A 75-year-old man with DM and HTN experiences acute monocular blindness that resolves after 1 hour. What is the most likely diagnosis?

The scenario describes a 75-year-old man with diabetes mellitus (DM) and hypertension (HTN) who experiences acute monocular blindness that resolves after an hour. The most likely diagnosis in this case is amaurosis fugax.

Amaurosis fugax is characterized by transient monocular vision loss due to temporary ischemia of the retina, commonly associated with systemic vascular conditions such as diabetes and hypertension. This condition often results from embolic events or decreased blood flow, affecting the retina momentarily. The key aspect of amaurosis fugax is that the vision loss typically resolves swiftly, which aligns perfectly with the symptom of blindness lasting for just one hour in this patient.

This condition can be a warning sign of underlying vascular issues, pointing towards a higher risk of stroke or other significant vascular events in the future. The patient's age and existing health conditions further supplement the likelihood of amaurosis fugax.

The incorrect options are differentiated in terms of their clinical presentations and duration of symptoms. For instance, giant cell arteritis typically presents with persistent loss of vision and associated systemic symptoms, optic neuritis is usually characterized by pain and is often linked to multiple sclerosis, and a lacunar infarct would usually lead to more permanent deficits rather than transient blindness.