Need pictures to actually see what is wrong with the eye. Without seeing the fish and how it swims, I am unwilling to guess. It's like going to a doctor and saying "Doc, I have a sore on my leg and it isn't healing". The doctor asks to look at it and you say no. The doctor can't identify the issue if they can't see it.
A picture showing the main tank can also give us an idea of how it's set up and whether anything can be changed in it so the fish can go back in there. However, if the fish is blind, it should not be housed with anything that can pick on it and a pair of convict cichlids will probably kill it.
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Don't give fish salt baths. Every time you chase and catch the fish, you stress it out. Lifting the fish out of water can cause minor scratches and abrasions that can lead to infections. If you want to use salt, add salt to the tank and leave it in there for 2 weeks. The salt will treat the fish and kill anything in the water that might be infecting the fish.
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SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres (5 gallons) of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.
Keep the salt level like this for 2 weeks. If there's no improvement after 1 week, then stop using salt.
The salt will not affect the beneficial filter bacteria, fish, plants, shrimp or snails.
After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.
If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
When you first add salt, add the salt to a small bucket (2 litres/ 1/2 gallon) of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.