The lazy eye has an inertia to move due to underlying muscle involved which is really lazy to work, meaning to contract in order to brings about opening of the upper eyelid. The muscle involved is the levator palpepral labi superioris. Its contraction brings about shortening of this muscle, hence, lifting of the upper eyelids.
As mentioned, the main immediate causes of the lazy eye is due to the decreased activity of the muscle that opens and lifting the upper eyelids, the name of this particular muscle implicated is a specific one muscle called the levator palpepral labi superioris muscle. The muscle cannot contract as much as it should be to lift the upper eyelid fully. The muscle fails to shorten or contract adequately when the upper eyelid opens. What exactly causes or the etiology causing the inactivity of this muscle is not known.
This muscle is generally longer than the normal muscle. So, during the correction surgery, it needs to shortened such that in a fully open eyelid, the muscle length is the same. When after this correction, there is some difficulty of closing the corrected eyelid completely as this muscle has been shortened. The correction is by way of excising an exact length of the muscle and re attached back. Another way is to do placation of the muscle along its length.
However, as the muscle starts to exercise, slowly the eye can starts to fully close again.
Laxy eye correction, completed surgery, doing checking on the balances