I believe that the standards required in HK, and alot of the world, are vision correction not greater than 3 diopters. If you are close to this I can see why a company might pass you over, as you might well fail your medical in the future.
In Australia they changed this requirement about 10 years ago. Now all you need is to be able to see 6/9 with each eye and 6/6 with both eyes together WITH your glasses or contacts on.
I have read on the ICAO website that they will be recommending to their member states that they all change to this new criteria in about Nov 2001. Whether or not HK or the UK change their medical standards though is not known as the ICAO standards are minimums - the member states can still require stricter standards.