Nonarteritic Anterior Ischemic Optic Neuropathy: Exceptions to the Rules

Clinical Correspondence Section Editors: Robert Avery, DO Karl C. Golnik, MD Caroline Froment, MD, PhD An-Gour Wang, MD Nonarteritic Anterior Ischemic Optic Neuropathy: Exceptions to the Rules Michael S. Vaphiades, DO, Zakeya M. Al-Sadah, MD, Lanning B. Kline, MD A 61-year-old woman was noted to have asymptomatic right optic disc edema (ODE) on routine eye examination. She was ultimately referred for neuro-ophthalmic evaluation 9 months later. She denied jaw claudication, scalp tenderness, weight loss, fever, chills, or headache. Visual acuity was 20/30 in the right eye and 20/20 in the left FIG. 1. There is right optic disc edema of 9 months’ duration. FIG. 2. Mild central depression is present in the right visual field while the left field is normal. Department of Ophthalmology, Callahan Eye Hospital, Birmingham, Alabama. Supported in part by an unrestricted grant from the Research to Prevent Blindness, Inc, New York, NY. The authors report no conflicts of interest. Address correspondence to Michael S. Vaphiades, DO, Department of Ophthalmology, UAB, Suite 601, 700 South 18th Street, Birmingham, AL 35233; E-mail: [e-mail]. Vaphiades et al: J Neuro-Ophthalmol 2021; 41: e139-e141 eye. Color vision was normal bilaterally, and pupillary reactions were intact without a relative afferent pupillary defect. The anterior segments were normal in appearance while funduscopy revealed right ODE; the left optic nerve was normal without edema (Fig. 1). Automated visual fields (Humphrey 30-2) showed slight central depression of the right eye (Fig. 2). e139 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Correspondence FIG. 3. There is right optic disc edema with superior visual field loss. FIG. 4. The right optic disc edema has resolved with some improvement in the right visual field defect. The patient had a history of obstructive sleep apnea, hypertension, diet-controlled diabetes mellitus, hyperlipidemia, hypothyroidism, and gastroesophageal reflux. Medications included aspirin, atenolol, atorvastatin, levothyroxine, and omeprazole. Laboratory results included erythrocyte sedimentation rate of 12 mm/hour and negative testing for Bartonella henselae, Lyme, syphilis, tuberculosis, Rocky Mountain spotted fever, and Toxoplasma gondii. Complete blood count and basic metabolic profile were normal. Contrasted brain and orbital fat-suppressed MRI studies were unremarkable without evidence of optic nerve enhancement. A lumbar puncture showed an opening pressure of 16 cm H2O with a normal CSF formula except for a slightly e140 Vaphiades et al: J Neuro-Ophthalmol 2021; 41: e139-e141 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Correspondence elevated protein of 68 mg/L (12–60) which we ascribed to her diabetes. Six months later, the patient reported a 5-day history of a “dark gray band” in her right visual field. At that time, acuity in her right eye was 20/25 with a superior field defect and persistent right ODE (Fig. 3). She was examined 1 and 3 months later (16 months after the onset of right ODE) with some improvement of the right disc edema. At the time of the examination 3 months later, the right optic disc swelling was no longer present. Thus, 19 months after the onset of right ODE, visual acuity in the patient’s right eye was 20/20, the right visual field defect had improved, and the disc edema had resolved (Fig. 4). The patient has remained stable over the ensuing 9 months. The temporal profile of our patient’s clinical course highlights 2 aspects of nonarteritic anterior ischemic optic neuropathy (NAION): 1) incipient NAION and 2) prolonged resolution of ODE. In 1981, Hayreh (1) reported 4 patients in whom unilateral ODE was detected, yet visual function, including acuity and visual fields, was normal. However, over the next 2–4 months, these patients experienced a decline in visual acuity and development of a visual field defect. Hayreh identified 7 previously reported cases with asymptomatic ODE, progressing to sudden visual loss over a period of 3 days to 6 months. Subsequently, he termed this entity “incipient NAION” (2) and described 54 such patients (60 eyes) that he evaluated over a period of 27 years. In those individuals who progressed to classic NAION, the timing ranged from 3.2 to 10.1 weeks and the longest time to resolution of ODE was 17.7 weeks (3). Our patient’s course was unusual in that it took 15 months (65 weeks) for her to note a change in vision with associated visual field loss. Of additional concern was the fact that for our patient’s right ODE was present for 19 months (82.5 weeks). This, too, is highly unusual for NAION as ODE typically resolves within 5–18 weeks (3,4). As Hayreh and Zimmerman (3) cautioned: “Because the main feature of incipient NAION is asymptomatic optic disc edema (ODE), how to differentiate such ODE from ODE resulting from other causes is a particular challenge and with complete ocular, orbital, neurologic, and systemic evalua- Vaphiades et al: J Neuro-Ophthalmol 2021; 41: e139-e141 tions, one can usually differentiate these possibilities from incipient AION.” Others have voiced similar concerns (5). Thus, we proceeded with a systemic evaluation for our patient’s ODE, including a series of hematologic studies and brain MRI. It should be noted that since incipient NAION is detected on routine examination, it is impossible to know the exact duration of ODE. The pathogenesis of our patient’s clinical course is uncertain. It may be that although axoplasmic stasis from ischemia leads to ODE, ischemia may not necessarily lead to impaired axonal conduction or cause visual impairment from axonal infarction (3). Possibly, it is the degree of ischemia of the optic nerve head that not only dictates changes in structure (edema) but also in function (visual loss). Our report serves as a reminder that, at times, NAION may follow a protracted time course, and this may prompt concern for other causes of optic nerve edema. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: L. B. Kline and Z. M. Al-Sadah; b. Acquisition of data: L. B. Kline and Z. M. Al-Sadah; c. Analysis and interpretation of data: L. B. Kline and Z. M. Al-Sadah. Category 2: a. Drafting the manuscript: L. B. Kline; b. Revising it for intellectual content: L. B. Kline. Category 3: a. Final approval of the completed manuscript: L. B. Kline. REFERENCES 1. Hayreh SS. Anterior ischemic optic neuropathy. V. Optic disc edema an early sign. Arch Opthalmol. 1981;99:1030–1040. 2. Hayreh SS. Acute ischemic disorders of the optic nerve: pathogenesis, clinical manifestations and management. Ophthalmol Clin North Am. 1996;3:407–442. 3. Hayreh SS, Zimmerman MB. Incipient nonarteritic anterior ischemic optic neuropathy. Ophthalmology. 2007;114:1763–1772. 4. Chua D, Cullen JF. Incipient non-arteritic anterior ischemic optic neuropathy: a distinct clinical entity, the Singapore Scene 3. Singapore Med. 2014;55:473–475. 5. Arnold AC. Ischemic optic neuropathy. In: Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology. 6th edition. Philadelphia, PA: Lippincott Williams & Wilkins, 2005:366. e141 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.