Posterior Ischemic Optic Neuropathy (PION)

Key Points at a Glance

Key Points of This Disease

• Posterior ischemic optic neuropathy (PION) is an acute optic neuropathy due to ischemia of the optic nerve posterior to the lamina cribrosa, and does not involve optic disc swelling in the acute phase.
• It is classified into three types: non-arteritic, arteritic (giant cell arteritis [GCA]), and perioperative.
• PION accounts for only about 10% of all optic nerve ischemia cases, making it a rare disease.
• In the acute phase, the optic disc appears normal, and disc pallor appears 6 to 8 weeks later, so it is a diagnosis of exclusion.
• Arteritic PION requires immediate administration of high-dose steroids.
• Perioperative PION is often bilateral, severe, and irreversible, with no established treatment.
• The incidence after spinal surgery is reported as 0.087%, and after neck dissection as 0.08%. ¹⁾

1. What is Posterior Ischemic Optic Neuropathy (PION)?

Posterior Ischemic Optic Neuropathy (PION) is an ischemic optic neuropathy caused by circulatory insufficiency in the optic nerve posterior to the lamina cribrosa. It is clearly distinguished from anterior ischemic optic neuropathy (AION) by the absence of optic disc swelling in the acute phase. Anterior ischemic optic neuropathy (AION) presents with disc swelling in the acute phase and is classified into arteritic (AAION) and non-arteritic (NAION) types based on etiology. NAION is essentially always anterior, while arteritic PION is classified as posterior (PAION).

PION is a rare disease accounting for only about 10% of all optic nerve ischemia cases, and it occurs more frequently after age 50. It is classified into the following three types:

• Non-arteritic PION: Secondary to small vessel disease. This is the rarest type.
• Arteritic PION (giant cell arteritis-related): Caused by inflammation and occlusion of the posterior short ciliary arteries (PCA) due to giant cell arteritis.
• Perioperative PION: Occurs after non-ophthalmic surgery. Frequently reported after spinal surgery and neck dissection.

Q How is PION different from AION?

A

The main difference is the optic disc appearance in the acute phase. In AION, disc swelling occurs acutely, whereas in PION, the disc appears normal in the acute phase, and pallor (atrophy) appears 6 to 8 weeks later. The site of ischemia is anterior to the lamina cribrosa in AION and posterior to the lamina cribrosa in PION.

2. Main Symptoms and Clinical Findings

posterior ischemic optic neuropathy dwi mri

Using diffuse weighted image and apparent diffusion coefficient in MRI for diagnosis of posterior ischemic optic neuropathy in a young male: a case report and literature review. BMC Ophthalmol. 2022 Apr 14; 22:168. Figure 4. PMCID: PMC9009014. License: CC BY.

T2WI DWI showed focal high intensity signal at the left optic nerve. (Red arrow)

Subjective Symptoms

• Acute and painless vision loss: Occurs in one or both eyes. Usually develops within hours, but may worsen over days to weeks.
• Characteristics of perioperative PION: Vision loss is first noticed upon awakening from anesthesia. It may also become apparent a few days after surgery.
• Severity differences by type: Perioperative PION causes bilateral, severe, and permanent vision impairment in 70% of cases.

Q How much does vision decrease?

A

It varies greatly by type. In non-arteritic PION, 69% of cases have visual acuity of 20/200 or worse, and only 20% maintain 20/40 or better. In perioperative PION, the most common final visual acuity is no light perception (NLP), and 75.8% of eyes have counting fingers or worse. ¹⁾

Clinical Findings (Findings Confirmed by Physician Examination)

• Positive RAPD: Relative afferent pupillary defect (RAPD) is observed in unilateral or asymmetric cases.
• Acute fundus findings: Both ophthalmoscopy and fluorescein angiography (FA) are normal. The optic disc appears normal.
• Visual acuity range: Ranges from normal to no light perception (NLP).
• Visual field defects: Central visual field defects are most common. Altitudinal defects are also observed.
• After 6–8 weeks: Optic disc pallor appears, mainly on the temporal side.
• Ischemic optic atrophy: Can occur in both arteritic and non-arteritic forms. The difference from glaucoma is the presence of pale atrophy of the optic rim.

