Here we go again....it seems like Leo is never healthy :(
Currently I have him in a 1.5 gallon tank that usually houses my delta tail, Toby (Toby is now in Leo's space in the 10 gallon tank). I'm using the 1.5 gallon as a hospital tank right now, since it's easier to do water changes & treat, and doesn't have any gravel in it.
I also added in the responses for my 10 gallon tank.
**Also, I can't really get a good picture of him, because he is so dark blue that he looks black and the eye doesn't show up in any pictures I take...
I did some quick research before treating him and read that it may be a type of fungal infection...so I moved him from the 10 gallon (where it is 82*) into the 1.5 gallon (which is 78*), since I read that if it's a fungal infection, warmer water ill not help to get rid of it. I have also begun treating him with 1 teaspoon of dissolved AQ salt. But I'd really appreciate other people's input/thoughts as to what it might be. My little guy has been through a lot and the last thing I want is for his eye to become damaged!!
Housing
What size is your tank?
1.5 gallons (he is usually in a divided 10 gallon)
What temperature is your tank?
1.5 gallon: 78*
10 gallon: 82*
Does your tank have a filter?
1.5 gallon: no
10 gallon: yes
Does your tank have an air stone or other type of aeration?
1.5 gallon: no
10 gallon: no
Is your tank heated?
1.5 gallon: yes
10 gallon: yes
What tank mates does your betta fish live with?
usually lives in a 3-way divided 10 gallon tank (other males in tank are a double tail and a half-giant PK)
Food
What type of food do you feed your betta fish?
Omega One Betta Buffet Pellets
Frozen Brine Shrimp (as a treat, only a small pinch once a week)
How often do you feed your betta fish?
1 or 2 pellets every other day (he tends to bloat easily)
Maintenance
How often do you perform a water change?
10 gallon: 30% water change every 3 days (since there are 3 males currently living in it)
1.5 gallon: 100% change every 2-3 days
What percentage of the water do you change when you perform a water change?
see above
What type of additives do you add to the water when you perform a water change?
1.5 gallon: API Tap Water Conditioner (removes chlorine, chloramine & heavy metals)
10 gallon: API Tap Water Conditioner & Prime (to control the ammonia that is already present in my tap water)
Water Parameters:
Have you tested your water? If so, what are the following parameters?
I don't have a test kit..I only have strips but they are not very reliable so I don't use them too often. I can't afford a liquid test kit right now (not even one just for ammonia). But I do know the ammonia & pH parameters.
Ammonia:
0.5 ppm (this is already present in the tap water when it comes out of the faucet, so I use Prime to help neutralize it. The water where I live isn't too good.)
Nitrite:
N/A
Nitrate:
N/A
pH:
~8.5 (we have very soft, very alkaline water where I live..it's really weird)
Hardness:
N/A
Alkalinity:
N/A
Symptoms and Treatment
How has your betta fish's appearance changed?
His right eye is suddenly very cloudy. Like it has a milky/opaque, light blue cloud over it.
How has your betta fish's behavior changed?
It hasn't changed as far as I can tell. I dropped in a couple of pellets on the side where the cloudy eye is and it did take him longer than usual to notice them.
When did you start noticing the symptoms?
Tonight, at around 12:30 AM (I don't know if it was cloudy earlier today, I didn't really have time to check in on my fish until tonight)
Have you started treating your fish? If so, how?
Moved him from the divided 10 gallon into a 1.5 gallon tank, at a lower temperature of 78*. When filling the tank up with new water after water change, added about 1 teaspoon of dissolved AQ salt.
Does your fish have any history of being ill?
Where do I begin? He has been through ammonia burns, salt burns, tail biting/rot (I think it was a combination but I don't know for sure...his tail was just a stub for a really long time). In November he contracted velvet and ended up basically chewing off his ventral fins and scratching his head so hard on the heater that he had big white scars where the scales were missing. He finally recovered in January and was then transported into the big tank when he was fully healed and I was positive he didn't have the parasite anymore (after several alternating rounds of Maracide & AQ salt treatments). And now this...I hope it isn't anything serious 
How old is your fish (approximately)?
I got him in September, so it is probably close to a year old, give or take a couple of months.