Prothrombin G20210A Mutation Causing Nonarteritic Anterior Ischemic Optic Neuropathy in a Young Patient

The recent pandemic has forced us from our usual practice of medicine to alternative means including telehealth visits for the safety of the patients and practitioners. These virtual office visits have left us with few of the tools that we normally rely on. Therefore, there is a greater reliance on clinical skills that can translate in the virtual visit and be helpful for diagnosis.

Letters to the Editor Going Back One Car in the Train: Evaluation of the Relative Afferent Pupillary Defect in the Era of Tele-Neuro-Ophthalmology T he recent pandemic has forced us from our usual practice of medicine to alternative means including telehealth visits for the safety of the patients and practitioners. These virtual office visits have left us with few of the tools that we normally rely on. Therefore, there is a greater reliance on clinical skills that can translate in the virtual visit and be helpful for diagnosis. Here we bring to attention the evaluation of a relative afferent pupillary defect (RAPD), a sign of optic neuropathy, through an old-fashioned method. Galen's second century observation about pupillary reactivity was remarked on by Hirschberg in 1901 (1) that the uncovered eye's dilation was worth observing. Although alternate cover testing was not explicitly described by Gunn, he was doing it in bright light to describe his observation that completely covering the good eye would paradoxically dilate the bad eye. Alfred Kestenbaum measured this difference in pupil size (2), and it was termed Kestenbaum's pupil number (KPN) by Dr. H. Stanley Thompson in his beautifully written treatise in the Second Hoyt Lecture on the history of pupillary function (3). This method is still perfectly suited for today's available technology in the era of tele-neuro-ophthalmology that we outline below: Evaluation of an RAPD in the tele-neuro-ophthalmology video examination as follows: 1. With bright diffuse daylight oriented at the patient's face ask the patient to orient a camera framed closely on both eyes while they fixate at a distant target. 2. Using a large kitchen spoon that can block light ask the patient to alternatively cover each eye. 3. Observe the revealed pupil. If it dilates rather than constricts, this is evidence of an RAPD. 4. Pupils in saved images can be compared and their difference in size documented as KPN, a quantitative measurement is validated against neutral density filters (4). Prothrombin G20210A Mutation Causing Nonarteritic Anterior Ischemic Optic Neuropathy in a Young Patient W e read with interest the article by Francis and Patel (1) and wish to share our experience of managing 7nonarteritic anterior ischemic optic neuropathy (NAION) in young patients. A 47-year-old man presented 442 5. To visualize dark irides, patients' alternately illuminating each eye with a closely held bright light in a dark room is effective and familiar. To quote H.S. Thompson, "When almost every 'discovery' turns out to be a rediscovery, our modern clinical contributions begin to seem like just another car at the end of a long and magnificent train of observations." We have the fortune to walk back one train car length and recall a forgotten but useful clinical skill for our patients today. Linus D. Sun, PhD, MD Departments of Ophthalmology and Neurology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York Jeffrey G. Odel, MD Department of Ophthalmology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York The authors report no conflicts of interest. REFERENCES 1. Hirschberg J. Ueber die Pupillen-Bewegung bei schwerer Sehnerven-Entzündung. Berliner Klinischer Wochenschrift. 1901;38:1173-1175. 2. Fineberg E, Thompson H, Quantitation of the afferent pupillary defect. In: Smith J, ed. Neuro-ophthalmology Focus 1980. New York, NY: Masson Publishing, 1979:25-29. 3. Thompson HS. The vitality of the pupil: a history of the clinical use of the pupil as an indicator of visual potential. J Neuroophthalmol. 2003;23:213-224. 4. Jiang MQ, Thompson HS, Lam BL. Kestenbaum's number as an indicator of pupillomotor input asymmetry. Am J Ophthalmol. 