Influence of upper and temporal transconjunctival sclerocorneal incision on marginal reflex distance after cataract surgery

BACKGROUND: Ptosis incidence following cataract surgery is reduced with a recently developed phacoemulsification technique using a small incision. However, it remains uncertain whether an upper transconjunctival sclerocorneal incision can cause minor blepharoptosis. In the present prospective study, patients underwent cataract surgery with either an upper or temporal 2.4-mm transconjunctival sclerocorneal incision. We measured the marginal reflex distance 1 (MRD1) preoperatively and postoperatively, and compared these measurements between the two different incision types. Further we explored the risk factors of the postoperative MRD1 reduction. METHODS: The study population included patients who underwent cataract surgery on both eyes at Aichi Medical University between October 2013 and September 2015. In each patient, one eye was operated using an upper 2.4-mm transconjunctival sclerocorneal incision, and the other with a temporal incision. We prespecified that an MRD1 difference of ≥0.5 mm between the pre- and post-surgical measurements indicated postoperative ptosis, which was a strict criterion. MRD1 was measured using digital photography, and we calculated the difference between the preoperative and postoperative MRD1 values. This change in MRD1 was compared between the groups with different incision locations. The change in MRD1 was analyzed by using the multivariate regression model including incision position (temporal or upper), preoperative MRD1, and preoperative distance between medial and lateral canthi. RESULTS: We assessed data from a total of 34 patients. The mean change in MRD1 from pre-operation to post-operation measurements was −0.26 ± 0.93 with the temporal incision and −0.24 ± 0.86 with the upper incision. The mean difference in the change in MRD1 between the different two incision types was −0.02, with a 95 % CI of −0.24 to 0.20, establishing equivalence between these incision types. The multivariate regression analysis showed that the preoperative MRD1 was significantly associated with the reduction of MRD1 after surgery (p = 0.034). CONCLUSIONS: Cataract surgery using upper and temporal 2.4-mm transconjunctival sclerocorneal incisions are clinically equivalent with regards to change in MRD1, and neither incision type caused critical postoperative ptosis. The longer preoperative MRD1 was significantly associated with the reduction of MRD1 after surgery. TRIAL REGISTRATION: Current Controlled Trials UMIN000022310. Retrospectively registered 14 May 2016. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12886-016-0286-1) contains supplementary material, which is available to authorized users.