A THREE-YEAR-OLD girl who travelled to Japan for brain surgery - thanks to the generosity of Post readers - is back in Hong Kong after undergoing a successful 10-hour operation. Yau Tsz-ying returned from Nagoya on Tuesday and is said to be well on the road to recovery after receiving treatment for a life-threatening malformation of the blood vessels in her brain. But doctors say her condition will have to be carefully monitored during the next two years, while it will be some time before they can tell whether or not she has made a full recovery. Tsz-ying's neuro-surgeon at Tuen Mun Hospital, Dr Fong To-sang, said: ''She looks as though nothing has happened to her and she is running around like any normal, healthy little girl. ''As far we can tell the operation was a success, although it is too early to say whether she will fully recover.'' The treatment involved hours of brain scans to pinpoint the problem areas, and the use of a gamma knife to direct a precise beam of radiation on to the malformed blood vessels - a technique not available in Hong Kong. The money raised was almost three times as much as the amount needed to pay for medical costs and accommodation. The remaining money will be used within the neuro-surgery department of Tuen Mun Hospital. The girl's parents thanked everyone involved for their help. ''We want to pass on our deepest thanks to the readers and Cathay Pacific,'' Yau Lau Mo-kit said. ''It means our daughter has the chance of a long and healthy life ahead of her,'' she said. Tsz-ying's parents and Dr Fok Kam-fuk from Tuen Mun Hospital were at her side throughout the ordeal after Post readers donated $300,000 to send them to Japan and the Cathay Pacific Charitable Travel Fund provided four return air tickets. Dr Fok said: ''The risks involved in the operation were quite minimal because the radiation beam is very precise but some of the malformed blood vessels may have been left behind.'' Tsz-ying now faces two years of drug therapy to control potential convulsions and a regular series of brain scans and studies so doctors can monitor her progress. Despite this, Dr Fok said she could expect to live a normal life.