|Year : 2015 | Volume
| Issue : 1 | Page : 10-14
Optical coherence tomogram and demographic profile in central retinal artery occlusion: A South Indian study
YD Shilpa, BN Kalpana, Mohammed Sadiqulla
Department of Ophthalmology, Vitreo Retina Services, Minto Ophthalmic Hospital, Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India
|Date of Web Publication||29-Mar-2016|
Y D Shilpa
Department of Ophthalmology, Vitreo Retina Services, Minto Ophthalmic Hospital, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
Aim: To describe the demographic profile and optical coherence tomography (OCT) findings in patients with central retinal artery occlusion (CRAO). Materials and Methods: Thirty-eight patients with CRAO who presented to Vitreo Retina Department at Minto Ophthalmic Hospital between January 2009 and December 2013 were studied. All the patients underwent detailed ophthalmic examination including OCT and routine laboratory investigations. All patients were subjected to cardiac evaluation. Results: In our study, 27 (71%) were males and 11 (29%) were females. The average age of our patients was 44.8 years (range 25-65 years). Seven patients had diabetes, and six had hypertension. Seven (18%) patients had CRAO with sparing of the cilioretinal artery. History of smoking was present in 15 (56%) of males with an average duration of 16.9 years. OCT showed average central macular thickness of 288.2 mm in acute stage and 163.75 mm in chronic stage. Conclusion: CRAO had varying etiologies but had similar clinical findings and OCT features. In our study, smoking was found to be the most common association in males. CRAO was also seen in younger age groups too. In all cases, OCT in acute stage shows increased reflectivity of inner retina and a hyporeflective band and in chronic stage thinning of sensory retinal layer. OCT findings were similar irrespective of the etiology.
Keywords: Central retinal artery occlusion, demographic profile, optical coherence tomography
|How to cite this article:|
Shilpa Y D, Kalpana B N, Sadiqulla M. Optical coherence tomogram and demographic profile in central retinal artery occlusion: A South Indian study. Egypt Retina J 2015;3:10-4
|How to cite this URL:|
Shilpa Y D, Kalpana B N, Sadiqulla M. Optical coherence tomogram and demographic profile in central retinal artery occlusion: A South Indian study. Egypt Retina J [serial online] 2015 [cited 2019 Oct 20];3:10-4. Available from: http://www.egyptretinaj.com/text.asp?2015/3/1/10/179340
| Introduction|| |
Central retinal artery is an ocular emergency and is the ocular analog of cerebral stroke. It causes severe visual loss and has poor visual prognosis. 
Retinal artery occlusion (RAO) is mostly seen in the elderly with clinical findings suggestive of atheromatous emboli.  An estimated 0.85/10,000 patients over the age of 40 years are affected. 
Brown et al.  showed a nearly equal number of males and females involved while Greven et al.  showed a female predominance. An Indian study by Ratra and Dhupper has shown a predominantly male preponderance. 
Among earliest available reports, Von Graefe described an embolic central RAO (CRAO) in a patient with endocarditis and multiple systemic emboli as early as 1859.  Anterior segment examination is usually normal. In cases with concomitant carotid obstruction, rubeosis iridis may be observed due to neovascularization of the iris (ischemia).
The optical coherence tomography (OCT) images of ischemic retina in acute phase in most Western literature has shown a correlation with histopathological findings in ischemic retina. OCT demonstrates increased thickness and reflectivity in the inner layers of the affected retina. There are no available reports on optical coherence tomogram findings in RAO of varying etiologies among South Indian population. Hence, we intend to present the findings on time-domain OCT in our study group.
| Materials and Methods|| |
A retrospective analysis of case records of patients with CRAO visiting the Department of Ophthalmology in Minto Ophthalmic Hospital, Bangalore, from 2009 to 2014 was performed.
All the patients underwent ocular examination and occlusion of the central retinal artery was confirmed. Patients who had presented within 48 h of onset of symptoms underwent ocular massage and paracentesis under aseptic precaution. All patients underwent fundus photography and OCT. OCT was done using Stratus OCT TM Model 3000. OCT was done at presentation, 1 month, and 6 months. Blood investigations, erythrocyte sedimentation rate (ESR), C-reactive protein, homocysteine levels, random blood sugar, lipid profile, and carotid Doppler were ordered. All patients were subjected to cardiac evaluation along with two-dimensional (2D) echocardiography. All results were tabulated.
| Results|| |
A total of 38 cases with CRAO had presented to the Vitreo Retina Department at Minto Ophthalmic Hospital in 5 years. Among them 27 (71%) were males and 11 (29%) were females. The age group ranged from 25 to 65 years (median age 45 years). All the patients had unilateral involvement. The visual acuity ranged from counting fingers at 2 m to light perception. Right eye was involved in 20 (53%) cases and left eye in 18 (47%) cases. All of the 38 patients (100%) had relative afferent papillary defect (RAPD) at the time of examination.
