The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
One or both eyes? If its one eye, then its just an injury. If its both eyes, it may be popeye. Generally it will not spread to other fish and cannot spread to inverts.
What is the situation, new fish? How long in the system?
If its one eye, its not popeye. Definately an injury. Keep water quality high and lace his food with a vitamin supplement like selcon and it should clear up on its own.
If it doesn't improve in a few days, you could move him to a qt tank and treat with antibiotics and/or epsom salt.
HTH
Best first step is a few good sized water changes over the next few days with well aged and aerated SW. This will most times reduce the DOC feeding any bacteria causing the swelling to subside.