Answer
When are flashes of light an emergency?
Medically reviewed by Mr Mohamed Mohyudin · Last reviewed 2026-07-06 · How review works
Treat these as an emergency
- New flashes that appear repeatedly over hours or days, especially in one eye
- Flashes together with a sudden shower of new floaters
- A dark shadow or curtain anywhere in your vision
- Any sudden drop in vision — seek emergency eye care now
What causes flashes of light
The eye is filled with a clear gel that sits against the retina. As the gel shifts or shrinks with age it can tug on the retina, and the retina reads that pulling as a brief flash of light — often at the edge of vision and most noticeable in the dark.
When flashes are usually harmless
A single brief flash that does not recur, in an eye with stable long-standing floaters and no other change, is usually part of age-related gel movement. Even so, new flashes that keep appearing deserve a prompt eye examination, because the common cause — the gel separating from the retina — can occasionally tear it.
The patterns that mean emergency
Repeated new flashes, a sudden shower of floaters, a shadow or curtain over vision, or any sudden drop in vision can mean the retina has torn or started to detach. A retinal tear can progress quickly, so these patterns need same-day assessment — not a routine appointment next week.
What happens at the emergency check
The examiner dilates your pupils and inspects the whole retina, looking for tears or detachment. It is painless. Most people are reassured and sent home the same day; if a tear is found, treatment can usually seal it before the retina detaches.
Frequently asked questions
Can flashes happen without a retinal problem?
Yes. Occasional flashes come from normal age-related gel movement, and some people notice them after rubbing their eyes. New flashes that keep recurring still need a prompt check.
Are flashes in both eyes at once less serious?
Flashes from the eye itself usually affect one eye. A shimmering zigzag in both eyes that fades over minutes is more typical of migraine aura. New one-sided flashes are the pattern to act on.
How quickly can a retinal tear become a detachment?
It varies, but detachment can follow within days. That is why the warning patterns need same-day assessment rather than watchful waiting.
Should I go to the emergency room or an optometrist?
Either is a good starting point for these warning signs — both can examine you or arrange a same-day dilated retinal examination. What matters is not waiting.
Trusted sources
This page reflects established clinical guidance. For further reading, consult these authoritative eye-health organisations: