Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services now if vision loss occurs with:
Facial drooping, arm or leg weakness, numbness, or speech trouble
New confusion, severe imbalance, or difficulty walking
A sudden, unusually severe headache
Loss of consciousness or a seizure
Vision that remains absent or severely reduced
A serious eye injury or chemical exposure
These symptoms can indicate a stroke or another emergency.
Do not drive yourself.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek urgent same-day medical or eye care for sudden vision loss in one eye, even if it has fully cleared.
You should also be assessed urgently for a curtain or shadow, new flashes with many floaters, or a painful red eye with halos, headache, nausea, or vomiting.
If you are over 50, temporary sight loss with a new headache, scalp tenderness, or jaw pain while chewing needs urgent assessment.
These can occur with inflammation of arteries supplying the eye.
3
Does any of this apply?
Book an appointment
Book a routine appointment if episodes recur after standing, severe blurring keeps returning, or your established migraine aura changes in frequency, duration, or appearance.
New visual symptoms should not automatically be assumed to be migraine.
Every sign above is quoted from the sofidex article on Temporary blindness. If you are not sure, err upward — it is always reasonable to be checked.