Optic Nerve Sheath Fenestration

Surgery to create openings in the optic nerve sheath to reduce pressure and protect vision in IIH.

Optic nerve sheath fenestration (ONSF) is a surgery that creates small windows (fenestrations) in the covering of the optic nerve. This allows cerebrospinal fluid to drain, reducing pressure on the nerve and protecting vision.

Key Takeaways

Protects vision in IIH and papilledema
Reduces pressure around optic nerve
Done for vision-threatening disease
Doesn't treat headaches (usually)
Alternative to shunting

When It's Done

Rapid or severe vision loss from papilledema
Medical treatment not working fast enough
Vision-threatening IIH
May be done on one or both sides

How It Works

The optic nerve is surrounded by a sheath containing CSF. When intracranial pressure is high, this pressure is transmitted to the nerve. Fenestration:

Creates drainage openings
Reduces pressure locally around nerve
Protects optic nerve from further damage

The Procedure

Before Surgery

Complete eye examination
Visual field testing baseline
Discuss risks and benefits

During Surgery

General or local anesthesia
Incision inside eyelid or lateral approach
Access to optic nerve sheath
Small cuts made in sheath
Takes 1-2 hours

After Surgery

Eye may be patched initially
Antibiotic drops/ointment
Avoid straining
Usually outpatient

Outcomes

What It Helps

Stabilizes or improves vision
Protects optic nerve

What It Doesn't Help

Headaches (usually)
Papilledema in other eye (sometimes)

Risks

Double vision (temporary or permanent)
Vision loss (rare)
Pupil abnormality
Bleeding
Infection

Compared to Shunting

ONSF: treats eyes directly, not headaches
Shunt: treats entire system, helps headaches
Sometimes both needed

Medically Reviewed Content

This article meets our editorial standards

Written by:: Hashemi Eye Care Medical Team
Medically reviewed by:: Board-Certified Neuro-Ophthalmologist (MD, Neuro-Ophthalmology)
Last reviewed:: January 30, 2025

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