###Rationale: Answer: d) Central retinal artery occlusion (KANSKI 8th ED, P-552)RETINAL ARTERY QCCLUSioNEtiology* Atherosclerosis - related thrombosis at the level of lamina cribrosa - most common cause* Emboli from carotid artery and cardiac origin> Cholesterol emboli (Hollenhorst plaque)> Calcium emboli> Platelet fibrin emboli - cause retinal ischemic attacks* Retinal arteritis - Polyarteritis nodosa, SLE, Wegener's granulomatosis, Scleroderma* Angiospasm, Raised IOP, Thrombophilia* Rare causes - Sickle cell anemia, retinal migraine, Oral contraceptives, polycythemia, Antiphospholipid syndromeClinical features* More common in males; Mean age at onset - 60 years* Usually unilateral* Central retinal artery occlusion (CRAO)> Obstruction at the level of lamina cribrosa> Sudden painless loss of vision> Markedly reduced visual acuity> Absent direct pupillary reflex - Total and profound afferent pupillary defect (APD) (amaurotic pupil)> Marked narrowing of retinal arteries and mild narrowing of retinal veins> The orange reflex from the intact choroid stands out at the thin foveola, in contrast to the surrounding pale retina, giving rise to a 'cherry-red spot' appearance> Milky white retina> Cherry red spot in the center of macula> Cattle truck appearance - segmentation of blood column in retinal vein> Atrophic changes - grossly attenuated thread like arteries and consecutive optic atrophy> FFA - delay in arterial filling and masking of choroidal vasculature due to retinal edema* Branch retinal artery occlusion (BRAO) - Obstruction at a bifurcationTreatment* No effective treatment available currently* Immediate lowering of IOP by> Intermittent ocular massage> IV mannitol or acetazolamide> Paracentesis of anterior chamber* Inhalation of carbogen or Meduna's Mixture (95 % O2 and 5 % CO2) - to relieve angiospasm* Steroids in cases of giant cell arteritisComplication - Neovascular glaucoma

###Answer: OPTION D IS CORRECT.
###Question: A 56 year old woman came to the emergency room 3 hours after visual loss in the right eye. Visual sensitivity limits to light perception in the right eye. Examination reveals pupillary defect whereas anterior surface of both eye are normal. Fundus examination shows a red lesion with pale retina. Probable diagnosis
###Options:
A. Central vein occlusion
B. Proliferative diabetic retinopathy
C. Background diabetic retinopathy
D. Central retinal artery occlusion
