eye·patch
Noun: A patch worn to protect an injured eye
Due to the contract over Ciel’s right eye, his vision is impaired. The mark is said to have been burned onto the eye, which would realistically effect it’s functioning ability. He could very well be considered half blind. The patch is worn to avoid questions, but wearing it all the time strengthens the eye that’s being used and weakens the one that isn’t. By patching one eye, the other eye is forced to function double, causing vision to be enhanced in one eye and lowered in the other. If Ciel isn’t totally blind in his right eye from the contract, the patch he wears has effected his vision anyway.
