Man referred for acute unilateral vision loss upon waking
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A 55-year-old man at Tufts Medical Center for hypovolemic shock due to a gastrointestinal hemorrhage was referred to the inpatient ophthalmology consult service for left eye acute painless inferior visual field loss upon waking.
The patient felt his vision was at his baseline before going to bed. Upon waking, he noticed a visual field defect in the inferior aspect of his left eye. He denied flashing lights, floaters or eye pain in either eye. He had no visual complaints in his right eye.
Source: Allison Resnik, MD, and Yosbelkys Martin Paez, MD
Two days before evaluation, he had a 3-day history of hematemesis, abdominal pain and lightheadedness in the setting of increased NSAID usage, prompting presentation to Tufts emergency department. On presentation, his systolic and diastolic blood pressures were 120 mm Hg and 55 mm Hg, respectively, and his hemoglobin was 5.6 g/dL. He received three units of packed red blood cells and remained hemodynamically stable over the next 2 days with plans for an esophagogastroduodenoscopy to assess for etiology of blood loss.
Ocular history included type 2 diabetes without retinopathy and pseudophakia after uncomplicated cataract surgery 9 years prior. Medical history included type 2 diabetes, coronary artery disease, hyperlipidemia and erectile dysfunction. Medications included insulin, metformin, naproxen, ibuprofen, quetiapine and tadalafil. Socially, he previously used cocaine (in remission for the past 10 years) and tobacco (10 pack-year history) and currently drinks socially about two glasses of wine a week.
Examination
Visual acuity was 20/20-1 in the right eye and 20/20-1 in the left eye without spectacle correction at distance. IOP was 10 mm Hg in the right eye and 11 mm Hg in the left eye measured via applanation tonometry. Pupils were 2 mm, round and reactive bilaterally without afferent pupillary defect with possible early release of the left pupil. Visual fields to confrontation demonstrated inferior field loss of the left eye. Visual field of the right eye was full. Color vision measured with Ishihara plates was 9 out of 10 in the right eye and 7.5 out of 10 in the left eye. Slit lamp exam of both eyes revealed no conjunctival injection, clear corneas, no signs of anterior chamber inflammation, and posterior capsule IOLs in good position. There was no vitritis. Dilated fundus examination of the right eye revealed a small cup-to-disc ratio of 0.1 with inferior blurring of the optic disc margin without vessel obscuration or peripapillary hemorrhages. Macula, vessels and periphery were unremarkable. Posterior exam of the left eye demonstrated a small cup-to-disc ratio of 0.1 with superotemporal and inferior blurring of the optic disc margin without vessel obscuration or peripapillary hemorrhage. There was a 0.25 disc diameter focal white lesion inferotemporal to the optic disc consistent with a cotton wool spot. There were a few dot-blot hemorrhages in the mid-periphery in both eyes.
What is your diagnosis?
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Acute unilateral vision loss
This patient presented with acute unilateral painless visual field loss in the setting of severe hypotension and acute blood loss from a gastrointestinal hemorrhage. His exam revealed preserved visual acuity of both eyes, without evidence of relative afferent pupillary defect, mild dyschromatopsia in both eyes, and inferior altitudinal painless visual field of the left eye. Dilated exam revealed bilateral crowded nerves with optic nerve head swelling and a cotton wool spot in the left eye.
Management
OCT of the retinal nerve fiber layer (RNFL) was performed and confirmed the findings of the funduscopic exam. The average RNFL thickness was 150 µm in the right eye and 175 µm in the left eye with highest measurement of the superior quadrant of the left eye to 301 µm (Figure 1). There was no subretinal or intraretinal fluid in either eye. OCT through the nerve demonstrated no evidence of superficial or buried optic nerve drusen. OCT ganglion cell analysis revealed an average ganglion cell layer thickness of 104 µm and 101 µm in the right and left eyes, respectively. Humphrey visual field (HVF) 30-2 revealed inferior depression of the left eye (Figure 2) and full field in the right eye. MRI of the brain and orbits with and without gadolinium to rule out any structural cause for the bilateral optic nerve swelling was unremarkable. The patient was educated on the etiology of the disease and informed he may start to notice changes in vision in his right eye. He was instructed to optimize control of his blood pressure and diabetes and to avoid using tadalafil.
Discussion
Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common acute optic neuropathy in patients older than 50 years of age. It is characterized by sudden, painless monocular visual field loss that frequently occurs upon awakening with preserved central visual acuity. Bilateral simultaneous NAION is rare, with studies demonstrating increased risk for bilaterality in men, those younger than 45 years old, those with diabetes, or those who experience episodes of acute hypotension or anemia. It is estimated there is a 15% risk for contralateral involvement within a 5-year period from the initial incident.
The pathogenesis of NAION is not fully understood, but the leading theory is hypoperfusion of the short posterior ciliary arteries supplying the optic nerve induces ischemia and edema to a portion of the optic nerve, leading to eventual apoptosis and death of the ganglion cells. Studies have shown several systemic and ocular risk factors that may increase one’s risk for developing NAION. Ocular risk factors include a crowded “disc-at-risk” and optic nerve drusen in younger patients. Systemic risk factors include hypertension, diabetes, kidney disease, coronary artery disease and obstructive sleep apnea. Certain medications have been hypothesized to increase one’s risk, specifically phosphodiesterase-5 inhibitors, which the patient in our case was prescribed. Preechawat and colleagues analyzed 169 cases of NAION in patients younger than 50 years old and found 11% of cases had simultaneous binocular involvement. Of those cases, anemia was the only statistically significant systemic risk factor compared with patients with unilateral involvement (P < .00003). Our patient experienced a significant anemic and hypotensive event likely explaining the simultaneous bilateral optic nerve involvement.
