There are quite a few good vets in HK, but I guess that could be seen as being a little subjective
As far as opthalmologists goes, there are a few vets that have a special interest in opthalmology, but there is no registered specialist living in HK. However, once or twice a year we have a registered opthalomolgy specialist come from Australia and do a bit of touring in HK. I think most vets would be capable of seeing your Lab, or referring him to someone suitable.
Hope this helps a little...
Vet in HK