Eye floaters and flashes: when to worry (UK guide)

Floaters and flashes are among the most common eye symptoms in UK adults over 45, and the vast majority are harmless. But they are also the classic warning signs of retinal detachment, a sight-threatening emergency. This guide explains how to tell the two apart.

What are floaters?

Floaters are small shapes — dots, cobwebs, threads, rings — that drift across your vision and move when you shift your gaze. They are shadows cast on the retina by tiny opacities inside the vitreous, the gel that fills the back of the eye. Most floaters are age-related and appear as the vitreous gel liquefies and shrinks with time.

Occasional new floaters that fade over weeks are almost always due to a benign process called **posterior vitreous detachment (PVD)**, which affects around two-thirds of people by age 70.

What are flashes?

Flashes are brief arcs or sparks of light, most obvious at the edge of vision and in a dark room. They are caused by the vitreous tugging on the retina as it separates. They differ from migraine aura, which produces jagged, coloured, zigzag patterns lasting 20–30 minutes and affecting both eyes at once.

The four warning signs — same-day review needed

Attend an eye casualty or your nearest urgent eye clinic today if you notice any of the following:

1. **A sudden shower of new floaters** — dozens of them at once, not just one or two

2. **New or increasing flashing lights**

3. **A dark curtain, shadow or veil** creeping across your vision from any direction

4. **Blurred vision** that came on suddenly in one eye

These symptoms may indicate a retinal tear or detachment, and treatment within 24–48 hours preserves central vision.

Retinal tears and detachment

As the vitreous separates, it can pull hard enough to tear the retina. A tear alone is treated with laser (retinopexy) as a 10-minute outpatient procedure and prevents progression. If fluid tracks under the retina, a full detachment occurs and needs urgent surgery — pneumatic retinopexy, vitrectomy or scleral buckling — usually within 24 hours to protect central vision.

Risk is higher in patients who are:

- Short-sighted (myopic), especially above −6 dioptres

- Post-cataract or post-YAG laser (see YAG laser capsulotomy)

- Post-eye trauma

- Aged 55–75

- With a family history of retinal detachment

Harmless floaters: what to do

If a specialist has confirmed a normal retina and only PVD or age-related floaters, no treatment is needed. Most floaters settle down within 3–6 months as the brain learns to ignore them. Vitrectomy for floaters is possible but rarely justified because of the operative risk.

How the assessment is done

A proper floaters-and-flashes assessment requires:

- Full dilated examination of the retina to the far periphery

- Slit-lamp biomicroscopy

- OCT scan of the macula in selected cases

You should not drive home immediately after dilation as vision is blurred and light-sensitive for 4–6 hours.

Migraine, blood pressure and other causes

Not every flash is a retinal problem. Consider:

- **Ocular migraine** — 20–30 minute zigzag pattern in both eyes, may have headache

- **Postural hypotension** — brief black-out with getting up quickly

- **Optic nerve inflammation** — steady blur or pain on eye movement (needs neurology assessment)

If in doubt, treat any new symptom as urgent and be assessed in person.

Next steps

If you have new floaters or flashes today, attend your nearest eye A&E, contact NHS 111, or if you would prefer a same-week private assessment, book a consultation with my London practice or call **020 3137 3237**. Same-day retinal review is arranged for anyone with warning symptoms.