Müller's muscle-conjunctival resection (MMCR) is an effective method of ptosis repair in which Müller's muscle is shortened with the aid of a clamp from the underside of the eyelid. Phenylephrine 2.5% or 10% is often used to determine if a patient will be a good candidate for this procedure. In this retrospective study, researchers analyzed 80 patients who underwent 131 MMCR procedures for correction of upper eyelid ptosis.
During the initial evaluation, phenylephrine 10% was instilled in the inferior cul de sac of the eyes with a ptotic eyelid. Planned surgery was based in the amount correction needed, with 4mm resection equating to 1mm of correction of ptosis. Only patients with levator function greater than 10 mm were included, and exclusion criteria included no response to phenylephrine, ocular surface disease, and superiorly placed glaucoma blebs.
Overall ptosis improved on average 1.6mm. Good eyelid symmetry was also achieved in 81 percent of cases (1mm of asymmetry or less between both sides). In unilateral cases asymmetry improved significantly from a mean of 1.6mm difference preoperatively to 0.16mm postoperatively.
Phenylephrine 10% caused an elevation of 0.7mm on average compared to 1.6mm mean change in eyelid height after surgery. Phenylephrine underestimated ptosis correction by 0.56mm on average. However, unilateral cases had less discrepancy, in which final eyelid height was underestimated by a mean of 0.35mm.
This study adds to the body of literature which demonstrates good efficacy with the Müller's muscle-conjunctival resection technique for ptosis repair. However it also demonstrates that MMCR is quite effective in unilateral cases, restoring symmetry to a high degree. However, phenylephrine which was used to screen patients for effect of surgical repair was not very good at predicting final eyelid height. In particular, the average elevation with phenylephrine was 0.7mm which may approach the definition of no effect on elevation at all.
Limitations of this study include its retrospective nature. Furthermore some patients underwent concomitant blepharoplasty and these were not analyzed separately. Also in unilateral cases, eyelid height changes on the unoperated eye were not analyzed, which may give a better idea as to why good symmetry was obtained in unilateral cases versus bilateral cases. Perhaps in unilateral cases, elevation of the ptotic eyelid was accompanied with drop of the contralateral side to a symmetric middle level.
In conclusion MMCR is effective in elevation of a ptotic eyelid, but phenylephrine is not very useful at predicting post-operative results of the MMCR technique.