Answers

1. Pale white retinal background with cherry red spot at the fovea, thread like attenuated blood vessels with cattle-track appearance [Figure 1].
2. Grade II hypertensive retinopathy with arteriovenous crossing changes [Figure 2].
3. Routine blood investigations were normal except for raised erythrocyte sedimentation rate which was 56 mm at the end of 1 h and positive C-reactive protein. Rest of the blood investigations such as blood sugar, lipid profile, prothrombin time, bleeding time and clotting time was normal. Two-dimensional-echocardiography was done, which showed good systolic and diastolic function with no valvular pathology. Bilateral carotid Doppler was done, which showed a plaque of 5.2 × 1.2 mm size in the posterolateral aspect of left carotid artery in the carotid bulb [Figure 3].

Figure 3: Carotid Doppler left common carotid artery Click here to view

Discussion

A central retinal artery occlusion is a blockage of the main artery to the retina. Like all nervous tissue, the retina requires large quantities of oxygen delivered by the bloodstream in order to function properly. Interruption of blood supply even for a few minutes impairs vision, and unless the blood supply is restored within 90 min, permanent damage to the retina with loss of part of the visual field results. In many instances, it is impossible to ascertain the exact pathophysiologic process responsible for central retinal artery obstruction. ^[1] The main causes are emboli, intraluminal thrombosis, vasculitis, spasm, hypertensive arterial necrosis, dissecting aneurysm. ^[2],[3] These causes are intimately related to associated systemic abnormalities like diabetes mellitus (25%) ^[1] hypertension (66%) and cardiac valvular disease (25%). ^[4] The emboli are visible within the retinal arterial system in about 20-40% of eyes with central retinal artery occlusion. Emboli can originate from any part of the arterial system. The most common is cholesterol emboli from atherosclerotic deposits in carotid arteries. The other emboli are fibrin platelet thrombus and calcific emboli which usually originate from cardiac valves and cause more severe obstruction. Abnormalities in the cardiac valves or circulation as seen in infective endocarditis should be ruled out in every case of central retinal artery occlusion. Embolus from the heart is the most common cause of central retinal artery occlusion in patients younger than 40 years. In our case, the carotid Doppler revealed a plaque in left-sided carotid bulb from there it might have gone to central retinal artery. There are various triggering factors for atherosclerosis; in our case, the patient was found to be hypertensive. Treatment of central retinal artery occlusion can be categorized as conservative (ocular massage, pharmacological treatment, anterior chamber paracentesis) or invasive (catheterization of the proximal ophthalmic artery through the femoral artery with the infusion of thrombolytic agents). However, to date, no satisfactory therapy is available for patients with this disorder ^[5],[6] and in most cases therapy is not successful.

Conclusion

Central retinal artery occlusion is an ophthalmic emergency, causing acute painless loss of vision. There are various triggering factors for atherosclerosis; in our case, the patient was found to be hypertensive.