Non-arteritic

Optic disc findings: Normal in the acute phase. Pallor develops after 6–8 weeks.

Visual acuity: 20/200 or worse in 69%.

Course: Rare onset. Steroid therapy has been reported to improve visual fields.

Arteritic (giant cell arteritis)

Optic disc findings: Normal in the acute phase. Pallor develops later.

Systemic symptoms: Accompanied by headache, jaw claudication, and elevated ESR/CRP.

Course: Visual recovery is less likely than in non-arteritic PION.

Perioperative

Onset pattern: Noticed upon awakening or within a few days after surgery.

Affected side: Bilateral in 70%.

Course: Most severe. NLP is the most common outcome.

3. Causes and Risk Factors

Non-arteritic PION

Secondary to microvascular disease, involving the following vascular risk factors.

• Diabetes mellitus (P=0.014), hypertension (P=0.022), migraine (P=0.039)
• Arteriosclerosis, glaucoma, carotid artery dissection, carotid-cavernous fistula
• Hemodialysis, head trauma
• Hypertension and arteriosclerosis impair the autoregulatory mechanism of the optic nerve.

Arteritic PION (giant cell arteritis-related)

• Inflammation and occlusion of the posterior ciliary arteries (PCAs) due to giant cell arteritis are the main cause.
• Other orbital arteries may also be involved.
• More common in the elderly, with a lower chance of visual recovery than non-arteritic non-surgical PION.

Perioperative PION

Occurs in younger patients than arteritic PION. The following risk factors are known.

Pre-existing risk factors:

• Male sex, obesity, obstructive sleep apnea syndrome
• Use of amiodarone or PDE-5 inhibitors

Intraoperative risk factors:

• Prolonged arterial hypotension, postoperative anemia
• Decreased ocular perfusion pressure (MOPP) due to elevated intraocular pressure (IOP) (MOPP = mean arterial pressure (MAP) − IOP)
• Facial edema, prone position

Associated surgical procedures (in order of frequency):

• Spinal surgery (54.2% of reported cases): Use of Wilson frame, intentional hypotension, prone position under general anesthesia are risk factors¹⁾
• Radical neck dissection (13.3%): Venous congestion due to compression/ligation of the internal jugular vein (IJV) is involved in the mechanism¹⁾
• Others: Cardiac bypass, blepharoplasty, sinus surgery, hip surgery, radical prostatectomy, etc.

The incidence after spinal surgery is reported as 0.087%, and after neck dissection as 0.08%.¹⁾

Prevention and daily care

Please appropriately control vascular risk factors (hypertension, diabetes, arteriosclerosis). If you are planning major surgery such as spinal surgery, be sure to inform your ophthalmologist and attending physician beforehand about any history of obesity, hypertension, diabetes, etc. If you notice any changes in vision after surgery, promptly consult an ophthalmologist.

Q What is the risk of developing PION after surgery?

A

The incidence after spinal surgery is reported as 0.087%, and after neck dissection as 0.08%.¹⁾ Although the frequency is low, the visual prognosis is extremely poor once it occurs, so preoperative explanation and perioperative management for high-risk patients are important.

4. Diagnosis and examination methods

PION is a clinical diagnosis and also a diagnosis of exclusion. The diagnostic process is as follows.

The process involves: acute vision loss + visual field defect + positive RAPD + normal optic disc findings in the acute phase → optic disc pallor after 6–8 weeks → exclusion of other causes (retrobulbar optic neuritis, retinal disease, compression, toxicity, etc.). Perioperative PION is relatively straightforward to diagnose because vision loss occurs after non-ophthalmic surgery.

Blood Tests (Differentiating Arteritic vs. Non-Arteritic)

In patients aged 50 years or older, measure ESR and CRP to rule out giant cell arteritis.

The sensitivity and specificity of each test for diagnosing giant cell arteritis are shown below.

Test	Sensitivity	Specificity
ESR + CRP combined	Up to 100%	97%
Thrombocytosis	57.0%	96.5%
Low hemoglobin	46.3%	92.9%
Decreased hematocrit	39.8%	91.3%
Leukocytosis	28.1%	85.7%

CRP has higher specificity than ESR. The reference value for ESR is half of age for men and half of (age + 10) for women. Temporal artery biopsy (TAB) is the gold standard for diagnosing giant cell arteritis, with sensitivity and specificity both over 95% when performed properly. Biopsy should be performed within a few days even after starting steroid treatment. In non-arteritic PION, these test values are normal.

