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
A chemical splash to the eye is an emergency.
Rinse the eye immediately with plenty of clean lukewarm water and seek emergency help.
Sudden vision loss, major eye trauma, or a foreign object embedded in the eye also requires emergency care.
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 assessment if you have:
Moderate or severe eye pain
Reduced, blurred, or distorted vision
Marked sensitivity to light
A dark red or purple area on the white of the eye
A painful red eye while wearing contact lenses
Increasing redness or swelling
Recent eye surgery or an eye injury
Headache, nausea, or coloured halos around lights with a red eye
Do not wait for redness or pain to develop.
3
Does any of this apply?
Book an appointment
Arrange a routine eye examination if this is your first unexplained episode of eye redness, if the redness keeps returning, or if it is not improving as expected.
Routine follow-up is also appropriate if episodes affect both eyes or occur with ongoing joint swelling, rashes, bowel symptoms, mouth ulcers, or other signs of inflammation.
Every sign above is quoted from the sofidex article on Episcleritis. If you are not sure, err upward — it is always reasonable to be checked.