Mayor Thomas M. Menino is scheduled to undergo surgery Wednesday to repair drooping eyelids, a medical condition that has slowly obscured his vision over the past decade and is most likely a consequence of age.

Menino will remain awake but sedated during an hourlong procedure to bolster tendons that control the upper eyelids. Gradually, the tendons have stretched and stopped working properly, leaving the mayor’s eyelids so low they cut across the middle of his pupil and obscure his sight.