RETINA OPHTHALMIC PEARLS Diagnosis and Management of Central Retinal Artery Occlusion entral retinal artery occlusion Approximately 15%-30% of the 1 (CRAO) is an ocular emergency. population has a cilioretinal artery, a CPatients typically present with branch of the short posterior ciliary profound, acute, painless monocular artery. It supplies blood to part or all visual loss—with 80% of affected indi- of the fovea. If a CRAO occurs in such viduals having a final visual acuity of eyes, the cilioretinal artery is spared, counting fingers or worse. CRAO is the typically preserving visual acuity at ocular analogue of a cerebral stroke— 20/50 or better, although peripheral and, as such, the clinical approach and visual field is still severely impaired. management are relatively similar to the management of stroke, in which Risk Factors clinicians treat the acute event, identify The major risk factors for CRAO can be the site of vascular occlusion, and try divided into nonarteritic and arteritic. to prevent further occurrences. The Nonarteritic. More than 90% of incidence of CRAO is approximately 1 CRAOs are nonarteritic in origin. Ipsi- CLASSIC PRESENTATION. Fundus pho- to 2 in 100,000,1,2 with a male predomi- lateral carotid artery atherosclerosis tograph of a patient with right central nance and mean age of 60-65 years. is the most common cause of retinal retinal artery occlusion, evidenced by artery occlusion with a prevalence as widespread ischemic retinal whitening Anatomy high as 70% reported among patients with a classic cherry red spot. The retina receives a dual blood supply, with CRAO or branch retinal artery with the inner retina supplied by the occlusion.3,4 Signs and Symptoms central retinal artery and the outer reti- Other causes of nonarteritic retinal Patients with CRAO usually present na supplied by the choroidal circulation artery occlusion include cardiogenic with sudden and profound unilateral via branches of the posterior ciliary embolism, hematological conditions loss of vision. In a study of 260 eyes with arteries. (sickle cell disease, hypercoagulable CRAO, 74% had presenting visual acu- Both sets of arteries arise from the states, leukemia, lymphoma, etc.), and ity of counting fingers or worse, while ophthalmic artery, the first branch of other vascular diseases, such as carotid the remainder showed some degree of the internal carotid artery just as it exits artery dissection, moyamoya disease, macular sparing that perfused the fovea the cavernous sinus. The ophthalmic and Fabry disease. with resultant better visual acuity.5 artery passes through the optic canal Arteritic. CRAO of arteritic etiology On examination, a relative afferent inferolaterally to the optic nerve. is mostly caused by giant cell arteritis, pupillary defect occurs regardless of On entering the orbit, the central although other vasculitic dis orders such the visual acuity or macular sparing. retinal artery leaves the ophthalmic ar- as Susac syndrome, systemic lupus er- Classic ophthalmoscopic signs include tery and travels within the optic nerve, ythematosus, poly arteritis nodosa, and retinal edema (ischemic retinal whiten- after which it enters the eye, where it granulomatosis with poly angiitis have ing), cherry red spot (due to underlying is subjected to intraocular pressure also been associated with retinal artery normal choroidal circulation [Fig. 1]), changes. occlusion. retinal arteriolar attenuation, and, in the acute phase, segmentation of blood in retinal arterioles (also known as BY SHAUN SIM, MD, AND DANIEL S.W. TING, MD, PHD. EDITED BY SHARON box-carring). A retinal embolus may be 6 Kasi Sandhanam Kasi FEKRAT, MD, AND INGRID U. SCOTT, MD, MPH. visible in up to 40% of patients. The EYENET MAGAZINE • 33 embolic material can be a shiny choles- Table 1: Treatment Options for CRAO terol plaque, gray-white platelet plaque, or white calcium plaque. TREATMENT MECHANISM OF ACTION Associated signs and symptoms may Pharmacological point toward a specific etiology such as IV* acetazolamide Reduce intraocular pressure headache and scalp tenderness in giant cell arteritis, or contralateral sensory or IV mannitol Reduce intraocular pressure motor deficits in carotid artery disease. Topical antiglaucoma medications Reduce intraocular pressure Pentoxifylline Vasodilation to increase blood Evaluation oxygen content In the acute phase of CRAO, optical Inhalation of carbogen Vasodilation to increase blood coherence tomography will show thick- oxygen content ening of the inner retina with sparing of the outer retinal layers. Subsequent Sublingual isosorbide dinitrate Vasodilation to increase