THE eyeball, with a diameter of only 24 millimetre and a weight of 45 grams, less than an egg, is the main channel by which we receive information. But short-sightedness, or myopia, still puzzles quite a lot of people.

　　A recent survey shows that one quarter of Chinese suffer from poor eyesight; in other words, about 33 per cent of the world's myopic people are Chinese.

　　Glasses are the most common method for correcting eyesight, but even advanced computer testing systems and very skillful optometrists can't prepare a completely-suitable pair of glasses because the eyes are such complicated optical systems.

　　In recent years, laser surgery has become a more effective way of improving eyesight, one which is painless, quick, accurate and with fewer complications.

　　There are currently three types of laser surgery available, PRK, LASIK and LASEK, which allow over 98 per cent of patients to recover quite good eyesight.

　　During PRK, doctors use a laser to cut away part of the cornea. This method is applied for myopia of a middle degree or below.

　　Patients with very poor eyesight are better suited to LASIK, while LASEK surgery, combining the advantages of other two, is perhaps the best method of all.

　　Laser surgery for treating myopia has been used in China for over 10 years and the cost is much cheaper than in most Western countries.

　　The author, Wu Liangcheng, is a doctor from Shanghai Eye Hospital