1. What you can do right now
Quick help with visual disturbances
- FAST test if a stroke is suspected: a drooping corner of the mouth, a speech disturbance, weakness in one arm? Call 112 immediately (in the US: 911).
- Sudden vs. gradual: a sudden loss of vision, flashes of light with a shower of soot-like floaters or a curtain across the field of vision → the ophthalmic emergency department.
- Test double vision: cover one eye – do the double images disappear? Then binocular (often neurological). Do they persist? Then monocular (an eye cause).
- With diabetes: check your blood sugar. Strongly altered values can cause temporary blurring.
- Screening: from age 40, an annual ophthalmic check-up (glaucoma). With diabetes, a fundus check at least once a year.
EMERGENCY: get medical help immediately!
A sudden loss of vision in one eye (a "curtain", a black spot) – suspicion of retinal detachment or a vascular occlusion. Sudden double vision with one-sided weakness or a speech disturbance – suspicion of stroke (FAST). Flashes of light with a "shower of soot" – suspicion of retinal detachment. Acute severe eye pain with reduced vision, halos around lights, nausea – suspicion of an acute glaucoma attack. Temporary blindness lasting seconds to minutes (amaurosis fugax) – a sign of a TIA or carotid stenosis.
2. Understanding visual disturbances – what happens in the body?
Visual disturbances mean any change in the ability to see – from slight blurring through double vision and blurred vision to a sudden loss of vision. Visual disturbances are a symptom, not an illness in their own right. The causes range from harmless refractive errors to life-threatening conditions like stroke.
The most important forms
Blurred vision: the most common form. Causes: refractive error, dry eyes, cataract, diabetes, high blood pressure.
Double vision (diplopia): seeing two images of one object. Important: monocular (also when one eye is covered – an eye cause) vs. binocular (disappears when covered – a sign of a neurological cause).
Visual field loss (scotoma): an area in which nothing is perceived. One-sided losses (hemianopia) point to a stroke or to diseases of the visual pathway.
Shimmering, flashes of light, aura: typical of migraine with aura. Flashes of light can, however, also point to retinal detachment.
Distorted vision (metamorphopsia): straight lines appear crooked – a typical sign of age-related macular degeneration.
Mouches volantes ("floaters"): dots or threads in the field of vision. Mostly harmless. Suddenly new or increasing floaters with flashes of light should be assessed by an ophthalmologist immediately.
Colour vision disturbances: can point to diseases of the retina, of the optic nerve (optic neuritis), to poisoning or to medication side effects.
A simple self-test: monocular or binocular?
With double vision: cover one eye. Do the double images disappear? Then binocular – suspicion of a neurological cause, a cranial nerve palsy or thyroid eye disease. Do the double images remain? Then monocular – the cause is in the eye itself (cataract, a corneal disease). Important for the right point of contact.
3. Common causes of visual disturbances
3.1 Eye diseases
Refractive error: short-sightedness (myopia), long-sightedness (hyperopia), astigmatism, presbyopia – by far the most common cause.
Dry eyes (sicca syndrome): fluctuating blurred vision, burning, a foreign-body sensation. Intensified by screen work, air conditioning, medications, the menopause.
Cataract (grey star): a clouding of the lens of the eye – a gradual worsening of vision, sensitivity to glare. Well treatable by surgery.
Glaucoma (green star): damage to the optic nerve from raised intraocular pressure – a slow loss of the visual field, often unnoticed for a long time. An acute glaucoma attack is an emergency.
Age-related macular degeneration (AMD): a gradual worsening of central visual acuity, distorted vision – the most common cause of severe visual impairment in old age.
Retinal detachment: an emergency – flashes of light, many new "floaters", a black curtain across the field of vision.
Optic neuritis: inflammation of the optic nerve, often in the context of multiple sclerosis – worsening vision, pain on eye movement, colour vision disturbances.
Eye inflammations: conjunctivitis, uveitis, keratitis.
3.2 Systemic and neurological
Stroke / TIA: one-sided visual field loss, double vision, temporary blindness in one eye (amaurosis fugax). An emergency.
Migraine with aura: shimmering, jagged lines, scotomas – usually increasing over 5–20 minutes, followed by a headache.
High blood pressure: hypertensive crises can cause acute visual disturbances. Chronic high blood pressure also damages the retinal vessels in the long term.
Diabetes: diabetic retinopathy is one of the most common causes of loss of vision in working-age people. Acute blood sugar swings can also cause temporary blurring.
Giant cell arteritis (temporal arteritis): in older people – headaches, jaw claudication, sudden one-sided loss of vision. An emergency, because the other eye is at risk.
Multiple sclerosis: optic neuritis is possible as a first symptom.
Thyroid diseases: thyroid eye disease in Graves' disease – protrusion of the eyes, double vision, compression of the optic nerve.
4. Sudden or gradual?
With visual disturbances, the most important diagnostic question is how quickly they developed – it distinguishes emergencies from changes that can be assessed on a planned basis.
| Feature | Sudden visual disturbance | Gradual visual disturbance |
|---|
| Time course | Seconds to hours | Weeks to years |
| Typical causes | Stroke, retinal detachment, glaucoma attack, migraine aura | Refractive error, cataract, AMD, diabetic retinopathy, glaucoma |
| Point of contact | The ophthalmic emergency department or 112 (in the US: 911) | The ophthalmic practice – plannable |
| Diagnostic focus | Immediate emergency diagnostics (CT, intraocular pressure, fundus) | Eye test, OCT, fundus, lab if needed |
Also important: one eye or both? One-sided visual disturbances are often a sign of a local problem in the eye or in the area of the visual pathway (e.g. carotid stenosis, optic neuritis). Bilateral visual disturbances point rather to systemic causes (migraine aura, a stroke in the visual centre, a diabetes-related change in the lens).
5. What really helps
Treatment according to cause
Refractive error: glasses or contact lenses, refractive surgery if needed.
Dry eyes: tear substitutes, eye care.
Cataract: surgery with a lens implant – one of the most common and safest operations of all.
Glaucoma: pressure-lowering eye drops, laser therapy, surgery.
AMD: intravitreal anti-VEGF injections, AREDS vitamins depending on the form.
Diabetic retinopathy: anti-VEGF, laser coagulation, optimising metabolic control.
Stroke, TIA, giant cell arteritis: immediate internal-medicine/neurological emergency treatment.
Migraine: specific acute and preventive therapy.
Diabetes and the eyes
Diabetes is one of the most important causes of visual disturbances. With strongly altered blood sugar values, the curvature of the lens can change temporarily – vision becomes blurred. The visual disturbance usually disappears after stabilisation. Important: diabetic retinopathy progresses unnoticed for a long time – this is why regular ophthalmic check-ups from the diabetes diagnosis onwards are compulsory (at least once a year).
Migraine with aura
With migraine, visual disturbances are the most common aura symptom: jagged lines (fortification spectra), scintillating scotomas, blind spots in the central field of vision – usually perceived in both eyes, lasting 5–60 minutes, followed by the typical pulsating headache. Important: an aura occurring for the first time, a long-lasting aura or an aura with additional neurological symptoms should be assessed neurologically – to distinguish it from a TIA or stroke.
Sudden loss of vision, double vision, flashes of light with a shower of soot-like floaters or acute eye pain? Call emergency number 112 immediately (in the US: 911)!
