This page reveals the answer
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Five progressive clues
These are the case findings in their original reveal order, moving from the broader presentation to the most discriminating evidence.
Clue 1
A 68-year-old man watching a baseball game finds the vision in his left eye switches off like a light — painless, total and instantaneous. He arrives 90 minutes later still able to see only a dim glow on that side.
Clue 2
He has had two brief episodes of transient vision loss in the same eye over the past month, each lasting about five minutes with full recovery. He has hypertension, hyperlipidaemia and atrial fibrillation, and stopped taking apixaban three weeks ago because of the cost.
Clue 3
Visual acuity is counting fingers at one foot on the left and 20/25 on the right. There is a brisk left relative afferent pupillary defect. The anterior segment is quiet and intraocular pressure is 15 mmHg in both eyes.
Clue 4
Dilated fundus exam of the left eye shows a diffusely pale, opacified posterior pole with markedly attenuated, segmented arterioles. OCT shows thickening and hyperreflectivity of the inner retinal layers with shadowing of the outer retina.
Clue 5
Against the whitened background the fovea stands out as a distinct reddish-orange spot, because the retina there is thin enough for the underlying choroidal circulation to show through.
Diagnosis
Central Retinal Artery Occlusion
Why the diagnosis fits
Sudden, painless, profound monocular vision loss with a relative afferent pupillary defect and inner-retinal whitening points to abrupt interruption of the retinal arterial supply, most often embolic. The red foveal spot is not a lesion — it is normal choroidal colour showing through the only part of the retina too thin to become opaque. Retinal opacification with attenuated arterioles is what separates this from an acute optic neuropathy, and it is a stroke equivalent that needs emergent cerebrovascular workup.
Educational reference
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Open the clinical referenceFor education and entertainment only. This fictional case is not medical advice and does not replace supervised clinical training, diagnosis, or treatment.