Association between pre-operative fluid cuff and visual outcomes after optic nerve sheath fenestration

Abstract

Purpose : Optic nerve sheath fenestration (ONSF) is a demonstrable way to alleviate acute vision loss from papilledema in idiopathic intracranial hypertension, though few data exist to identify which patients may respond best to surgery. We performed a retrospective cohort study on individuals who underwent ONSF to assess if pre-operative fluid cuff size on MRI was associated with changes in best corrected visual acuity (BCVA) and Humphrey visual field 24-2 (HVF) post-operatively.

Methods : Records of 27 patients (ages 8 and 61 years) who underwent ONSF at the Children’s Hospital of Philadelphia and the Hospital of Pennsylvania between 9/8/09 and 4/29/22 were included in the study. Inclusion required a preoperative MRI brain or orbits within 1 month of ONSF and minimum 3 months of postoperative clinical follow-up. For patients who underwent HVF at baseline and follow-up, MD of each eye was recorded. ITK-SNAP was used to quantify the ratio between optic nerve and surrounding fluid cuff volume on axial MRI starting 5 mm posterior to the globe and extending 9 mm posteriorly or until anatomic borders became unclear using T2 fat suppressed sequences if available, and T1 sequences if unavailable. Generalized estimated equations were used to evaluate changes of BCVA and HVF MD between pre and post-operative visits.

Results : Mean preoperative HVF MD was -21.60 ± 9.88 db, which improved to -14.60 ± 8.18 db (p < 0.05) in operated eyes tested (N=11) at last follow-up. Mean preoperative logMAR BCVA was 0.73 (median 0.54) and 0.83 (median 0.18, p=0.64) at last follow-up in 31 operated eyes. 71% of the eyes had an improvement in BCVA at 3 months post-op, with 42% of eyes improving two or more lines. 73% of the eyes had an improvement in MD of visual field at 3 months post-op, with 64% of eyes having a 10-20 db improvement. Mean volumetric preoperative fluid cuff to optic nerve ratio was 0.62 ± 0.09, which was not statistically significantly associated with BCVA (p = 0.28) or MD of visual field (p = 0.91) at 3 months post-op in the operated eye.

Conclusions : ITK-SNAP was used in a novel manner to quantify fluid cuff. Fluid cuff to optic nerve ratio was not associated with post-operative MD on HVF or BCVA. There was a significant improvement of HVF as measured by MD after ONSF in tested patients. Post-operative BCVA was not statistically improved, though over 70% of patients had improvement at 3 months.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.