they are huge indeed... Monogenean flatworm parasites. Quite commonly on the eyes (as with your image here... often ascribed to Neobenedenia). [folks... do note the opaque "fluke" like critters on the eyes, behind the pectorals... mid flank, etc in the first picture]
They are quite easy to dip off the fish (they usually respond to copper, though I dont often use or recommend it... and they respond to formalin and even just extended FW dips).
The greater issue here is that while it will be easy to purge them from the trigger once pulled back to a QT tank... the display has now been infected. You may have more than a few fish catshes to make. Do see the big thread archived here at RC on "catching fish in a display" (many easy tips there)
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"Genus Neobenedenia, which is much larger and lives on the skin of many tropical marine species, causing problematic disease in marine aquaria."
http://en.wikipedia.org/wiki/Monogenea
But please do see the fish path refs of Noga, Post, Untergasser or Blasiola&Gratzek for more hobby specific info and treatments.