Sometimes, tears are not enough

About 20 to 30 percent of Chinese suffer from dry eye disease, which means the eyes do not produce enough tears, causing a burning sensation and other discomfort.

Dry eye disease affects about 15 percent of Americans over 48, 29 percent of people in the UK and 20 percent for Indians in their 30s.

It has many causes like age, long-term exposure to computers and smartphone screens, medicine, certain refractive eye surgery, air pollution and kitchen smoke, medical experts said over the weekend.

The discomfort usually increases in winter because of the dry weather and use of central heating.

 “It is important to look for professional treatment instead of just buying eye drops online,” said Dr Yao Ke, director of Chinese Medical Association's ophthalmology branch. 

Blinking more, increasing humidity indoors and use of artificial tears can solve most dry eye conditions.

Some novel eye drops were developed recently. Artificial tears, as a conventional therapy for dry eye disease, just provides moisture, while the new generation of eye drops like those with diquafosol sodium can promote secretion of tears.