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