Shedding some light on physical appearance of a Palpebrosa

I am no expert on bird identification. The below photos wasn't commented by me, but some pointers I received from a fellow hobbyist. There was this guy who says that he supplies the "true" Oriental White Eye. So, how to know the difference?
Some say by the voice. But identification of birds through voice is a very specialised skill. I, for one would be quite blur on this, so I would leave it to the experts to thrash it out. But for those who may take an interest on physical difference of sub-species of the Zosterops......