I would advise you to go to polyclinic and tell them the problem... get them to refer you to KK. It would be much cheaper this way....
My boy failed the eye test during his 4 year old checkup at the polyclinic and was referred to KK for further test. Each time the payment is less then $50 and is like half a year or 1 year kind of routine check. He have very high astigmatism and no myopia.... now he's 7 years old and KK say he no longer need to go hospital check and can just go to the normal optician as he is old enough to concentrate and communicate.