was sitting at home - nothing much to do so looked on the net. heres some bits and pieces I read, have you considered flukes as apparently they can cause excess mucus and muck up the eyes. Have a look below.
Whitish Film over the eye of the tropical fish.
This could be because of poor water quality, chlorine poisoning or eye fluke.For poor water quality you have to change the water. For chlorine poisoning you should condition tap water before using it. For eye fluke please use proper medication.
Dull color (mucus), detached skin or fraying of the fin could be Mucus Hyperproduction. This is caused by Slime disease (parasite, meds), poor water conditioners (high nitrogenous waste), fukes and stress.
A whitish film appears over the eye of the fish. This occurs due to poor water quality or poisoning (chlorine) or Eye Fluke.
and have a look at following site
http://badmanstropicalfish.com