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Man experiences acute loss of vision in postoperative period
Dilated fundus exam of the left eye revealed 360° of blurred disc margin with two peripapillary flame hemorrhages.
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A 69-year-old man was transferred to Tufts Medical Center for acute loss of vision in his left eye. Nine days prior to presentation, he underwent coronary artery bypass grafting. The next day after discharge from the hospital, he noticed a “gray wall” in his inferior vision that progressed superiorly to involve his entire field of view. He went to a local emergency room where an MRI of the head was unremarkable. He was transferred to Tufts Medical Center for ophthalmologic evaluation and was admitted to the medicine service.
The patient’s blood pressure at the time of admission was 95/53. He denied pain, headache, jaw claudication, scalp tenderness, fevers or weight loss. His medical history was remarkable for hypertension, hyperlipidemia, abdominal aortic aneurysm and postoperative paroxysmal atrial fibrillation, for which he was started on amiodarone. His ocular history was significant only for myopia.
Examination
On examination, the patient’s uncorrected vision at near was 20/25 in the right eye and no light perception in the left eye. His pupils measured 4 mm bilaterally, with his right pupil constricting to 2 mm with light, while his left pupil constricted sluggishly to 3 mm and demonstrated a relative afferent pupillary defect. His anterior exam was remarkable only for moderate nuclear sclerosis in both eyes. Dilated fundus exam revealed 360° of blurred disc margin in the left eye with two peripapillary flame hemorrhages, while his right eye revealed a cup-to-disc ratio of 0.1 (Figure 1). At the time of his exam, the patient’s blood pressure was 71/44.
Figure 1. Color fundus photos revealing optic nerve head edema and peripapillary flame hemorrhages in the left eye.
Images: Muakkassa N, Hedges TR
What is your diagnosis?
Unilateral loss of vision
The differential diagnosis of an elderly man with painless, acute, unilateral loss of vision with optic disc edema includes arteritic or nonarteritic anterior ischemic optic neuropathy, central retinal vein occlusion, optic neuritis, diabetic papillopathy, toxic optic neuropathy, optic nerve compression by a tumor or neoplastic infiltration of the optic nerve. Given the patient’s presentation, there was significant concern about arteritic anterior ischemic optic neuropathy. However, nonarteritic anterior ischemic optic neuropathy, postoperative ischemic optic neuropathy and amiodarone-associated optic neuropathy were also considered.
Anterior ischemic optic neuropathy (AION) results from ischemia of the optic nerve head. Nonarteritic ischemic optic neuropathy (NAION) comprises 90% to 95% of cases. Risk factors for NAION include small physiologic cup in the contralateral eye (“disc at risk”), hypertension, diabetes, smoking, obstructive sleep apnea and hyperlipidemia. In arteritic anterior ischemic optic neuropathy (AAION), there is concern for rapidly progressive visual loss of the involved eye as well as involvement of the fellow eye. Therefore, prompt administration of steroids is essential in suspected cases.
The diagnosis of AAION rather than NAION is suggested by several presenting features. The arteritic form can present with systemic symptoms including headache, scalp tenderness and jaw claudication, as well as elevated inflammatory markers. Fluorescein angiography often reveals delayed choroidal filling, and diagnosis is confirmed by temporal artery biopsy.
Amiodarone has been described to cause an optic neuropathy that resembles AION. It is thought to occur secondary to accumulation of lamellated inclusion bodies in optic nerve axons. Amiodarone-associated optic neuropathy is a clinical diagnosis. It is typically bilateral with mild optic nerve dysfunction and insidious in onset with mean time to onset of 6 months. Postoperative or perioperative optic neuropathy is usually seen immediately or within days of cardiac or spinal surgery and usually affects the posterior optic nerves.
Diagnosis and management
Erythrocyte sedimentation rate and C-reactive protein were 61 mm/hr and 59 mg/dL, respectively, and the patient was started on intravenous methylprednisolone. Amiodarone was discontinued; however, amiodarone-associated optic neuropathy was considered highly unlikely given the acute onset, unilateral involvement and presentation only 7 days after initiation of therapy. Optical coherence tomography imaging revealed increased thickness of the retinal nerve fiber layer (Figure 2) and disc edema (Figure 3). Fluorescein angiography performed on hospital day 3 showed a patchy area of delayed choroidal filling, delayed disc filling and late disc leakage (Figure 4), raising further concern for AAION. However, a subsequent temporal artery biopsy was negative for arteritis, and the patient was tapered off steroids and diagnosed with NAION. Postoperative ischemic optic neuropathy was considered unlikely given that it was anterior and that the patient did not develop symptoms until 7 days after surgery. Given his course of postoperative hypotension, his diagnosis was presumed to be hypotension-induced NAION. His vision did not improve, and his fellow eye is unaffected to date.
Figure 3. High-definition OCT revealing optic nerve head elevation of the left eye.
Figure 4. Fluorescein angiography reveals choroidal hypoperfusion and delayed disc filling at 18 seconds and 22 seconds (a and b) with resolution of choroidal hypoperfusion by 35 seconds (c) and disc leakage at 5 minutes 21 seconds (d).
Discussion
The role of hypotension in AION is not fully characterized. Hypotension is thought to result in hypoperfusion and subsequent ischemia of an optic nerve head already predisposed to ischemia. An association between nocturnal hypotension and progression of visual field defects has been described in patients with NAION on oral antihypertensive therapy. Seventy-three percent of cases of NAION have been reported to occur soon after wakening from sleep, further establishing the role of hypotension in the precipitation of NAION. There is some evidence showing improvement in vision after prompt reversal of hypotension.
Posterior ischemic optic neuropathy (PION), which often occurs in the postoperative period, may occur by a similar mechanism, resulting in ischemia of the intraorbital optic nerve rather than the optic nerve head. These patients present with acute loss of vision and signs of optic neuropathy but without optic nerve head edema. Contributing factors include prone positioning (resulting in elevated venous pressure, elevated IOP and poor disc perfusion), prolonged operations, blood loss, diabetes, anemia and hypotension. Most of these patients do not recover vision. However, there is a single report in the literature describing improvement in visual acuity of bilateral PION after prompt reversal of postoperative anemia and hypotension.