Flashes & Floaters
Written 16th July 2020 - Last Update 23rd July 2026
Flashes & Floaters
Floaters
Dark spots caused by opacities in the vitreous casting shadows on the retina, or light bending at the junction between pockets of fluid in the vitreous. Often described as flies, cobwebs or worms, more pronounced against light backgrounds.
Causes:
- Vitreous debris from infection, inflammation or haemorrhage
- Age-related vitreous condensation (collagen fibre aggregation)
- Haemorrhage of retinal vessels into the vitreous — usually from diabetic retinopathy
Flashes
Perception of light without an external stimulus, from mechanical stimulation of the retina by vitreous traction. More noticeable in dim lighting, usually in the temporal visual field.
Triage — this is the key clinical decision
Patients presenting with new flashes and/or floaters need ophthalmological assessment to exclude a retinal tear or detachment, which can progress to significant, permanent visual loss if missed.
- New-onset flashes/floaters → same-day fundoscopy/ophthalmology assessment to rule out retinal tear or detachment
- Long-standing, stable flashes and floaters → non-urgent ophthalmology review
A 2026 AJGP article (“‘Spots’ the sign”) reinforces this same-day threshold: a sudden shower
of new floaters, a flash of light, or a curtain/shadow across the visual field are the
classic retinal-detachment red flags that should not wait for a routine referral — see
retinal-detachment.md and retinal-tear.md.
Differential diagnosis
Flashes
| Category | Cause | Distinguishing features |
|---|---|---|
| Ophthalmic | Posterior vitreous detachment | See posterior-vitreous-detachment.md |
| Ophthalmic | Retinal tear / retinal detachment | Same-day referral (above) |
| Ophthalmic | Optic neuritis | Flashes (photopsia) with eye movement, retrobulbar pain |
| Vascular | Vertebrobasilar TIA | — |
| Vascular | Postural hypotension | Bilateral, transient dimming of vision with light-headedness |
| Neoplastic | Occipital tumour | — |
| Congenital/functional | Migraine (visual aura) | Scintillating scotoma, coloured lights, bilateral, resolves in 5–30 min, followed by headache |
Floaters
| Cause | Notes |
|---|---|
| Vitreous haemorrhage | — |
| Posterior vitreous detachment | See posterior-vitreous-detachment.md |
| Retinal detachment | Same-day referral (above) |
| Vitritis | Inflammatory |
| Tear film debris | Benign, mobile with blinking |