Eye Floaters and Flashes of Light: When to Seek Emergency Care
Most eye floaters are harmless. But a sudden increase in floaters, flashes of light, or a shadow in your vision can signal a retinal tear or detachment — a true eye emergency.
Updated · Dr. Ema Hazra
Seeing small specks or threads drifting across your vision is common and, in most cases, completely harmless. However, certain changes to floaters or flashes of light are medical emergencies that require same-day evaluation.
What floaters are
Floaters are shadows cast on your retina by debris within the vitreous — the clear, gel-like substance that fills the back of your eye. As you age, the vitreous gradually liquefies and shrinks, and collagen fibres clump together. You see them most clearly against a bright background (a white wall, a blue sky).
Most people over 40 will develop floaters at some point. They are usually more noticeable when they first appear and become less bothersome over time as the brain adapts to ignoring them.
Posterior vitreous detachment (PVD)
The most common cause of a sudden new floater is posterior vitreous detachment — when the vitreous pulls away from the retina as a natural part of aging. PVD typically occurs between ages 50 and 75. It causes:
- A new ring-shaped or large floater
- Brief flashes of light, especially in peripheral vision
- Symptoms that are most noticeable in the first few weeks
PVD itself is not dangerous, but it carries a 1–3% risk of causing a retinal tear as the vitreous detaches. This is why a new PVD should be evaluated by an optometrist or ophthalmologist promptly — even if symptoms seem mild.
When floaters and flashes are an emergency
Go to an eye emergency clinic or hospital emergency department immediately if you experience:
- A sudden shower of many new floaters (not just one or two)
- Flashing lights that persist or recur, especially in peripheral vision
- A dark curtain, shadow, or veil encroaching on any part of your vision
- Sudden significant blurring of vision in one eye
These symptoms can indicate a retinal tear or detachment — a condition where the retina peels away from the back wall of the eye. Without prompt treatment, a detachment can progress to permanent vision loss.
Retinal detachment: what happens and why urgency matters
When the retina detaches, it loses its blood supply. The longer it remains detached, the more photoreceptor cells die. If the detachment reaches the macula (the central region responsible for sharp, detailed vision), the outcome is significantly worse even after successful surgical repair.
A retinal tear caught before detachment occurs can often be sealed with in-office laser treatment within days — a quick, effective procedure with excellent outcomes.
What to do
| Symptoms | Action |
|---|---|
| A few small, stable floaters you've had for a while | Normal — monitor |
| New floaters after age 50, no flashes | See an optometrist within 1–2 weeks |
| New floaters with brief flashes | See an optometrist or ophthalmologist within 24–48 hours |
| Shower of new floaters, persistent flashes, or curtain in vision | Go to emergency care immediately |
In Ontario, many optometry clinics offer same-day urgent appointments for sudden changes in vision. Call your optometrist first — they can assess and refer directly to an ophthalmologist if surgery is needed.
Floaters that are not emergencies
Most chronic, long-standing floaters are benign. Small, stable floaters that have been present for months or years and are not accompanied by other symptoms do not require emergency care. Mention them at your next routine eye exam. There is currently no widely-available, proven treatment for benign vitreous floaters; laser vitreolysis exists but is not commonly performed in Ontario and carries its own risks.
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Book an appointment →Frequently Asked Questions
- What causes eye floaters?
- Floaters are caused by clumps or strands of collagen within the vitreous — the gel-like fluid that fills the eye. As the vitreous liquefies and shrinks with age, these particles cast shadows on the retina, which you perceive as dots, threads, or cobwebs that drift when you move your eyes.
- Are eye floaters dangerous?
- Most floaters are harmless and caused by age-related changes in the vitreous gel (posterior vitreous detachment). However, a sudden onset of many new floaters — especially with flashes of light or a curtain/shadow in your vision — can indicate a retinal tear or detachment, which requires emergency treatment.
- What causes flashes of light in the eye?
- Flashes of light (photopsia) occur when the vitreous tugs on the retina, mechanically stimulating it. This commonly happens during posterior vitreous detachment. Persistent flashes, especially when accompanied by new floaters, can indicate the vitreous has caused a tear in the retina.
- What are the warning signs of a retinal detachment?
- Warning signs include: a sudden shower of new floaters, flashing lights (especially in peripheral vision), a dark curtain, shadow, or veil that appears to move across your vision, and sudden blurred vision. Any of these symptoms require same-day emergency evaluation — either at an eye emergency clinic or hospital emergency room.
- What is the treatment for a retinal tear or detachment?
- A retinal tear without detachment is usually treated with laser photocoagulation or cryotherapy (freezing) in a clinic setting. A retinal detachment requires surgery — typically pneumatic retinopexy, scleral buckling, or vitrectomy. Outcomes are significantly better when treated promptly before the macula is involved.
Author
Dr. Ema Hazra, OD — Pending clinical review
Optometrist, Spadina Optometry
A Toronto native, Dr. Ema Hazra earned her Doctor of Optometry from the University of Waterloo in 2018 and returned to Spadina Optometry — where she had previously interned — bringing experience from an ocular disease externship at Eye Associates of Pinellas in Florida alongside leading ophthalmologists specializing in glaucoma, macular degeneration, and retinal disease. Her clinical interests include myopia control, specialty contact lenses, dry eye disease, and refractive surgery, and she is passionate about providing comprehensive care for patients of all ages, especially children.