Well it looks like your cycle is in good shape. This disease is usually caused by fish stress and poor water quality. Can you please provide some more info: http://www.bettafish.com/showthread.php?t=49233
I just want to make sure we don't miss anything.
Most eye infections are gram positive in nature so I would use an antibiotic like Kanaplex. It is the best available but it can be hard to find so if you can't find it I would try Maracyn Plus (this is not the same as Maracyn or Maracyn II) and if you can't find that Furan 2. I would also get some epsom salts from your local pharmacy or the pharmacy section of your grocery store. They must be pure magnesium sulfate with no other additives - check the ingredients label as this is extremely important. Predissolve them in some water and add them starting at a concentration of 1/4 tsp per gallon of tank water. Increase this up to 1 tsp per gallon of tank water. I would treat for two weeks.
It would be idea to treat in a hospital tank or to get a 1-2 gallon acrylic critter keeper or bowl of some kind, fill half full with water and treat floating in the larger tank to keep it warm. You can treat in the tank itself, however the antibiotics may crash your cycle.