Optic nerve sheath fenestration for salvaging acutely threatened vision in Idiopathic Intracranial Hypertension - A two-year completed follow up

OBJECTIVES: To determine the efficacy and safety of Optic Nerve Sheath Fenestration (ONSF) for salvaging acutely threatened vision in patients of Idiopathic Intracranial Hypertension (IIH). METHODS: This retrospective, interventional case series study was performed at Institute of Ophthalmology Mayo Hospital Lahore from September 2017 to September 2019. Nine patients diagnosed with Idiopathic Intracranial Hypertension as per Modified Dandy Criteria, underwent medial trans-conjunctival ONSF. Pre-operative and 1(st) day, 1(st) week, 1(st) month, 1(st) year, and 2(nd) year postoperative best-corrected logMAR visual acuities (BCVA) were recorded. Mean BCVA were calculated and compared using paired t-test. P-value <0.05 was taken as significant. RESULTS: All nine patients were female with a mean age of 24 years. The average best-corrected pre-operative logMAR visual acuity (BCVA) in the better eye was 0.5 ± 0.28 and in the worse eye was 1.0 ± 0.57. After the worse eye ONSF, at 1(st) week mean BCVA in better eyes was 0.27 ± 0.32 (p-value=0.001), while it was 0.43 ± 0.63 (p-value=0.006) in the worse eyes. At 2nd year follow-up after optic nerve sheath fenestration mean BCVA in better eyes was 0.30 ± 0.30 (p-value=0.002) and in worse eyes was 0.44 ± 0.63 (p-value=0.007). Four patients (44.4%) had a subconjunctival hemorrhage, two patients (22.2%) had binocular diplopia, one patient (11.1%) pre-septal cellulitis, and one patient (11.1%) had no improvement in vision because of pre-operative secondary optic atrophy. All patients had unilateral fenestration and bilateral improvement, six patients (66.67%) reported improvement in headache and successful tapering of medical therapy. CONCLUSION: Optic nerve sheath fenestration is effective as well as a safe surgical procedure to salvage acutely threatened vision in patients of Idiopathic Intracranial Hypertension on maximal medical treatment.