Seven patients had CRAO with sparing of cilioretinal artery. Five male patients had ketoacidosis with suspected mucormycosis and these patients had complete ophthalmoplegia with CRAO. One male patient was diagnosed with liver hemangioma. One female patient had snake bite preceding loss of vision. One female patient was pregnant with amenorrhea 11 weeks. In males, 15 (56%) had history of chronic smoking with an average duration of 16.9 years [Graph 1 [Additional file 1]].
Carotid Doppler was performed on all patients of which 35 patients had normal, 2 patients had 15-30% obstruction, and one patient had 100% obstruction in carotid artery of ipsilateral side. The 2D echocardiography was normal in all the patients. Total cholesterol levels were within normal range in 35 patients and 3 patients it ranged between 229 and 267 mg/dl. All patients with diabetes had blood glucose levels in normal range. Blood pressures were normal in all cases. ESR ranged from 5 to 125 (average 25). C-reactive protein was 3.7 on an average. Homocysteine levels were normal with a range of 9.4-17.3 (average 13.4).
All patients were subjected to time-domain OCT. On OCT, a hyporeflective band between RPE and sensory retina and increased retinal thickness was observed in acute stage [Figure 1]. There was no correlation between visual acuity and macular edema. In chronic stage, OCT of these patients had thinning of sensory retinal layer.
|Figure 1: Optical coherence tomography image in retinal artery occlusion in acute phase. Increase in thickness of sensory retinal layer. Hyporeflective band between sensory retina and retinal pigment epithelium - Choriocapillary complex|
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| Discussion|| |
CRAO is an ocular emergency, which is a challenge to any ophthalmologist. Even today, there is no guideline for its treatment.  In our study, 71% were males similar to earlier report by Ratra et al. in contrast to Western literature which showed female preponderance. 
CRAO occurs in the mean age group of 60-65 years and predominantly affects males, our study showed a mean age of 44.8 years.
Over 75% of patients with CRAO suffer from generalized atheromatous disease, which is frequently associated with hypertension or diabetes mellitus, or both. 
In our study, 8 (21.1%) cases were diabetics and 6 (15.8%) were hypertensives. Systemic conditions were under normal limits in all cases.
In our study, 15 (55.6%) cases of males with CRAO had history of smoking. Smoking is a known risk factor for cardiovascular events. Concerning the risk profile, the cardiovascular risk factors for RAO are arterial hypertension, carotid artery diseases, cardiac rhythm disorders and cardiac valvular diseases, diabetes mellitus, hyperlipidemia, hyperuricemia, and chronic smoking. 
Inhalation of smoke results in absorption of nicotine with consequent release of adrenaline and noradrenaline. These bind to alpha-adrenergic receptors on vascular endothelium to cause muscle contraction and vasoconstriction. 
Five patients with diabetes were referred from physicians for decrease in vision and were suspected to have mucormycosis based on general examination and computed tomography scan reports. All the cases had unilateral, complete ophthalmoplegia with CRAO. Case reports of ocular mucormycosis with CRAO with ciliary artery occlusion have been reported in young and old. A 61 years male with uncontrolled diabetes reported in 1989.  Grewal et al. have reported a young patient 12 years male with diabetic ketoacidosis, orbital mucormycosis with orbital apex syndrome, and CRAO.  Mucormycosis causes necrotizing vasculitis by infiltrating walls of the blood vessel. Secondary thrombosis of vessel lumen occurs resulting in infarction.
Similar findings are reported in elderly male with uncontrolled diabetes and bilateral ophthalmic artery occlusion in a case of rhino-cerebro-orbital mucormycosis with complete ophthalmoplegia in the right eye and superior rectus palsy in the left eye. 
One of our patients was a 30-year-old female admitted in medical ward who complained of sudden loss of vision in right eye following snake bite (viper bite) was referred to ophthalmology department. On local examination, she had fang marks on the left toe with bleeding. She was conscious and well-oriented. Ocular examination showed right eye vision of counting fingers 2 m, RAPD, and fundus picture of CRAO and left eye was normal. Common ocular problems after snake bite can be due to neurologic or hematologic involvement. A case of CRAO following viper bite in a 23 years female in Maharashtra reported by Bhalla et al. in 2004.
