Vision loss after nonocular surgery is a devastating complication that is most often associated with:
Spine surgery (1)
Cardiac surgery (1)
Head and neck operations (1)
The most common diagnoses include:
Posterior ischemic optic neuropathy (PION)
Anterior ischemic optic neuropathy (AION)
Central retinal artery occlusion (CRAO)
Occipital infarct (cortical blindness)
Although a minority of patients recover some partial vision, the improvement is often clinically insignificant. In addition, there are no proven treatment options.
Epidemiology
Incidence
Depends on the type of surgery
Cardiac surgery: 8.64 cases/10,000 surgeries (2)
Spinal fusion: 3.09 cases/10,000 surgeries (2)
Appendectomy: 0.12 cases/10,000 surgeries (2)
Age range: 5–81 years
Male > female
Morbidity
Depends on the diagnosis
ION (anterior and posterior)
Usually bilateral, painless vision loss
Afferent pupil defect or nonreactive pupil
No light perception
Color vision is decreased or absent
CRAO
Unilateral vision loss
No light perception
Afferent pupil defect
After prone spine surgery, it is often associated with periorbital or eyelid edema, chemosis, proptosis, ptosis
Cortical blindness
Patients have reduced vision with normal pupil reaction, intact corneal reflexes, and normal eye movement.
Etiology/Risk Factors
Ischemic optic neuropathy (posterior): The etiology or cause of this complication is unknown but it is presumably a vascular injury caused by arterial hypoperfusion or possibly elevated venous pressures secondary to prone positioning and/or interstitial tissue edema.
Occurs most commonly in prone spine surgery of long duration (>6 hours) and large blood loss (>1 L).
Also occurs in cardiac surgery, head and neck surgery, but rarely in other types of surgery.
Other associated factors (not necessarily causative)
Hypotension
Anemia
Excessive fluid administration
Vasopressors
Elevated venous pressure
Ischemic optic neuropathy (anterior): The etiology is unknown, but like posterior ION, it is presumably a vascular injury caused by arterial hypoperfusion or possibly elevated venous pressure. Occurs most frequently after cardiac surgery but can also occur in prone spine and head and neck surgeries (3).
Central retinal artery occlusion: Emboli are the usual cause in cardiac surgery; whereas direct pressure on the globe causes this injury in the prone spine surgery.
Cortical blindness: The etiology is ischemia and infarction involving the occipital lobe of the brain (where the visual cortex is located). It is either due to emboli that occur secondary to manipulation of the great vessels during cardiac or vascular surgery, or from hypoperfusion secondary to hypotension. The parieto-occipital region of the brain is a watershed zone for the middle cerebral and posterior cerebral arteries, and may undergo infarction during periods of systemic hypotension or if emboli block blood supply. Neuronal cell death is imminent after approximately 6 minutes of halted blood circulation.
Risk factors (4)
Hypertension
Diabetes mellitus
Renal insufficiency
Smoking history
COPD
Peripheral vascular disease
Cardiac disease
Physiology/Pathophysiology
Normal anatomy of the optic nerve:
Contains myelinated axons that arise from the ganglion cells in the retina.
Nerve fibers traverse from (distal to proximal)
Head and ocular portions traverse the sclera
Orbital portion is ~3 cm in length
Optic canal extends to the optic chiasm; it then travels through the brain
Visual cortex is found in the occipital lobe of the brain (final destination)
Arterial blood supply (subject to anatomic variation):
Anterior to the lamina cribrosa: Derived from the short ciliary arteries
Posterior to the lamina cribrosa: Derived from the circle of Zinn
Orbital portion: Derived from the pial circulation which are end branches of the ophthalmic and retinal arteries.
Optic nerve venous drainage: The ocular and orbital portions flow primarily into the central retinal vein.
Prevantative Measures
ION in prone spine surgery: Since the etiology is uncertain, preventive measures are speculative.
Colloids as well as crystalloids should be used for resuscitation in large blood loss cases (5) [C].
Head should be positioned level with, or higher than, the heart, if possible (5) [C].
Prone spine surgery: Ensure proper positioning of the head with frequent eye checks to assure that the eyes are pressure free
Cardiac surgery: Efforts should be made to reduce the incidence of emboli during surgery
Diagnosis⬆⬇
Patients should be evaluated in the immediate postoperative period. Vision loss usually manifests as soon as the patient is conscious.
Urgent ophthalmology consult is mandatory.
PION: Optic disk appears normal, initially.
AION: Optic disc edema and hemorrhages on fundoscopic examination.
CRAO: Macular/retinal edema, cherry red spot, or attenuated retinal vessels are typical on fundoscopic examination.
If diagnosis is not apparent after eye examination, then neurological imaging is in order, preferably MRI with gadolinium and stroke protocol technique (6) [C].
Differential Diagnosis
Corneal abrasion
Treatment⬆⬇
ION (anterior and posterior)
Optimize hemoglobin levels, hemodynamic status, and oxygenation (5) [C].
Agents that lower intraocular pressure like acetazolamide have been administered unsuccessfully.
CRAO
Optimize hemoglobin levels, hemodynamic status, and oxygenation (5) [C].
Cortical blindness
Increase oxygen delivery to the visual cortex by optimizing cerebral perfusion pressure and hematocrit (6) [C].
Follow-Up⬆⬇
As per ophthalmology
Closed Claims Data
In 1999, the American Society of Anesthesiologists established the Postoperative Visual Loss Registry to investigate the mechanism of perioperative ION.
As of 2006, 93 spine surgery cases had been collected.
83 cases were diagnosed with ION
10 cases were diagnosed with CRAO
References⬆⬇
LeeLA, RothS, PosnerKL, et al.The American Society of Anesthesiologists Postoperative Visual Loss Registry: Analysis of 93 spine surgery cases with postoperative visual loss. Anesthesiology. 2006;105:652–659
YangS, DrumM, RothS.The prevalence of perioperative visual loss in the United States: A 10-year study from 1996 to 2005 of spinal, orthopedic, cardiac and general surgery. International Anesthesia Research Society. 2009;109:1534–1545.
RothS.Perioperative visual loss: what do we know, what can we do? Br J Anaes. 2009;103:i31–i40.
BergK, HarrisonA, LeeM.Perioperative visual loss in ocular and nonocular surgery. Clin Ophthalmol. 2010;4:531–546.
American Society of Anesthesiologists Task force on Perioperative Blindness. Practice advisory for perioperative visual loss associated with spine surgery. A report by the American Society of Anesthesiologists Task force on Perioperative Blindness. Anesthesiology. 2006;104:1319–1328.
NewmanNJ.Perioperative visual loss after nonocular surgeries. Am J Ophthalmol. 2008;145:604–610.
H47.619 Cortical blindness, unspecified side of brain
Clinical Pearls⬆⬇
Patients undergoing prolonged spinal surgery in the prone position with an expected large blood loss are at increased risk for postoperative blindness.
Consider informing these patients of the risk of visual loss in their preoperative visit.
Consider CVP monitoring.
Balanced colloid and crystalloid resuscitation.
Document positioning and eye checks on anesthesia record.
This injury occurs infrequently so it is difficult to study.