A truck driver's blind spot

PUBLISHED : Tuesday, 11 September, 2012, 12:00am
UPDATED : Tuesday, 11 September, 2012, 9:31am

A cross-border truck driver's life is tough and often unhealthy. Most will grab the tastiest fast food they can and then sit for 12 hours straight, only taking short breaks to stretch or visit the toilet.

Although at risk of developing a range of health problems, few long-haul truck drivers have the time, money or inclination to have regular check-ups.

That was 44-year-old Benson Kong's lifestyle, until an accident last year landed him in the emergency room, where doctors discovered that he had diabetes.

Kong (whose name has been changed for patient confidentiality reasons) saw this as a wake-up call and resolved to treat his body better. He changed his diet and dutifully took his medication to manage his blood sugar. But given his job's demands, regular exercise was still a challenge.

Because Kong had never had a thorough health check, no one knew how long his blood glucose level had been out of control.

Unfortunately, it did not occur to his family doctor, who helped monitor and manage his condition, that the disease might have started damaging his organs.

It was not long before Kong noticed problems with his vision, especially in his right eye. He started having trouble reading newspapers and watching television. He visited an optician to have new glasses made, but he continued to feel like he was looking at the world through a thick pane of unpolished glass.

When he could not see road signs clearly, putting his livelihood at risk, he knew he needed help. Kong went to see Dr David Liu Ta-li, associate professor of the Chinese University's ophthalmology department.

By that time, the vision in Kong's right eye had become severely distorted. Not only did the world appear blurry, but straight lines also appeared curved and a persistent shadow clouded the centre of his vision. He had to take extended leave from work.

When Liu examined Kong's eye, it was apparent that his macula was badly swollen. The macula is the centre of the retina where a high concentration of photoreceptors, or sensory cells that respond to light, provide 95 per cent of high-resolution central vision.

The macula also acts as the eye's natural sunblock.

The excess glucose in Kong's bloodstream was modifying proteins and lipids into substances that damage blood vessels, including those at the back of the eye, setting off a damaging chain of events in the macula.

Fluids within the compromised blood vessels start to leak into the macula, making it swell. Proteins and serum also flood into the macula, causing inflammation which further aggravates the swelling. This condition is called diabetic macular edema (DME).

Swollen and inflamed, the macula in Kong's right eye could no longer properly interpret light into the signals that enable our brains to see, resulting in visual distortions.

Diabetic macular edema is the most common cause of vision loss in diabetic patients. According to the US-based International Diabetes Federation, some 14 per cent of diabetic patients have DME, which does not present any symptoms in the early stages.

Without treatment, some 25 per cent of those patients will have severe deterioration in their vision within three years.

Using a retinal scan called optical coherence tomography, Liu found that Kong's macula had ballooned to double its normal size.

Kong had lost 90 per cent of normal vision in his right eye, and 10 per cent in his left. If his condition was left untreated, DME would eventually cause Kong to go blind.

The ophthalmologist presented two treatment options for Kong: the conventional laser treatment or an intra-ocular injection.

The first option, laser, in theory stimulates the retinal cells in the macula to reabsorb excess fluid and pump it away. But it carries a risk: the laser treatment can also damage normal tissue and lead to some vision loss.

It was, however, affordable at about HK$50 per session at a public hospital. People with clinically significant DME may require three to four different laser sessions at two- to four-month intervals to stop the macular swelling.

Meanwhile, an intra-ocular drug called anti-vascular endothelial growth factor (anti-VEGF) presented a more effective and low-risk option.

VEGF is a molecule that mediates leakage in blood vessels and is naturally present in the body to help restore oxygen supply to tissues when circulation is poor. When the molecules become too excessive under DME, anti-VEGF can wipe out the surplus protein.

However, the treatment is vastly more expensive. It costs HK$9,000 per injection, with a recommended course of four to six monthly injections for successful results.

Kong could not afford the anti-VEGF treatment, which is not subsidised by the government even at a public hospital. He opted for the laser treatment - but even after weeks of treatment, Kong still could not see well.

Frustrated, he turned his efforts towards securing funds for the anti-VEGF treatment. It took him a few months before he could finally pay for the injections.

Under this method, anaesthetic eye drops are first used to numb the eye before a fine needle delivers the drug. Kong responded well to the treatment, and after his third injection he had regained 90 per cent of his vision.

Liu gave Kong one more round of laser to ensure prolonged results.

With Kong's disciplined management of his blood sugar, the slight swelling in his left-eye macula also subsided. He continues to see Liu every three to four months for a check-up in case of a relapse.

Liu recommends that patients who are diagnosed with diabetes undergo tests to check for signs of macular edema. Early detection can save your sight.