What causes blurred vision?

The change may affect one eye or both, come and go, or remain present. A dry, irritated eye can make the surface of the eye uneven, while dehydration, tiredness, contact lens problems, or an untreated eye prescription can make vision seem hazy. Fluctuating blood sugar can temporarily alter the eye's focusing system; low blood sugar may also cause blurred vision with sweating, shaking, hunger, or confusion. Hypertension can affect blood vessels supplying the eyes.

Migraine may cause temporary visual changes such as shimmering lights, zigzag shapes, or a blurred area, sometimes before head pain. Blurred vision can also occur with a retinal problem, glaucoma, or another eye condition, so the timing and accompanying symptoms matter. A symptom page on [Blurred Vision](/symptoms/blurred-vision/) gives more detail.

If the change is mild and clears after blinking or resting, remove contact lenses, avoid driving until vision is clear, and arrange an eye or primary-care assessment if it returns. Note whether one or both eyes are affected, how suddenly it began, and any headache, eye pain, redness, weakness, or change in speech. Do not change diabetes or blood-pressure medicines without clinical advice. Conditions such as [Dry Eye](/conditions/dry-eye/), [Hypoglycaemia](/conditions/hypoglycaemia/), and [Type 2 Diabetes](/conditions/type-2-diabetes/) may be relevant depending on the pattern.

Seek emergency help for sudden loss or marked worsening of vision, a dark curtain or shower of new floaters, severe eye pain, or vision change after an eye injury. Call emergency services immediately if blurred vision starts with facial drooping, arm weakness, trouble speaking, severe imbalance, or a sudden severe headache, because these can be signs of [Stroke](/conditions/stroke/). A new visual disturbance with a severe headache may also need urgent assessment; [Migraine](/conditions/migraine/) is one possible cause, but it should not be assumed without considering red flags.

Ask: Is the problem coming from the eye surface, the lens, the retina, or a wider health issue? Do I need an eye examination or blood-glucose and blood-pressure checks? Which symptoms should make me seek emergency care?