Postoperative Vision Loss

Postoperative vision loss (POVL) is loss of vision in one or both eyes after surgery under anaesthesia, noticed on waking or within 1 to 2 days. It is rare and devastating.

Epidemiology. Incidence is about 1 in 60,000 to 1 in 125,000 non-ocular operations, higher after spinal fusion (about 1 in 1,100 to 1 in 3,000) and cardiac surgery (about 1 in 1,000 to 1 in 10,000 and up to 0.1%).

Causes. Ischaemic optic neuropathy (posterior or anterior), central retinal artery occlusion (pressure on the eye in prone position), cortical blindness (posterior circulation hypoperfusion), central retinal vein occlusion, corneal abrasion, acute glaucoma and pituitary apoplexy.

Risk factors. Prolonged prone surgery (over 6 hours), large blood loss (over 1 L), hypotension, anaemia, large crystalloid volumes, male sex, obesity, head down position, Wilson frame, diabetes, hypertension, vasculopathy, and smoking.

Pathophysiology.

The optic nerve has watershed blood supply, and hypotension, anaemia, venous congestion and raised intraocular pressure can reduce perfusion. Direct eye compression raises intraocular pressure and obstructs the central retinal artery.

Painless visual loss (blurring, field defect, total loss) noted on waking or within 48 hours, relative afferent pupillary defect, pale or swollen optic disc, facial and periorbital oedema (prone position), ophthalmoplegia, and corneal clouding.

Red flags.

• Eye pain or red eye (acute glaucoma).
• Neurological deficit (cortical infarct).
• Proptosis or headache.
• Bilateral visual loss.

Urgent ophthalmology review, visual acuity, pupils, visual fields and fundoscopy (disc swelling in anterior ischaemic optic neuropathy, normal disc early in posterior; retinal whitening with cherry red spot in artery occlusion). MRI brain and orbits with diffusion (cortical or optic nerve infarct, pituitary apoplexy). Check haemoglobin, glucose, inflammatory markers and blood pressure.

Differential diagnosis.

• Anterior or posterior ischaemic optic neuropathy.
• Central retinal artery occlusion.
• Cortical blindness.
• Corneal abrasion.
• Acute angle closure glaucoma.
• Pituitary apoplexy.
• Giant cell arteritis.

This is an emergency. Correct anaemia (transfuse to haemoglobin 80 to 100 g/L if ischaemia is suspected), restore mean arterial pressure at 65 mmHg or more (and to baseline in hypertension), give 100% oxygen, and elevate the head over heart level only when it does not impair cerebral perfusion; keep head at or over heart level.

• Acetazolamide (raised intraocular pressure or central retinal artery occlusion): 500 mg IV once, then 250 mg orally every 6 hours; maximum 1 g daily; monitor potassium, bicarbonate and renal function; avoid in sulphonamide allergy and severe renal impairment.
• Timolol 0.5% eye drops, one drop twice daily, for raised intraocular pressure; avoid in asthma and bradycardia.
• Mannitol: 0.5 to 1 g/kg IV over 30 minutes for acute glaucoma; maximum 2 g/kg; monitor osmolality, sodium and renal function; avoid in anuria and heart failure.
• Steroids and other agents for ischaemic optic neuropathy have no proven benefit.

Central retinal artery occlusion: ocular massage, lowering intraocular pressure and urgent ophthalmology or stroke team review within hours (thrombolysis is considered within 4.5 hours in selected centres).

Prevention. In high risk prone spine surgery, keep the head neutral and at or over heart level, free the eyes from pressure (use pin fixation or a pillow with eye check every 20 minutes), maintain blood pressure near baseline, limit crystalloid, correct anaemia and consider staging the procedure.

Monitoring. Visual acuity, pupils and fundus examination daily, and blood pressure and haemoglobin.

Referral and escalation. Ophthalmology emergency review, neurology and neuroradiology. Disclosure and reporting.