blood retinal atrophy and thinning occurs oxygen content after approximately 6 weeks. IV methylprednisolone Reduce retinal edema, only given in Fundus fluorescein angiography in arteritic CRAO the acute phase reveals normal cho- IV or intra-arterial recombinant tis- Thrombolytic therapy to dissolve clot roidal filling with delayed or absent sue plasminogen activator (rt-PA) filling of the central retinal artery. If the Hyperbaric oxygen therapy Increase blood oxygen tension choroidal circulation is also impaired, especially in patients over the age of 50 Surgery/Procedures with CRAO and no visible retinal em- Anterior chamber paracentesis Reduce intraocular pressure boli, giant cell arteritis must be ruled Ocular massage Fluctuation in intraocular pressure to out through laboratory tests such as mechanically dislodge clot erythrocyte sedimentation rate (ESR), Nd:YAG laser embolectomy Lyse or dislodge the clot complete blood count, and C-reactive protein. Pars plana vitrectomy Surgical removal of the clot Systemic evaluation is critical for Lifestyle Modification CRAO patients. They require carotid Optimization of atherosclerotic Secondary prevention artery imaging (carotid duplex ultra- diseases sound, cervical magnetic resonance imaging, or computed tomography an- *IV = Intravenous giography), as the most common cause SOURCE: Developed by the authors. of CRAO is carotid atherosclerosis. A cardiac evaluation in the form of echo- Despite the multitude of treatments neovascularization in 2.5% of cases, cardiography and Holter monitoring purported to be of benefit in acute and the authors found that there was may be required in patients in whom CRAO, there has been no conclusive no causal relationship.10 carotid disease has been ruled out. evidence to support their use. Table The development of neovascular- 1 summarizes the possible treatment ization necessitates prompt panretinal Treatment options. laser photocoagulation to decrease CRAO is a medical emergency. Prompt retinal oxygen demand. referral for stroke evaluation is neces- Complications sary in order to minimize risk of sec- Neovascularization may occur in Conclusion ondary ischemic events such as cerebral patients with CRAO. It may involve CRAO is an ophthalmic and medical or myocardial infarction. the retina, iris, or iridocorneal angle. emergency. The causes of and risk fac- In the acute setting, therapy is There is a debate about the associa- tors for CRAO are similar to those directed at resolving the CRAO and tion of CRAO and the development of of cerebrovascular events. Hence, maximizing visual outcome. Experi- neovascular glaucoma. A prospective patients with CRAO must be evalu- mental studies suggest no detectable study of 33 patients established a tem- ated promptly for stroke to mini mize retinal damage in primate models with poral relationship between CRAO and secondary ischemic events. Despite the CRAO, if retinal blood flow is restored neovascular glaucoma in 15% of cases.8 grim prognosis for CRAO, efforts to re- with in 90 minutes. Subsequent partial These results are corroborated by a store vision—no matter which therapy recovery may be possible if ischemia is retro spective study that showed a mean is used—should be instituted, preferably reversed within 240 minutes.7 However, of 8.5 weeks from diagnosis to clinically within 4 hours of symptoms. occlusions lasting longer than 240 min- evident neovascularization.9 However, utes produce irreversible damage. a prospective study of 232 eyes found 1 Leavitt JA et al. Am J Ophthalmol. 2011;152(5): 34 • AUGUST 2017 820-823. 2 Rumelt S et al. Am J Ophthalmol. 1999;128(6): 733-738. 3 Ahuja RM et al. Stroke. 1999;30(8):1506-1509. 4 Babikian V et al. Cerebrovasc Dis. 2001;12:108- 113. 5 Hayreh SS, Zimmerman MB. Am J Ophthalmol. 2005;140(3):376.e1-e18. 6 Sharma S et al. Arch Ophthalmol. 1998;116(12): 1602. 7 Hayreh SS et al. Ophthalmology. 1980;87(1):75- 78. 8 Duker JS et al. Arch Ophthalmol. 1991;109(3): 339-342. 9 Rudkin AK et al. Eur J Ophthalmol. 2010;20(6): High-quality 1042-1046. 10 Hayreh SS et al. Ophthalmology. 2009;116(10): research from the 1928-1936. world’s leading Dr. Sim is an ophthalmology resident at the Sin- ophthalmic journal gapore National Eye Centre. Dr. Ting is associate consultant at the Singapore National Eye Centre and assistant professor at Duke-National Univer- sity Singapore (Duke-NUS) Medical School. Fi- nancial disclosures: None. The authors would like to acknowledge Mr. Kasi Sandhanam, the ocular imaging specialist from Singapore National Eye Centre, for providing the color fundus photo. 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