GPAtlas🧭 When to suspect
Flashes and floaters are among the most common eye symptoms in primary care.
• Floaters are specks, dots, threads or cobwebs that drift across the vision and are most obvious against a plain bright background.
• Flashes (photopsia) are brief, lightning-like streaks of light, typically in the peripheral field and often noticed in dim light or with eye movement.
The usual cause is a posterior vitreous detachment (PVD) – the age-related shrinkage and separation of the vitreous gel from the retina. It is benign in itself.
PVD is common (rising from around a quarter of people in their 50s to the great majority by their 80s), and more frequent or earlier:
• In myopia (short-sightedness)
• After cataract surgery
• After ocular trauma
The whole point of the consultation is what PVD can hide:
• As the vitreous peels away it can tear the retina.
• An untreated tear can progress to a sight-threatening rhegmatogenous retinal detachment (RRD).
• In UK community series roughly 1 in 10 people with an acute symptomatic PVD already has a retinal tear.
So you must:
• Recognise the benign pattern
• Never miss the sight-threatening one
• Refer at the right speed – every new presentation needs a dilated retinal examination
| Cause to consider | Features that point to it |
|---|---|
| Posterior vitreous detachment (PVD) | • New floaters with brief peripheral flashes • Painless • Vision otherwise preserved • Older, myopic or post-cataract eye |
| Retinal tear or retinal detachment (RRD) | Sudden shower of floaters, persistent flashes, a curtain, shadow or veil crossing the field, or a drop in vision – sight-threatening. |
| Vitreous haemorrhage | • Sudden floaters, "smoke" or cobwebs ± reduced vision • Think retinal tear, diabetic retinopathy or anticoagulation – a warning sign of an underlying tear |
| Migraine aura | Gradually expanding zig-zag or shimmering lights in both eyes lasting 20–60 minutes, often followed by headache – not floaters. |
|
🧠 Clinical pearl • The quickest way to separate migraine aura from a retinal cause is to ask about both eyes and eyes closed. • Aura is cortical: it affects the same side of the field in both eyes, marches and expands over minutes, and lasts up to an hour. • Aura is still "seen" with the eyes shut – often resolving just as a headache begins. • Vitreoretinal flashes are the opposite: one eye, momentary, peripheral, and provoked by eye movement. • If the patient can see it with both eyes closed, think brain, not eye. |
Source: College of Optometrists · Royal College of Ophthalmologists
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