Most of the demographic profile of these patients was comparable to international studies as mentioned in [Table 1]. We conducted time-domain OCT on all these patients with CRAO having varying etiologies and recorded the same which has not been reported in available literature to our knowledge.
|Table 1: Demographic profile in central retinal artery occlusion in various studies|
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In all patients with RAO, we observed similar OCT findings on time domain.
There is extensive inner retinal atrophy with disruption of the normal stratification of the inner retinal layers, loss of the normal foveal depression, and marked thinning of the retina in chronic CRAO.
Pathophysiologically systemic diseases may cause obstruction of the central retinal artery primarily through one or a combination of the following process embolism, vascular narrowing, thrombosis, arterial spasm, vascular narrowing caused by extravascular disease, and reduction in blood flow caused by carotid or ophthalmic artery obstruction, lowered systemic blood pressure, or elevated intraocular pressure. 
Ophthalmic artery is the first branch of internal carotid artery, hence emboli from the heart and carotid artery has a direct access to the eye. In patients presenting with CRAO, there is higher prevalence of systemic hypertension, diabetes mellitus, cerebrovascular accidents, and cardiac valvular disease. ,
The central retinal artery has no subsidiary access to other arteries and occlusion leads to immediate breakdown in all circulatory function.  The inner retina is supplied by central retinal artery while the outer retina gets its nourishment from choroidal circulation; hence, retinal artery obstruction selectively affects the inner retina.  This is followed by damage at the cellular level and typical intracellular edema. 
The most common causes of ophthalmic artery and/or CRAO are embolization from ulcerated plaques of the carotid artery and atherosclerotic occlusion of the internal carotid artery. 
In a series of 11 cases of CRAO published by Schmidt et al., the average central macular thickness was 372.5 with a range of 258-522 microns.  OCT findings in our case series, who presented within 10 days were comparable with this study, with an average constant maturity treasury of 362.4 (269-439) microns.
An afferent pupillary reaction is seen within seconds after central retinal artery obstruction. In the acute stage in the posterior pole, the retina becomes opacified and assumes a yellow-white appearance sparing the foveola.
OCT features are a reflection of the specific blood supply and the distinct changes in retinal histology that occur in chronic CRAO. Since the central retinal artery and its branches supplies only the inner retina, the atrophy and loss of stratification seen in chronic CRAO are limited to this layer of the retina and do not extend to the outer retina, which receives its blood supply from choroidal circulation. The disappearance of the foveal depression on OCT occurs because loss of the inner retina in chronic CRAO also involves the parafoveolar slope, leaving intact only the outer layers of the foveola itself. Therefore, macular OCT demonstrates milder retinal thinning and relative preservation of the foveal depression and stratification of the inner retinal layers. 
OCT shows a specific pattern in CRAO. Mostly these changes are confined to inner retinal layers. The retinal edema resolves with time on its own. Puliafito et al. was the first to state the presence of increased reflectivity of inner retinal layers and decreased reflectivity in outer retinal layers.  Salinas-Alamαn et al. proved the presence of hyporeflective band in all his three cases of CRAO and the OCT findings persisted at least 2 months. 
Retinal opacification is also present with acute ophthalmic artery obstruction. It is usually more pronounced both in the severity and in the extent of the area involved. The presence of a cherry-red spot with an acute ophthalmic artery obstruction is variable. With an ophthalmic artery obstruction, the presence or absence of a cherry-red spot is determined by the degree of choroidal hypoperfusion, the rapidity of onset of vascular compromise, and the duration of the ischemia.
Ophthalmoscopically observed whitening or opacification is due to intracellular swelling of the affected retina. The retinal opacification resolves within 4-6 weeks. Histopathologically, during the first 2 h after the occlusion of the artery, the neuronal cells in the inner retina become edematous. In the chronic cases, inner retinal atrophy and gliosis are noted in inner retina. 
| Conclusion|| |
OCT is an important imaging modality which has characteristic finding in CRAO and also helps in subsequent follow-up. OCT is increasingly being used in various retinal disorders due to its user friendliness and high-resolution imaging capabilities. It allows in vivo retinal cross-sectioning with resolution up to 5 microns. There was no correlation between visual acuity and macular edema. In the chronic stage, these patients had thinning of sensory retinal layer. Visual prognosis in CRAO remains poor. There is no generally agreed treatment for CRAO. OCT gives us an insight into the structural integrity of the ischemic macula and may be contributory to further research or prognosticating the final visual outcome.
RAO has a diverse etiology. It can vary from hypertension to even snake bite as in our case series. Identification of underlying pathology is essential during follow-up. Most of our male patients were smokers. This may pose as a risk factor. However, larger studies are warranted to postulate the same.
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Conflicts of interest
There are no conflicts of interest.
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