Ptosis can be a disabling condition that interferes with the superior field of vision when the eyelid crosses or drops below the visual axis. The etiology of ptosis can be congenital, mechanical, myogenic, neurogenic, or traumatic. There are different ways to address this problem surgically, depending on the etiology.
In congenital ptosis, the levator muscle is infiltrated with fat and fibrosis and is basically non-functional, so the eyelid is most commonly suspended from the adjacent frontalis muscle using a sling of synthetic, cadaveric or autogenous material.
In the case of levator dehiscence, when the muscle is functioning properly, the two most common procedures are conjunctival-mullerectomies (CMMR) and levator advancements (LA).
On clinical evaluation, it is important to measure palpebral fissure height, levator function and marginal reflex distance. If the patient has good levator function, a CMMR or LA may be appropriate. Many will test the patient in clinic by putting one to two drops of phenylephrine underneath the ptotic lid to check whether Muller’s muscle responds and the lid elevates. If the lid responds, the patient is likely a good candidate for a CMMR. If the lid does not respond, some will proceed with a CMMR regardless, but many will resort to a LA.
Advantages of CMMR include the fact that the procedure is faster and is generally associated with less swelling and post-operative lagophthalmos. The disadvantage is that many have to be done under monitored anesthesia care since the eyelid has to be double everted. LA can be done under straight local anesthesia, but generally takes more time and is associated with more swelling.
Bottom line is that both procedures are effective and some prefer CMMR, some prefer LA. The end goal is the same — elevation of the drooping eyelid, and these results can be achieved with either.