ischemic optic neuropathy: a sequala of spinal surgery
DESCRIPTION
ION, spinal surgeryTRANSCRIPT
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.