Floaters and flashes
- Clinical approach
New floaters and flashes are usually the vitreous gel peeling off the retina. It can tear the retina, so each new episode needs a dilated exam soon.
What it is
Floaters are shadows cast on the retina by opacities in the vitreous; flashes (photopsia) are the retina being pulled. Their sudden onset in an adult is usually a posterior vitreous detachment, which becomes common after 50 and earlier in short-sighted people. Its danger is a retinal tear, found in a minority of acute cases, which can progress to a retinal detachment. Long-standing, unchanged floaters are usually harmless.
Red flags
- A shower of new floaters or a sudden large increase.
- A shadow or curtain in the peripheral vision: retinal detachment.
- Reduced visual acuity.
- High myopia, previous detachment in the other eye, recent eye surgery or trauma.
- Pigment cells or blood in the vitreous on slit lamp exam: high chance of a retinal tear.
Step-by-step approach
- Ask when it started, whether the floaters are new or a change, and whether there are flashes or a shadow.
- Distinguish migraine aura: zigzag lights in both eyes spreading over about 20 minutes, often followed by headache.
- Measure visual acuity and test the peripheral field of each eye.
- Check the red reflex: vitreous haemorrhage dulls it.
- Refer for a dilated exam of the peripheral retina; the direct ophthalmoscope cannot exclude a peripheral tear.
Floaters and flashes: what they mean
| Picture | Likely cause | Urgency |
|---|---|---|
| New floaters and flashes, no shadow | Posterior vitreous detachment | Dilated exam within about a day if red flags, otherwise within days |
| Shower of floaters, dark haze | Vitreous haemorrhage, possible retinal tear | Same day |
| Curtain or shadow, reduced vision | Retinal detachment | Same day; emergency if central vision is still normal |
| Zigzag lights in both eyes, then headache | Migraine aura | Not urgent if typical |
| Old floaters unchanged for years | Vitreous condensations | Routine |
Keys to the differential
- A posterior vitreous detachment is a normal ageing event, but a symptomatic one needs a peripheral retina exam because a tear may be silent.
- A retinal tear found before detachment is treated with laser or cryotherapy in the clinic.
- Flashes that persist in one eye are retinal; flashes seen with either eye closed are cortical (migraine).
Next step / Initial management
- New floaters or flashes: dilated retinal exam by ophthalmology, the same day if there is a shadow, reduced vision or a shower of floaters, otherwise within a few days.
- Retinal tear: laser retinopexy or cryotherapy promptly to prevent detachment.
- Retinal detachment: same-day referral for surgery.
- Uncomplicated posterior vitreous detachment: explain the warning symptoms (more floaters, flashes, a shadow) and to return at once if they appear; a follow-up exam is often arranged in the following weeks.
Test yourself
Think of the answer, then tap the question to see it.
What is the main risk of an acute posterior vitreous detachment?
A retinal tear, which can progress to a retinal detachment.
Which symptom with floaters means a same-day referral?
A shadow or curtain in the vision, reduced acuity, or a sudden shower of floaters.
Why is the direct ophthalmoscope not enough to exclude a retinal tear?
Because tears are usually in the peripheral retina, which needs a dilated exam with indirect ophthalmoscopy or a slit lamp lens.
Connections
Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.
Sources: Posterior Vitreous Detachment (StatPearls Publishing (NCBI Bookshelf), 2026); Retinal Detachment (StatPearls Publishing (NCBI Bookshelf), 2024); Vitreous Hemorrhage (StatPearls Publishing (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.