Ischemic Optic Neuropathy: A Sequala of Spinal Surgery

Noushin S. Ahmed, O.D.

Ocular Disease Resident

Seidenberg Protzko Eye Associates

Havre de Grace, Maryland

Abstract

A 63 year-old female with wet age-related macular degeneration OS>OD presented with a new superior altitudinal defect and decreased vision in her right eye after spinal surgery one week prior.

Clinical examination along with OCT and fundus photos confirmed a non-arteritic anterior ischemic optic neuropathy (NAION).

NAION results from interrupted blood flow to the optic nerve and often leads to long-term vision loss, scotoma, and decreased visual function. Hypotension, hypovolemia, and duration of surgery are all factors during spinal surgery that can induce NAION. Incidence of NAION as a complication is 3 in 10,000 spinal surgeries.

It is crucial for all relevant healthcare providers to be aware of this visually debilitating complication from spinal surgery as this procedure is becoming more prevalent.

Chief Complaint

63YO Female presents complaining of loss of vision in the right eye since lumbar spinal surgery x 6 days ago.

She has also noticed a superior field loss OD as if “a lid has come down.”

No new floaters or flashes of light

No pain, redness, discharge, irritation, or photosensitivity

Ocular History

Dry ARMD OD, Wet ARMD OS x 6 weeks ago

Currently taking Ocuvite; has not received any treatment for the Wet ARMD OS

No changes in the HAG since diagnosis

Wears bifocals

Medical History

Allergies: Acetominophen, Penicillin, Ocycodone, Morphine, Cefoxitin Sodium

Diagnoses: High Blood Pressure

Current Medications: Ocuvite, baby aspirin, HCTZ, Xanax, Hydromorphone, Imdur, Metoprolol succinate

Social History: former smoker; denies drug/alcohol use

Family History

Cataracts: Father

No blindness

Clinical Examination

External

VAcc OD CF @1ft PHNI

OS 20/80 PHNI

Pupils OD PERRL (+) APD

OS PERRL (-) APD

CVF OD Sup field loss OS FTFC

Adnexa normal

Biomicroscopy

Conjunctiva: White & Quiet OU

Cornea: Guttatae 2+ OU

Iris: normal, (-) TID OU

AC: deep & quiet OU

Lens: NS 1+ OU

IOP: 16, 18 mm Hg OD, OS

Fundus Examination

Vitreous: Clear OU

Optic Nerve: OD general disc edema, greatest inferiorly

OS flat, sharp, good color

CD ratio: OD 0.25/0.25; OS 0.35/0.35

Macula: OU RPE migration and multiple hard & soft drusen

Vessels: OD arteriolar narrowing; OS normal

Periphery: OD multiple dot&blot hemorrhages 360,

OS RPE dropout 360

OU flat 360, no holes, tears, detachments

Fundus Photos OD OS

ONH edema (greatest inferiorly)

drusen

drusen

Arteriolarnarrowing

artifact

artifact

ONH Photos OD OS

ONH edema (greatest inferiorly)

ONH photos OD OS

ONH edema (greatest inferiorly)

OCT ONH

ONH edema (greatest inferiorly)

OCT Macula

edema

drusen druse

n

Differential Diagnoses

Central Retinal Artery Occlusion

Retinal Detachment

Perioperative Ischemic Optic Neuropathy

Assessment

1. Perioperative Ischemic Optic Neuropathy, OD

2. ARMD, Dry OU

1. Refer to neuro-ophthalmology for consult and evaluation.

2. Continue Ocuvite supplement and monitor with home amsler grid. OCT showed no signs of wet. Return in 3 months for OCT of macula.

