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. 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, and after ocular trauma. It is benign in itself.
The whole point of the consultation is what PVD can hide: as the vitreous peels away it can tear the retina, and 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. The key skill is therefore to recognise the benign pattern, never miss the sight-threatening one, and 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 / 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. |
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🧠 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, lasts up to an hour, and 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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