On ophthalmic examination, the severity of visual impairment can vary widely among individuals with NAION, ranging from 20/20 to 20/400. Clinical exam findings are similar to other optic neuropathies. A relative afferent pupillary defect and decreased color vision are commonly present in the symptomatic eye. The dyschromatopsia is typically proportional to vision loss, unlike what is found in optic neuritis. A case series conducted by Pollock and colleagues demonstrated color vision loss correlates with acuity loss in a linear fashion. However, this series also found a large proportion of cases had retained color vision even with acuity loss. It is hypothesized the ischemic etiology of neural injury leads to sharply delineated foveal injury with sparing of a large portion of extrafoveal macular fibers leading to intact color vision. Confrontation visual fields typically demonstrate an altitudinal defect, more commonly involving the inferior field of vision. If presentation is during the acute phase of NAION, dilated examination reveals a small, crowded hyperemic optic disc with often sectoral optic nerve swelling that corresponds to the area of visual field loss. Peripapillary splinter hemorrhages are commonly seen in up to 75% of patients. It is uncommon for the optic nerve edema to have a pallid appearance. If present, it should warrant further investigation for possible arteritic anterior ischemic optic neuropathy (AAION).
Diagnosis is made clinically based on the patient’s symptoms and examination findings that correlate with typical presentation for NAION. There are several diagnostic imaging tests that can aid in diagnosis, including OCT of the RNFL, which would demonstrate thickening of the RNFL in the acute phase. Unfortunately, studies have shown it may take as long as 3 months for the RNFL swelling to subside and for true optic nerve fiber loss in the area of infarction to be detected. More recently, research has focused on the utility of using the ganglion cell analysis for detecting earlier changes in the disease process. Erlich-Malona and colleagues demonstrated ganglion cell complex thinning in patients with NAION follows an altitudinal, hemispheric pattern that corresponds with visual field loss and can be seen as early as 11 days after injury. Formal HVF testing typically demonstrates superior or inferior altitudinal defects that follow the nerve fiber bundle.
When one presents with concern for NAION, it is of vital importance to rule out possible AAION secondary to giant cell arteritis due to detrimental effects in the fellow eye. If clinical suspicion for giant cell arteritis is high after a thorough review of systems, laboratory tests assessing for inflammatory markers should be pursued. Other etiologies on the differential for unilateral, or bilateral as seen in our case, optic nerve swelling are vast and can often be narrowed down depending on the patient’s history, neuro-ophthalmic examination and ancillary tests. For our case, the differential diagnosis included hypertensive emergency, diabetic papillitis and possible elevated intracranial pressure. If bilateral optic nerve swelling is present, MRI of the brain and orbits can be obtained to rule out intracranial lesion, as was done in this case.
Currently, there is no proven treatment found to be effective for NAION. There have been multiple studies and clinical trials in the literature that have assessed various treatment modalities, both medical and surgical, focusing on decreasing the optic nerve swelling. These include but are not limited to surgical optic nerve sheath decompression, radial optic neurotomy, topical brimonidine, intravitreal and systemic corticosteroids, anti-VEGF agents, antiplatelets and anticoagulants, and plasmapheresis. Thus far, none of these treatments have shown to improve final visual outcomes.
It is important to educate the patient on the timeline of the disease as vision can worsen a few days to weeks after the initial event. Visual acuity typically stabilizes about 2 months from the initial event. In our case, the patient originally experienced vision changes only in the left eye even though optic nerve swelling was seen on examination of the right eye. Subramanian and colleagues discussed cases of this phenomenon in the literature in which patients remain asymptomatic in one eye even with clinical optic nerve swelling found on examination. Eventually, over the course of 2 to 10 weeks, patients develop symptoms in the contralateral eye and subsequent visual field defects.
The pathophysiology and treatment of NAION continue to evolve. Optimizing risk factors to prevent contralateral optic nerve involvement is of utmost importance. Referring the patient for a complete physical examination with their primary care physician is important to optimize blood pressure and diabetes management. Additionally, the patient should undergo a sleep study to assess for undiagnosed obstructive sleep apnea. Avoiding phosphodiesterase-5 inhibitors may also be advised, and administering antihypertensives in the morning may be advocated to avoid nocturnal hypotension.
Clinical course continued
One week after initial presentation, the patient was seen on an urgent basis for acute inferior visual field loss of the right eye. Examination revealed a decline in visual acuity to 20/200 in the right eye and 20/25 in the left eye. A new 2+ relative afferent pupillary defect was seen in the right eye with further dyschromatopsia (1 out of 11 in the right eye, 7.5 out of 11 in the left eye). Posterior exam revealed 360° swelling of the right optic nerve with a peripapillary cotton wool spot. Left optic nerve swelling was mildly improved (Figure 3). OCT of the RNFL was performed, demonstrating worsening of optic nerve swelling, greater in the right eye than the left eye (Figure 4), with new subfoveal subretinal and intraretinal fluid seen bilaterally on OCT of the macula. HVF 30-2 revealed new dense inferior hemifield visual field defect of the right eye and stable inferior altitudinal defect of the left eye (Figure 5).
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- For more information:
- Edited by Yi Ling Dai, MD, and Teresa P. Horan, MD, of New England Eye Center, Tufts University School of Medicine. They can be reached at ydai@tuftsmedicalcenter.org and thoran@tuftsmedicalcenter.org.