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The Official Scientific Journal of Delhi Ophthalmological Society
Central Retinal Arterial Occlusion Following Schwannoma Resection
Navneet Mehrotra, Manish Nagpal, Hardik Jain, Avijit Vishnoi, Rakesh Juneja, Ashish Jain
Retina Foundation & Eye Research Centre, Ahmedabad, Gujrat, India
Corresponding Author:
Hardik Jain
DOMS, FRF
Retina Foundation
Shahibaug under bridge
Ahmedabad, India
Email id: hardy2512@gmail.com
Published Online: 30-JUL-2018
DOI: http://dx.doi.org/10.7869/djo.379
Abstract
A 26-year-old female patient presented at our hospital with vision loss in her left eye. She gave a history of unilateral proptosis and on imaging was diagnosed as orbital schwannoma, for which the patient underwent orbital surgery. Post tumor resection, the patient complained of vision loss. On examination, her vision was no light perception. Fundus evaluation revealed central retinal artery occlusion (CRAO). Large Hollenhorst plaques were present. Carotid Doppler and cardiac evaluation were within normal limits. We hypothesised the presence of fat emboli similar as seen in fracture of long bones which may have caused occlusion of the central retinal artery. Thus, we recommend fundus examination to be done within 4 hours of any orbital tumor resection.
Keywords : CRAO, tumor, Schwannoma removal
Introduction

Central retinal artery occlusion (CRAO) is a sudden dramatic event for ophthalmologists and it presents as an acute ophthalmic emergency with an incidence of 1/10,000 outpatient visit.1,2 Hollenhorst plaques are the most common clinical finding, associated with CRAO. Management of CRAO requires immediate intervention. It can lead to visual acuity (VA) of counting fingers or less.3 Schwannomas are usually benign, slowly progressing, encapsulated tumors arising from Schwann cells in the peripheral nerve sheath, and may undergo malignant transformation. Rarely, schawannomas may have orbital extension and can cause vision loss.4 Here, we report a patient with vision loss due to CRAO post resection of schwannoma with orbital extension.

Case Report
We present a case of 26-year-old female patient who presented at our hospital with unilateral loss of vision in her left eye since 2 days after orbital surgery. Her left eye (LE) VA was no light perception, and right eye (RE) was 6/6.
She gave a history of unilateral progressive proptosis (without any visual complaints in the LE) since 1 year prior to surgery. Computed tomography scan of the orbit showed an intraconal mass near the optic nerve adhered to the superior ophthalmic fissure (Figure 1). A well defined heterogeneously enhancing lesion in the left retro bulbar space completely encasing the optic nerve with loss of fat planes between the lesion and adjoining recti muscles was seen. There was no evidence of ocular involvement or extension into extraorbital compartments.



On the basis of clinical and radiological findings, a provisional diagnosis of schwannoma involving the ophthalmic division of the trigeminal nerve was made. She underwent tumour resection by an oculoplastic surgeon. The procedure was done without complication as per the operative notes. Histological biopsy reports revealed to be benign tumour “Schwannoma”. Vision recorded on the opening of patch was no light perception (NLP). The patient was referred to us for further evaluation. Fundus examination revealed features of CRAO with presence of macular ischemia, ground-glass appearance of the retina, and Hollenhorst plaques seen at both inferior and superior retinal vessel (Figure 2). Optical coherence tomography showed lost foveal contour and loss of differentiation of retinal layers suggestive of ischemia (Figure 3). Carotid Doppler examination and ECG were normal.




Discussion
There are various reports describing systemic conditions associated with CRAO. Atherosclerosis of carotid arteries is an important and well-known risk factor for CRAO.5 Hollenhorst emboli also known as the fat emboli are the most common cause in routine clinical practice.
Rajabi et al6 described a case of CRAO following tumor resection. Their patient regained vision to 4/10 from no light perception following immediate ocular massage and anterior chamber paracentesis and systemic therapy with mannitol. They have not reported Hollenhorst plaques in the vessels. The mechanism, they proposed, may be the surgical manoeuvre causing compression of the eyeball leading to transient raised pressure on the central retinal artery and culminating in CRAO. Körner-Stiefbold also explained that retro bulbar masses might compress the central retinal artery and lead to arterial occlusion and decreased blood perfusion causing CRAO.7
Presence of fat embolus in the arteries in our case may be due to the similar mechanism as has been reported after orthopaedic surgeries or fracture of long bones. Two theories are postulated for the occurrence of fat embolism. First, there is the mechanical theory by Gossling et al8 which states that large fat droplets are released into the venous system deposit in the pulmonary capillary beds and travel through arteriovenous shunts to the systemic circulation. Microvascular lodging of the droplets produces local ischemia and inflammation. The biochemical theory states that hormonal changes caused by trauma and/or sepsis induce systemic release of free fatty acids as chylomicrons. Inflammatory mediators cause the chylomicrons to coalesce and create the physiologic reactions described above.
Hayreh et al stated that in CRAO, the ischemic retina could recover normal function from acute ischemia of 97 min. But, after that, the longer the ischemia, the more extensive and irreversible damage occurs.9 The exact retinal tolerance time when irreversible damage occurs is not yet known, but would appear to be no longer than 4?h.10 The rate of spontaneously recanalization of the artery is only about 15% with timely intervention.11,6
There is no approved modality to be effective in the treatment of CRAO.10 Some methods such as immediate ocular massage and anterior chamber paracentesis, use of drugs such as intravenous mannitol, systemic acetozolamide, topical anti glaucoma medication or inhalation of a mixture of 95% oxygen and 5% carbon dioxide (carbogen), all aimed to reduce intraocular pressure and improving blood flow to the eye. Other standard therapies include sublingual isosorbide dinitrate, systemic pentoxifylline and methylprednisolone. None of these therapies has been shown to be better than placebo.14 Without these modalities, <10% of patients can recover meaningful vision.12,13 Thus, it is one of the most important events in ophthalmology which needs immediate intervention.
Orbital schwannoma usually presents with proptosis with or without vision loss. There are reports of cases of solid cystic trigeminal schwannoma, with intraorbital extension through the superior orbital fissure, that was removed surgically and the patient regained vision within 2 weeks.12
We recommend that all patients undergoing tumour removal for any orbital tumour should undergo fundus examination immediately or within 4 hours of surgery to rule out the possibility of CRAO, as any delay in the diagnosis and lack of immediate intervention may cause severe irreversible vision loss as occurred in this case.

References 
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Navneet Mehrotra, Manish Nagpal, Hardik Jain, Avijit Vishnoi, Rakesh Juneja, Ashish JainCentral Retinal Arterial Occlusion Following Schwannoma Resection.DJO 2018;29:55-57
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Navneet Mehrotra, Manish Nagpal, Hardik Jain, Avijit Vishnoi, Rakesh Juneja, Ashish JainCentral Retinal Arterial Occlusion Following Schwannoma Resection.DJO [serial online] 2018[cited 2018 Sep 25];29:55-57. Available from: http://www.djo.org.in/articles/29/1/Central-Retinal-Arterial-Occlusion-Following-Schwannoma-Resection.html
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