When your eyes go black for a few seconds, it's usually a temporary vision loss called amaurosis fugax (from poor blood flow to the retina) or orthostatic hypotension (sudden blood pressure drop), causing dizziness or fainting. It's a serious symptom, often signaling underlying issues like blood clots, plaque, heart problems, migraines, or neurological conditions, requiring prompt medical evaluation to rule out stroke or heart attack risk.
When a blood vessel in your retina tightens, it causes a vasospasm. This cuts down on blood flow, which can bring on temporary vision loss in one eye. Various conditions can lead to a vasospasm. These include a retinal migraine, atherosclerosis, and high blood pressure.
This is called orthostatic hypotension, and it occurs when blood pressure drops suddenly after you stand or change posture. Orthostatic hypotension is part of a category of temporary loss of vision called transient obscurations of vision (TOV), which only last for several seconds.
Eye Pressure Problems: Sudden changes in intraocular pressure can cause darkening of the eyes. Migraine Attacks: Migraine can cause vision problems along with headaches, which can lead to sudden blackouts. Vertigo: Vertigo attacks due to inner ear problems can cause blackouts.
The term amaurosis fugax means 'transient darkening' and it is used by doctors to describe a temporary loss of vision through one eye, which returns to normal afterwards. This is usually due to a temporary disturbance of the blood flow to the back of the eye.
Typically, black spots in vision, cobwebs, or seeing flashing lights in the eyes are caused by age-related vitreous degeneration or nearsightedness. The vitreous humor, a gel-like substance similar to egg white, located between the lens and the retina, serves as a medium for light to pass through.
Early signs of an eye stroke (retinal artery occlusion or ischemic optic neuropathy) typically involve sudden, painless vision loss or changes, most often in only one eye, including blurred vision, blind spots, floaters, or a dark shadow covering part of your sight. It often happens upon waking and is a medical emergency requiring immediate attention to potentially save sight and identify a risk for a full stroke.
Most unexplained blackouts are caused by syncope
Many people, including doctors, assume that blackouts are due to epileptic seizures, but much more commonly they are due to syncope (pronounced sin-co-pee) – a type of blackout which is caused by a problem in the regulation of blood pressure or sometimes with the heart.
While there are many and varied causes of sudden temporary vision loss, it's possible you may be at risk of a stroke. The official term for this type of symptom is called a “transient ischemic attack”, or TIA.
Is a sudden black eye without injury normal? While uncommon, a sudden black eye without injury may occur due to underlying medical conditions like bleeding disorders, sinus infections, or allergic reactions. It's important to seek medical advice if no trauma is apparent.
Transient Ischemic Attack (TIA)
Often referred to as a “mini-stroke,” a TIA is caused by a temporary lack of blood flow to the brain. This can result in sudden vision loss or blackouts. Symptoms include sudden weakness, numbness, difficulty speaking, and loss of balance.
Blurred vision or partial/complete vision loss may be signs that you are having a stroke. Sudden vision changes could also have other causes.
Flash blindness occurs when an extremely bright flash is discharged, usually at night, and again vision is temporarily lost." The United States Federal Aviation Administration defines flash blindness in Order JO 7400.2 as "generally, a temporary visual interference effect that persists after the source of the ...
Constantly low blood pressure can be dangerous if it causes signs and symptoms such as:
Heart conditions can disrupt blood flow to the eyes, leading to vision changes. Strokes and transient ischemic attacks (TIAs), often called mini-strokes, can cause sudden, temporary vision loss or blurred vision. If you experience these symptoms, seek medical help immediately.
Dizzy spells and blackouts can have a variety of causes, such as low blood pressure, an abnormal heart rhythm, an inner ear problem, or anaemia.
Other signs and symptoms may include:
Different conditions, including keratitis, trauma, hyphema, uveitis, acute glaucoma, optic neuritis, papilledema and retinal detachment, can cause sudden loss of vision.
Even without obvious symptoms, silent strokes raise the risk of future strokes and can lead to cognitive decline or vascular dementia. Key warning signs include sudden mood changes, memory issues, balance problems, and cognitive difficulties — but only MRI or CT scans can confirm a silent stroke.
Most fainting will pass quickly and won't be serious. Usually, a fainting episode will only last a few seconds, although it will make the person feel unwell and recovery may take several minutes.
Fainting is a type of blackout. The medical term is syncope. It is when you lose consciousness for a short time.
Before collapsing, you may: feel nauseous (feel sick) or vomit. have a stomach ache. suddenly feel warm or sweaty.
It usually affects part of the vision in that eye – for example the upper or lower part. In some cases, there's only a temporary blockage and vision returns quickly – this is often described as a 'mini-stroke'. People who develop sudden loss of vision should see an expert urgently.
The 5 key warning signs of a stroke, often remembered with the FAST acronym, are sudden Face drooping, Arm weakness, Speech difficulty, and the crucial Time to call 911; other signs include sudden trouble seeing, walking, dizziness, or a severe headache, requiring immediate emergency care.
“Brief vision changes in one eye can be a sign of an oncoming stroke,” says Chief of Neuro-Ophthalmology, Robert C. Sergott, MD of Wills Eye. “If temporary blurriness or reduced vision is due to an oncoming stroke, you may only have a few hours to get emergency care before a stroke occurs.”