Surgical outcome of Modified Nishida's procedure in monocular elevation deficiency

Purpose: Monocular Elevation Deficiency (MED) is characterized by limited ability to elevate the affected eye in any gaze position, while maintaining normal duction in all other gazes. The type of surgeries described in MED include Knapp's surgery, vertical muscle recession and resection, contralateral superior rectus recession. Recently, the Nishida's procedure has also been explored as a treatment for isolated cases of MED. Hence, we conducted this study to evaluate the surgical outcome of Modified Nishida's procedure in cases of MED in a series of 15 patients. Methods: This prospective interventional study was performed on 15 patients with MED attending the Strabismus Clinic and outpatient department of our tertiary care centre over a period of 1 year from October 2023 to October 2024. In this study, 15 patients of age more than 13 years with Type 2 Congenital MED with negative forced duction test for inferior rectus, hypotropia more than 10 prism diopters and no horizontal deviation were included. Patients with previous history of strabismus surgery or with bleeding diathesis were excluded. Preoperatively, ocular deviation was measured using vertical prisms in terms of prism diopters (PD). Elevation deficit was noted in all the patients on a scale of 0 to -4 with 0 indicating full rotation and -4 indicating severe limitation (not crossing midline). All patients underwent Modified Nishida's procedure following forced duction test for inferior rectus. Postoperatively, all the measurements were recorded at the end of first week, first month and the final follow up was done at the end of third month. Primary outcome included correction of vertical deviation at 3 months post Modified Nishida's procedure. Secondary outcome included assessment of elevation deficit. Results: The mean age of the patients was 23.33 ± 15.73 years. There was statistically significant improvement in mean hypotropia from preoperative measurement of vertical deviation of 28.67 ± 9.904 PD to 7.60 ± 10.176 PD (p < 0.001) at the final follow up. There was statistically significant improvement in elevation deficit ranging from mean value of -3.47 ± 0.74 at baseline to -2.73 ± 0.70 postoperatively at final follow up (p < 0.01). Conclusion: The study demonstrated that the Modified Nishida's procedure is effective in managing MED in terms of improvement of vertical deviation and elevation deficit.