Surgical Management of Primary Inferior Oblique Muscle Overaction: A Subgroup-Specific Surgical Approach.

OBJECTIVES: The aim of this research was to assess the surgical results of recession and myectomy procedures in a subgroup of patients who had primary inferior oblique muscle overaction. METHODS: The records of 94 patients who had been treated due to primary inferior oblique muscle overaction were retrospectively analyzed. The patients were classified into 2 groups according to the severity of the inferior oblique hyperfunction. Recession was performed for patients with a low grade (+1 or +2) inferior oblique hyperfunction, and patients with high grade (+3 or +4) hyperfunction underwent myectomy surgery. Patients demonstrating a horizontal misalignment underwent conventional horizontal muscle surgery along with an inferior oblique weakening procedure. RESULTS: A total of 134 eyes fulfilled the inclusion criteria. Recession was performed in 95 eyes and myectomy in 39. Surgical success was obtained in 96.8% of the eyes that underwent recession and 97.4% of the eyes that underwent myectomy. Residual inferior oblique hyperfunction was observed in 3 eyes after recession and in 1 eye after myectomy. After surgery, about one-quarter of the patients with unilateral inferior oblique overaction subsequently developed a contralateral inferior oblique overaction. CONCLUSION: The results of this study demonstrated that both recession and myectomy procedures are effective for treating primary inferior oblique hyperfunction with minimal complications when applied in the appropriate patient.