1989;107:528-530. to our hospital with sudden onset painless defective vision in the left eye of 10 days' duration. His best-corrected visual acuity was 20/20 in the right eye (RE) and 20/ 500 in the left eye (LE). Anterior segment was normal in the RE, and a relative afferent defect was present in the LE. Fundus examination of the RE showed a crowded disc, and the LE showed a pallid disc edema (Fig. 1). Visual-evoked potential showed reduced amplitude of P100 in the LE with normal latency. Fundus fluorescein Letters to the Editor: J Neuro-Ophthalmol 2020; 40: 442-443 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Letters to the Editor factors such as diabetes and hypertension, a hypercoagulable work-up is not only useful to protect the other eye from NAION, but given a longer life expectancy in these patients, it could also protect the patient from overall thromboembolic events anywhere else in the body, some of which could be life threatening. FIG. 1. A. Fundus image of the right eye showing crowded disc with absence of physiological cup. B. Fundus image of the left eye showing pallid disc edema. angiography showed LE delayed disc filling followed by late staining. A diagnosis of LE acute NAION was made. He was given a course of systemic steroids, and his vision improved in the LE. Although systemic steroids are controversial in management of NAION (2), we feel it is helpful in young patients (3). Since patient was neither diabetic nor hypertensive and a basic blood work-up including homocysteine levels was normal, a hypercoagulable work-up was performed and he was found to have homozygous mutation in factor II prothrombin gene G20210A. He was referred to a hematologist who recommended lifelong anticoagulation therapy. At 6-month follow-up, he had no recurrences in the LE with a visual acuity of 20/ 125 and his RE continued to be normal and unaffected. Hence, we agree with Dr. Francis that in a setting of a young patient ,50 years of age with no systemic risk Should a Hypercoagulable Workup Be Performed on Young Patients with Nonarteritic Anterior Ischemic Optic Neuropathy?: Response W e would like to thank M. K. Kumar and his colleagues for sharing their experience regarding their patient's clinical presentation, Prothrombin G20210A mutation, and its proposed causative link to his development of non-arteritic anterior ischemic optic neuropathy (NAION) at the relatively young age of 47. Indeed, there are other such case reports in the literature describing NAION occurring in patients with such mutations, without a previous history of thrombotic or ischemic events occurring elsewhere in the body. If there is a causal association, it is unclear to me why NAION would preferentially occur, without a history of much more common presentations of thrombosis. It is certainly compelling to prospectively anticoagulate a patient with NAION who is subsequently found to harbor this mutation; however, causa- Letters to the Editor: J Neuro-Ophthalmol 2020; 40: 442-443 Mani Karthik Kumar, MS Mansha Daswani, DNB Virna M. Shah, DO Department of Neuro-Ophthalmology, Aravind Eye Hospital & Postgraduate Institute of Ophthalmology, Coimbatore, India [e-mail] The authors report no conflicts of interest. REFERENCES 1. Francis CE, Patel VR. Should a hypercoagulable work-up be performed on young patients with nonarteritic anterior ischemic optic neuropathy? J Neuroophthalmol. 2019;39:523-528. 2. Saxena R, Singh D, Sharma M, James M, Sharma P, Menon V. Steroids versus no steroids in nonarteritic anterior ischemic optic neuropathy: a randomized controlled trial. Ophthalmology. 2018;125:1623-1627. 3. Hayreh SS, Zimmerman MB. Non-arteritic anterior ischemic optic neuropathy: role of systemic corticosteroid therapy. Graefes Arch Clin Exp Ophthalmol. 2008;246:1029-1046. tion is still not confirmed. We do know that venous thrombotic disease is much more common with the G20210A mutation than arterial thrombosis. Accordingly, if we were to assign causation in such cases, are we making the pathophysiological argument that venous thrombosis at the level of the laminar and prelaminar circulation subsequently leads to local arterial insufficiency and subsequent infarction? If we can agree on this potential mechanism, then the plausibility of causation and recommendations to routinely screen for all hypercoagulable states (venous and arterial) can be made for our NAION patients, regardless of age at presentation. Vivek R. Patel, MD University of Southern California, Roski Eye Institute, Keck School of Medicine, Los Angeles, California The author reports no conflicts of interest. 443 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.