Long-term outcomes of inferior rectus recession with conjunctival recession in congenital monocular elevation deficiency: a case series

Introduction: Monocular elevation deficiency (MED) can be congenital and acquired. The underlying etiology usually guides the surgical management of MED. In cases with tight inferior rectus (IR) on forced ductus test, IR recession is preferred, and in cases with Superior rectus palsy, vertical transposition of horizontal recti (Knapp's Procedure) is the treatment of choice. The purpose of this case series is to report the long-term outcomes of inferior rectus recession with conjunctival recession in treating congenital monocular elevation deficiency (MED). Methods: It included 10 patients of congenital MED who underwent inferior rectus recession (IRR) with conjunctival recession (CR) from 2019 to 2021 with a minimum follow-up of 2 years. They all underwent complete pre-operative orthoptic evaluation, including the prism bar cover test (PBCT), and had primary position vertical deviation only. A forced duction test (FDT) was done, and 6 mm of IRR with CR was performed on all, irrespective of the FDT findings. Results: The mean age of the participants was 18 years; the mean pre-operative vertical deviation was 33 prism diopter (PD), and horizontal alignment was within 8 PD. FDT for IR was positive in 5 and negative in 5 patients. Orthophoria was achieved in 7 patients following 6 mm of IRR with CR, with a mean post-op vertical deviation of 8.9 (p-value 0.01). (mean post-op vertical correction achieved was 24.1 PD), while 2 needed Knapp's procedure and 1 needed SR recession in the fellow eye. We also noticed an improvement in elevation from preop -3.4 to mean postop -1.7 (p-value 0.0001) after IRR. This alignment was maintained till 2 years of follow-up. Discussion: This case series shows that 6 mm IRR-CR is an effective and reliable procedure for correcting vertical deviations up to 24 PD in cases of congenital MED regardless of FDT findings.