Blood Supply: Optic Nerve1

Blood Supply

Anterior Optic Nerve: Central Retinal Artery Short Posterior Ciliary Arteries Circle of Zinn-Haller

Midorbital Optic Nerve: Small Pial Branches from Internal Carotid Artery

Choroid: Short Posterior Ciliary Arteries

Blood Flow

Blood flow to the optic nerve is controlled by autoregulation 20% of individuals have anomalous autoregulatory

function of circulation to anterior optic nerve Aging, Diabetes, Arterial hypotension interrupt

autoregulation Higher IOP leads to decreased perfusion of retina & optic

nerve

Ischemic Optic Neuropathy (ION)

Compromised blood flow to Optic Nerve

Unilateral Optic nerve dysfunction

Visual Field defect

Afferent Pupillary Defect

Decreased Color vision

Sudden vision loss, without forewarning signs

Painless, irreversible loss of vision

Ischemic Optic Neuropathy

AION1,2,7

Swollen, pale optic nerve

Anterior to the cribiform plate

Arteritic/Non-arteritic NAION most common

with POVL

Decrease of oxygen availability to optic disc

Associated with acute blood loss

PION1,2,7

Intially, disc looks normal (unaffected)->gradual pallor

Ischemia of midorbital optic nerve

Associated with Giant cell arteritis, Lupus, Sickle Cell, Fungal Infection, and surgery

Unrelated to ocular vascular disease

Most frequently reported after spinal surgery 2° to prone positioning

ION and Spinal Surgery

ION most common (89%)1

PION 60% AION 20%

Optic nerve dysfunction occurs within 1-12 days post-op2,5

Visual changes usually occur within first 2 days Loss of color vision Visual Field deficit: central scotomas, peripheral

narrowing, quad/altitudinal defects Relative Afferent Pupillary Defect

Unilateral/bilateral2

Spinal Surgery & Vision Loss

Leading cause of post-operative vision loss (POVL)1

Incidence: 1 in 500 spinal surgeries1

4 Types of Vision Loss1 1. External Ocular Injury: Corneal abrasion, scleral injury

2. Cortical Blindness: 2° to vascular insults to visual tract/cortex

3. Central Retinal Artery Occlusion: direct pressure to globe

4. ION: posterior or anterior depending on location of lesion

Occurred in ages 18-853

No/few comorbidities3

Etiology

Compromised blood flow to Optic Nerve leads to retinal ischemia and vision loss2,3,5-7

Increased IOP and/or decreased Mean Arterial Pressure Decreased perfusion to Optic Nerve Linked to anatomical modification of posterior ciliary artery

circulation7

Edema/Excess Fluid Administration1

Compromise tissue oxygenation from increase in tissue pressure in spaces like the orbital cone1,8

Slows microvascular perfusion = increase in Arterial venous shunting and decrease in sympathetic draining Further increases edema

Removal is by active sodium transport and maintenance of gradient between hydrostatic and colloid osmotic pressure

Small Optic Disc Mechanical obstruction and stasis may reduce axoplasmic flow

Treatment

Hyperbaric Oxygen: increases arterial pressure and hemoglobin8

Blood Transfusions: corrects anemia and hypotension7,8

Acetozolamide: decreases IOP and improves blood flow to optic nerve and retina7,8

Diuretics (Mannitol & Furosemide): decrease edema7,8

Corticosteroids: decrease axonal swelling in acute phase7

However, increases risk for wound infection

Prognosis

No known, established treatment improves visual outcome2,6

Small improvement with retrobulblar steroid injections, antiplatelet blood replacement, therapy, anticoagulants, phenytoin, and norepinephrine

Immediate correction of anemia and hypotension was the only proven valuable treatment7

Irreversible, permanent vision loss7

Vision loss can be temporary, but often severely debilitating3

Very small improvement of visual outcome; very rare complete visual recovery5

Spontaneous recovery may occur, but improvement from No Light Perception is rare6

How did this patient fare?

Unfortunately, this patient was diagnosed too late after surgery, so no treatment was available.

5 days later: HM OD; sup field loss remained—however ONH edema began to resolve

2 weeks later: 20/400 OD; depressed superior field; ONH edema completely resolved

She is now enrolled in low vision services.

