Big Eye Betta 911

Question
I have just noticed today that my male beta has a VERY big eye (only one, not both) and is "hazed" over.  It does not appear to be anything growing on the outside.  I have had him for about 1.5 years, and he has been in his current tank for about one year.  He is only slightly less active than normal, not quite lethargic, and is still eating.  When i just fed him i noticed what appeared to be him having trouble seeing out of the swollen eye.  I have already changed his water and am moving him to a warmer spot in the house. Is this fungal? Bacterial? if not sure... which would be more important to treat first?  p.s. If it helps... his "normal" eye is almost flush to his head, while the "big eye" is about the size of a food pellet. (my first thought was that he had a food pellet stuck to his head!!)

Answer
Sounds similar to cloudy eye. This usually occurs when a fish is exposed to poor water quality (toxic chemicals such as ammonia) for a prolong period of time. I recommend that you keep up on your water changes, twice a week for anything under one gallon, and once a week for tanks 2-5. Keep his temp between 75 and 85 degrees, and make sure you don't overfeed him. Fresh, clean, dechlorinated water is the key!

Either way, these diseases are caused by poor water quality, and medication is not always the first step. Prevention is the best defense against illness, and you must keep his water clean! It's better to keep him from getting sick in the first place, rather than letting conditions go bad and then trying to fix them.