More than 22 million Chinese people suffer from glaucoma, the second leading cause of blindness worldwide. However, at least 80 percent of the patients on the mainland may be unaware they have the condition, warns an epidemiology survey.

Among 5,300 respondents to the online survey by the Chinese Medical Association (CMA), nearly 74 percent had no idea about the disease, which experts call the "silent thief of sight".

Less than 20 percent of Chinese suffering from glaucoma get timely diagnosis and treatment, and about 55 percent of them go irreversibly blind because of it, says Professor Zhao Kanxing, who heads CMA's ophthalmology society.

"Regular checkups which facilitate early detection and treatment, are the best ways to protect sight," he notes.

Home to a quarter of the world's glaucoma patients, China has few people with regular dilated eye exams - the most effective way to detect glaucoma - until partial vision loss has occurred, says Ge Jian, CMA's deputy director, citing the survey results.

"I never consider eye problems as that serious and usually skip that part during my annual health checkup," says a 64-year-old retired middle-school teacher, surnamed Wu, in Beijing.

Ge says it is precisely this age group that is at highest risk of contracting the disease. Other vulnerable groups include family members of those already diagnosed with glaucoma, diabetics, and people who are severely nearsighted.

But Ge points out that everyone is at risk of glaucoma, from babies to old people. There is a one-in-10,000 risk of a baby being born with glaucoma.

Veteran eye doctor Wang Ningli, of Beijing's Tongren Hospital, suggests people older than 40 and frequent computer users receive glaucoma screening every two years.

People using computers for nine hours or more per day are twice as likely to develop glaucoma, he says.

"It takes only five minutes and costs 20 yuan ($3.06) to be screened," he says.

The survey also found that more than half of those polled didn't know that glaucoma required lifelong medication to halt further vision loss.

As glaucoma is a chronic disease, once diagnosed, it has to be monitored and treated for life, Wang says.

He adds that to improve intervention efforts, there needs to be more education about the disease, particularly at the grassroots level, beginning with medical institutions and community clinics, which would help facilitate better public access to screening services and improve detection.

CMA has organized training for grassroots-level doctors to diagnose and treat the disease, Wang says.