Risk Factors

Pre-op2,3,5,7

Anemia

Hypotension

Chronic Hypertension

Diabetes

Artherosclerosis

Smoking

Obesity

Hypercoaguable disease

Anatomical Structural factors of the Optic Nerve

During Operation1-3,6,7

Hypotension <20mm Hg than baseline

Duration of surgery >4-6 hrs6

Blood loss ~ 44.7%7

Replacement Fluids (excessive hydration)

Anemia

Prone Position (greatest risk6)

Combination of the above

Current guidelines

However, the Task Force of Perioperative Blindness4 “does not believe that there are identifiable pre-

operative characteristics that predispose patients to perioperative ION.”4

“believes there is no evidence that an ophthalmic or neuro-ophthalmic evaluation would be useful in identifying at risk patients.”

“believes there is an increased risk for patients in prolonged procedures, blood loss, and/or both.”

High-risk patients should have fluids monitored, head level in a neutral forward position, and vision assessed after waking from anesthesia.

If a visual problem is detected, urgent ophthalmic consultation is recommended for the cause of vision loss

Recommendations1,2,5,7,8

High Risk Patient Recognition

Positioning: avoid prone position and changing head position, protecting the eyes

Hematocrit maintained

Mean Arterial Pressure maintained at baseline

Fluid Control (only treatment modality proven valuable)7

Staging

During Recovery1

Avoid flat positioning Monitor blood pressure Check pupils and Vision Check for orbital edema and tension

After recovery: immediate evaluation of patients with new visual complaints

Future Implications

Sharp increase in the annual number of spinal fusion surgeries performed in the U.S.1,3

From 1996 to 2004: 60,000 to 300,000 A 500% increase The growing aging population leads to an increasing

incidence of chronic vascular disease Dramatic Rise = ominous increase in complications

Recognizing and diagnosing peri-operative vision loss is crucial because other etiologies may be treatable if diagnosed early.6

Summary

Due to low frequency, no prospective study exists identifying origin, prevention, treatment.1

Information has been extrapolated from retrospective reviews and case reports.1

The task force on Perioperative Blindness recommends aggressively maintaining blood pressure & volume at baseline while keeping the head level in a neutral position for high risk patients.

However, there is no patient profile that identifies the high risk patient for ION.7

As the incidence of spinal surgeries increase, complications will continue to rise, indicating the need for awareness of visual complications among patients, eye care professionals, surgeons, and anesthesiologists.

References

1. Baig, Mirza N., Martin Lubow, Phillip Immesoete, Sergio D. Bergese, Elsayed-Awad Hamdy, and Ehud Mendel. "Vision Loss after Spine Surgery: Review of the Literature and Recommendations." Neurosurgical FOCUS 23.5 (2007): E15. Print.

2. Chang, Shu-Hong, and Neil R. Miller. "The Incidence of Vision Loss Due to Perioperative Ischemic Optic Neuropathy Associated With Spine Surgery." Spine 30.11 (2005): 1299-302. Print.

3. Kendrick, Heather. "Post-Operative Vision Loss (POVL) following Surgical Procedures." Journal of Anesthesia & Clinical Research 3.184 (2012): n. pag. Print.

4. Practice Advisory for perioperative visual loss associated with spine surgery: a report by the American Society of Anesthesiologists Task Force on Perioperative Visual Loss. Anesthesiology. 2012 Feb; 116(2):274-85. Print.

5. Myers, Mark A., MD, Steven R. Hamilton, MD, Armen J. Bogosian, MD, Craig H. Smith, MD, and Theodore A. Wagner, MD. "Visual Loss as a Complication of Spine Surgery: A Review of 37 Cases." Spine 22.12 (1997): 1325-329. Print.

6. Ogilvie, James W., MD, and John Sanders, MBBS, FRCA. "Vision Loss following Surgery." AAOS Now (2009): n. pag. Print.

7. Pierce, Vickie, MNA, and Phillip Kendrick, CRNA, PhD. "Ischemic Optic Neuropathy After Spine Surgery." AANA Journal 78.2 (2010): 141-45. Print.

8. Roth, S. "Perioperative Visual Loss: What Do We Know, What Can We Do?" British Journal of Anaesthesia 103.Supplement 1 (2009): I31-40. Print.