What causes blindness in iguanas?

i work at a pet store and recentally we have found out one of the iguanas we have are blind and so i took it home and have been hand feeding it but it is really weak so im giginv it calcium but why would it be blind because about a month ago it was fine and then we noticed one of its eyes puffy and thne he lost vision it that one and then out of nowhere his other eye lost sight in it, so now he doesnt have one eye in the socket and the other one has a scab over it but is gray and blurry. do you thinnk he got in a fight with one of the other ones and that might be why or do you think he has a disease, if so what is the disease that is making him weak and blind, and more importantally what do i do to help it?