A true ocular emergency requiring treatment within minutes is:

Sudden loss of vision is indeed a true ocular emergency that requires immediate attention because it can indicate serious underlying conditions that may lead to permanent damage if not treated promptly. Conditions such as retinal detachment, central retinal artery occlusion, or acute glaucoma can cause vision loss in a matter of minutes and necessitate urgent medical intervention.

In contrast, while blurred vision and eye redness can certainly be troubling and may indicate the need for evaluation, they are generally not considered emergencies that require treatment within minutes. These symptoms can stem from various less acute causes, such as refractive error, dry eyes, or conjunctivitis, which typically allows for a longer timeframe for assessment and management.

Persistent headaches, while potentially distressing, likewise do not directly correlate with an immediate risk to vision that warrants urgent action. They might relate to a variety of conditions, some of which may require medical evaluation but aren't classified as ocular emergencies.

Thus, the urgency associated with sudden loss of vision makes it a critical situation in ophthalmic practice, emphasizing the need for swift diagnosis and treatment to preserve sight.