Imaging (MRI)

• Diffusion-weighted imaging (DWI): Restricted diffusion (decreased ADC) may be observed in the posterior optic nerve. This occurs due to cytotoxic edema causing water accumulation within cells. However, successful cases are rare.

Visual Evoked Potentials (VEP)

• Useful for differentiating from retrobulbar optic neuritis (non-specific).
• In PION, decreased amplitude is predominant. In retrobulbar optic neuritis, prolonged latency is predominant.
• VEP latency prolongation of 30 ms or more suggests retrobulbar optic neuritis rather than PION.
• Electroretinogram and fluorescein angiography show normal findings at onset.

Differential Diagnosis

The main differential diagnoses include retrobulbar optic neuritis, macular/retinal diseases, toxic optic neuropathy, and compression or inflammation of the posterior optic nerve. To differentiate ischemic optic neuropathy from retrobulbar optic neuritis, VEP, electroretinography, OCT, and DWI MRI are used in combination.

5. Standard Treatment

Arteritic PION (Giant Cell Arteritis-Related)

The following protocol is recommended:

• Acute phase: Intravenous methylprednisolone (steroid) 1 g/day for 3–5 days.
• Maintenance phase: Switch to oral prednisolone 1 mg/kg/day.
• Tapering: Taper slowly over at least 4–6 months while monitoring ESR levels. In some cases, more than 1 year may be required.
• Note: Alternate-day steroid dosing is not recommended.

According to overseas reports, the median initial dose is prednisolone 80 mg/day, which is tapered after ESR and CRP stabilize. The total treatment duration including tapering is approximately 2.5 months.

Non-Arteritic PION

No established effective treatment exists. Anticoagulation therapy, vasodilators, oral steroids, and optic nerve sheath decompression have been attempted, but no significant improvement in visual prognosis has been demonstrated. A regimen of prednisolone 80 mg/day for 2 weeks followed by tapering may be considered, but no RCT data are available.

Perioperative PION

No established treatment exists. Steroids are generally not recommended. General measures include:

• Management of vascular risk factors (minimize bleeding, maintain appropriate MAP)
• Minimization of prone positioning
• Maximization of venous return from the head

Practice Advisory for Spinal Surgery (Perioperative Management Guidelines)

Systematic preoperative, intraoperative, and postoperative management is important for preventing vision loss.

Preoperative:

• Assessment of anemia, obesity, and vascular risk factors (hypertension, diabetes, history of stroke, smoking)
• Explain the risk of vision loss to high-risk patients

Intraoperative:

• Continuous monitoring of systemic blood pressure in high-risk patients
• Use induced hypotension only when absolutely necessary (implement after multidisciplinary collaboration)
• Treat prolonged hypotension appropriately
• Maintain arterial pressure at a higher level in hypertensive patients
• Frequent monitoring of Hb/Ht in high-risk patients with significant bleeding
• Maintain circulating blood volume with blood transfusions, crystalloids, and colloids
• Position management: Keep the head neutral, facing forward, and at the same level as or higher than the body. Avoid direct pressure on the eyes, and check eye position periodically during surgery.

Postoperative:

• Check vision upon awakening. If concerned, obtain immediate ophthalmology consultation.
• Maintain appropriate SpO₂, hemodynamics, and Hb/Ht.

Treatment considerations

• If arteritic PION is suspected, start steroid treatment immediately without waiting for test results.
• Alternate-day steroid dosing is not recommended.
• Visual improvement in the affected eye is limited; the main goal of treatment is to prevent progression and involvement of the fellow eye.

Q Can vision in PION recover?

A

Prognosis varies greatly by subtype. In arteritic PION, immediate steroid administration can reduce progression and fellow eye involvement, but significant improvement in already reduced vision is unlikely. Perioperative PION does not respond to steroids and often follows a bilateral, irreversible, and severe course. For non-arteritic PION, some reports show visual field improvement with steroids, but there is no established evidence.

