Eyeworld

EW FEATURE 36 Neuro-ophthalmology for the anterior segment surgeon • June 2018 AT A GLANCE • A study published earlier this year found that in one dataset nearly 60% of optic neuritis referrals actually had an alternative diagnosis. • Key features of optic neuritis include age between 18 and 55 years old, pain upon eye movement, visual loss, and mild optic nerve swelling in some cases, without hemorrhages. • MRI can help confirm optic neuritis and also stratify patients in terms of possible multiple sclerosis diagnosis or risk. by Liz Hillman EyeWorld Senior Staff Writer overdiagnosis but also the factors that contributing to it. 1 In a ret- rospective, clinic-based, cross-sec- tional study, 122 new patients were referred for acute optic neuritis between January 2014 and October 2016. Of these, 49 (40.2%) had optic neuritis, while 73 (59.8%) had alter- native diagnoses. Why the high rate of initial misdiagnosis? Dr. Van Stavern said major factors were anchoring (or de- ciding upon a diagnosis early in the encounter and not adjusting one's diagnosis with new or competing data based on the examination) and framing (or putting more weight on a clinical feature presented early in the encounter). "Understanding the pitfalls leading to over diagnosis of optic neuritis may improve clinicians' diagnostic process," Stunkel et al. concluded in the study. Diagnosing it right the first time Optic neuritis is inflammation of the optic nerve. A wide variety of autoimmune and infectious diseases can cause optic neuritis, but the vast majority are cases of demyelinating optic neuritis, Dr. Van Stavern said, attributing much of what's known about this condition to the Optic Neuritis Treatment Trial. 2 The latter is often associated with multiple sclerosis and a few other demyelin- ating diseases and can be idiopathic/ post-viral. "For about 20% of multiple sclerosis patients, optic neuritis is their first manifestation of the dis- ease, so it is important to diagnose it accurately to identify patients who are at risk for multiple sclerosis, and to avoid misclassifying patients who are not likely to develop multiple sclerosis," Dr. Van Stavern said. Typically, Dr. Habash said, pa- tients will present with pain on eye movement and changes in vision. With that, she performs a thorough clinical exam, pupil exam, test for color vision and red desaturation (faded red vision), assessment for optic nerve swelling, and a basic neurologic exam. "If there is a high suspicion of optic neuritis," Dr. Habash said, "an MRI is warranted, as it can help determine if the optic nerve is enhancing or if there are white matter lesions. At that point, I usually refer patients to a neuro- ophthalmologist for treatment." Diagnostic pearls to follow and pitfalls to avoid to accurately diagnose this condition M ost comprehensive ophthalmologists have the skills and tools to effectively diagnose optic neuritis, said Gregory Van Stavern, MD, profes- sor, Department of Ophthalmology, and director, Visual Electrophysiolo- gy Services, Washington University School of Medicine, St. Louis. Yet, Dr. Van Stavern and co-in- vestigators reviewed data of acute optic neuritis referrals and found nearly 60% from that set actually had an alternative diagnosis. 1 "We were interested not only in the frequency of overdiagnosis but also what cognitive biases contrib- uted," Dr. Van Stavern said, sharing information from the study and oth- er thoughts on behalf of the whole research team. Ranya Habash, MD, assistant professor of ophthalmology, Bas- com Palmer Eye Institute, Miami, a comprehensive ophthalmolo- gist with a focus on cataract and refractive surgery, regularly staffs residents in the emergency room where optic neuritis cases may first present. Dr. Habash also discussed with EyeWorld what those without a neuro-ophthalmology subspecialty should know about the condition to improve diagnostic accuracy. Overdiagnosis of optic neuritis Stunkel et al. sought to assess not only the incidence of optic neuritis "It can be difficult to diagnose because many times, it's just based on clinical history," Dr. Habash said. "MRI can be a pivotal factor. If the clinical history is suggestive of optic neuritis, I would err on the side of obtaining the MRI because we don't want to miss demyelinating disease." Dr. Van Stavern said the key features to look at are age range (usually 18–55 years old), pain upon movement of the eye, and subjec- tive visual loss, often with scotoma. The clinical features include optic nerve dysfunction in the form of reduced visual acuity, impaired color vision, ipsilateral relative afferent pupillary defect, and optic nerve-related defect, such as central scotoma, arcuate or altitudinal field defect. Dr. Van Stavern noted that the optic disc is actually normal in about two-thirds of patients with optic neuritis and mildly swollen in about one-third. When there is swelling, he said that it's mild and is rarely associated with hemorrhages. "Color vision should be test- ed as this can often differentiate neurogenic from non-neurogenic visual loss," Dr. Van Stavern ex- plained. "Visual field testing should be performed to detect a visual field defect." Dr. Van Stavern said that every patient with demyelinating optic neuritis should have a brain MRI with and without gadolinium. This not only helps confirm optic neuritis but can stratify patients in terms of multiple sclerosis diagnosis or risk. "The newest criteria for mul- tiple sclerosis allow the diagnosis even after a single attack of optic neuritis, depending upon the MRI," Dr. Van Stavern said. "You need to be diligent about checking the pupils before dilation and making sure to check the color plates; these are ancillary tests that can lead you to the right diagnosis, even when an MRI is unavailable," Dr. Habash said. "When we have a high clinical suspicion, we must rule out other major conditions like mul- tiple sclerosis or immune disorders or infections that can cause optic neuritis." Avoiding misdiagnosis "Over diagnosing this condition can be just as harmful as under diagno- sis," Dr. Van Stavern said. "Patients will go online and be terrified that they have multiple sclerosis. MRI scans can be misread, and we have seen patients misdiagnosed as having multiple sclerosis and being subjected to multiple sclerosis treat- ments." According the Stunkel et al. study, the most common alternative Optic neuritis: When it is and when it isn't Severe optic disc swelling with heme, as shown in this picture, is highly atypical for optic neuritis and should raise concerns about an alternate diagnosis. Source: Gregory Van Stavern, MD

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