he had vision-threatening severe proliferative diabetic retinopathy. Unless he underwent immediate surgery, Alan would lose his sight within the next few weeks and eventually go blind.

Like him, many diabetics are unaware that the disease has wide-ranging effects on the body that can lead to chronic disabilities.

The longer a person lives with diabetes, the greater their risk of developing complications that affect the heart, blood vessels, eyes, kidneys, nerves and teeth.

Diabetic retinopathy is a disorder of the blood vessels in the retina, or the back of the eye.

In its early stages, there are no symptoms. Over the years, tiny blood spots or fatty deposits appear on the retina. They can turn into proliferative retinopathy, where new blood vessels grow on the surface of the retina and optic nerve.

These immature blood vessels tend to rupture and bleed into the eye cavity. Scar tissue then develops, contracts and pulls on the retina, causing retinal detachment and vision loss.

In some cases, new blood vessels grow on the iris, which contains muscles that allow the pupil of the eye to dilate or constrict to regulate the amount of light entering the eye. This causes a form of glaucoma, which can lead to blindness.

As diabetic retinopathy progresses, gradual blurring of vision develops, but this happens so slowly that many patients do not notice it.

This is a common complication of diabetes, with clear and established guidelines for treatment.

Diabetics in Singapore are going blind unnecessarily because they are unaware of the condition. About 180,000 of 600,000 diabetics aged 18 to 69 have diabetic retinopathy, but only 30,000 have been diagnosed. This is a worryingly large gap that can only be bridged with regular eye screening, which involves scanning the retina with a retinal camera. Those with diabetes should have their eyes screened at least once a year.

Early detection and prompt treatment offer them the best chance of preserving their vision.

PRESERVE VISION

Alan was referred to me by the Singapore Integrated Diabetic Retinopathy Programme, which screens diabetic patients for diabetic retinopathy at polyclinics islandwide.

After examining him, I told him there was only one way to preserve his vision - laser surgery.

Fear and denial prevent many people from realising that diabetic retinopathy is irreversible if treated late. It was difficult for Alan to say yes to surgery at first, as he could not sense anything wrong with his vision. He eventually took a leap of faith and underwent a procedure called scatter laser treatment, where up to 2,000 laser burns are placed on the retina to seal or remove abnormal leaking blood vessels. The procedure was done in several 30-minute sessions over two months, due to the high number of laser burns required.

Not only did Alan undergo surgery, but he also sought to change his lifestyle. At 70, it was no mean feat changing his diet and exercising more, but he persevered. Five years on, at 75, he has kept his vision, and goes for yearly checks. He is frail but generally in good health.

Research has shown that those with diabetes who keep their blood sugar levels as close to normal as possible will keep diabetic retinopathy at bay longer, and have fewer kidney and nerve problems.

I often tell my diabetic patients that they are like a ship with a leak. If the hole is not plugged, the ship will sink.

If they do not eat healthily, exercise regularly, undergo regular eye screening and take their medication, they will have trouble averting complications such as diabetic retinopathy. Alan was lucky that the hole in his ship was repaired in the nick of time.

•Associate Professor Ian Yeo is the deputy medical director (education) and head and senior consultant at the medical retina department, Singapore National Eye Centre.