6. Pathophysiology and detailed pathogenesis

Blood supply and anatomy of the optic nerve

The posterior optic nerve is divided into three segments: intraorbital, intracanalicular, and intracranial. The retrolaminar optic nerve receives blood supply from the pial vascular plexus and branches of the central retinal artery.

• Intraorbital segment: Dual supply from the pial vascular network (peripheral centripetal) and central retinal artery branches (axial centrifugal).
• Intracanalicular portion: Only a peripheral centripetal system from branches of the ophthalmic artery.
• Intracranial portion: Only the pial vascular network.

Mechanism of ischemia

• Ischemia occurs in the pial vascular network and spreads to the optic nerve.
• In ischemia of the centrifugal vascular system, the central part of the nerve tends to be preserved.
• In ischemia of the centripetal vascular system, the peripheral part of the nerve tends to be preserved (more common in both arteritic and non-arteritic PION).

Mechanism of perioperative PION

Postoperative hemorrhage and increased intracranial pressure due to bilateral internal jugular vein (IJV) compression reduce optic nerve perfusion, contributing to the development. ¹⁾ IJV ligation has been suggested as a risk factor for ischemic optic neuropathy, and impaired arterial perfusion due to venous congestion is assumed. ¹⁾ The mechanisms of reduced oxygen supply include: ① low oxygen levels in circulating blood, ② decreased arterial perfusion pressure, and ③ increased blood flow resistance. ¹⁾

Histopathology

• Ischemia may spare the peripheral or central segment, or may lead to total infarction.
• Microscopic findings: acellularity of fibrovascular pial septa, mild hemorrhage, gitter cell infiltration, and myelin loss.

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7. Latest research and future perspectives (research-stage reports)

For patients: Please read

The following content is currently at the research stage or under clinical trial, and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Case reports of PION due to postoperative hemorrhage and IJV compression

Kohyama et al. (2022) reported a case of PION that developed after laryngopharyngectomy with bilateral neck dissection and free jejunal flap reconstruction. ¹⁾ This is considered the first reported case of PION caused by postoperative hemorrhage and bilateral IJV compression.

Surgery time 13.5 hours, total blood loss 740 g. Systolic blood pressure dropped from approximately 150 mmHg preoperatively to a minimum of 80 mmHg (for several minutes). Hemoglobin decreased from 13.5 g/dL preoperatively to 9.5 g/dL postoperatively, then dropped sharply to 6.1 g/dL due to hemorrhage. Hematocrit decreased from 38.1% preoperatively to 29.3% postoperatively, then dropped to 19.3%. Postoperatively, facial and neck edema occurred, and both IJVs were compressed by hematoma. ¹⁾

Oral prednisolone at 1 mg/kg/day was administered for more than 2 months, but visual acuity remained at the level of light perception without improvement, and no visual recovery was observed even after 1 year. ¹⁾ There was a 7-hour delay from the onset of edema to the release of the hematoma, and the authors suggest that early exploratory incision might have prevented PION. ¹⁾ It has also been reported that 75.8% of eyes with perioperative PION have visual acuity of counting fingers or worse. ¹⁾

Steroid therapy for non-arteritic PION

Regarding steroid therapy for non-arteritic PION, significant improvement in visual field (P=0.030) was observed in the steroid-treated group compared to the control group, and significant improvements in visual field (P<0.001) and visual acuity (P=0.031) were also reported relative to baseline. However, no RCT data are available.

Attempts at hyperbaric oxygen therapy

There are reports that the combination of hyperbaric oxygen therapy within 72 hours of onset and steroids was successful in a small number of cases of perioperative PION. Further case accumulation and research are awaited.

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8. References

1. Kohyama K, Kato H, Kuroki M, et al. Posterior ischemic optic neuropathy following postoperative bleeding and internal jugular vein compression. Nagoya J Med Sci. 2022;84(4):877-883.
2. Wang MY, Brewer R, Sadun AA. Posterior ischemic optic neuropathy: Perioperative risk factors. Taiwan J Ophthalmol. 2020;10(3):167-173. PMID: 33110746.
3. Patel AU, Patel US, May EF. Posterior Ischemic Optic Neuropathy Because of Hematologic Malignancy. J Neuroophthalmol. 2024;44(1):e52-e54. PMID: 36729041.