To assess the change in levator function (LF) after ptosis repair in patients with unilateral myogenic (MP) and aponeurotic (AP) ptosis, compare the success rates, and analyze factors affecting them.

Patients of >5 years old were included from June 2015 to April 2017. Other types of ptosis, associated strabismus and previous eyelid surgery were excluded. Eyelid examination and photography were performed before and at least 6 months after ptosis repair. Success of ptosis repair was defined as MRD1 equal or within 0.5 mm of the other side. All procedures (levator resection) were performed by or under supervision of one oculo-facial plastic surgeon.

Seventy-eight cases with MP (58) and AP (20) with mean age of 19.2 (MP) and 49.5 (AP) years and median follow up of 10 months were included. Success of ptosis repair was observed in 84.5% (49/58) of MP and 100%. Re-operation for under-correction was performed in 9 cases with MP. Finally, within 0.5 mm of over-correction was observed in 2 cases (MP: 1, AP:1) and under-correction in 5 cases (MP: 4, AP: 1). Mean LF was significantly (P=0.001) increased from 5.9 to 7.3 mm in MP group and from 9.5 to 11.3 mm in the AP group. However, it did not change in 17.2% (10/58) cases with MP and 25% (5/20) in AP. Increasing age was the only significant factor increasing the success of ptosis repair in MP (P=0.02) in regression analysis.

LF increases significantly after levator resection in majority of cases with MP and AP which should be considered for re-operation planning. The higher the mean age the more the success rate of levator resection in cases with MP.