Fainting, also known as syncope, is a brief loss of consciousness caused by a temporary drop in blood flow to the brain. It can happen when someone is standing up for a long time, is dehydrated, has low blood pressure, or is experiencing strong emotions. Many people report visual disturbances right before fainting. Understanding what people see before they faint can help identify warning signs so that falling-related injuries can be avoided.
Common Visual Disturbances Before Fainting
Here are some of the most common visual experiences people report prior to losing consciousness from fainting:
Tunnel Vision
Tunnel vision is one of the classic warning signs that fainting is about to occur. It refers to a substantial narrowing of the visual field, creating the sensation of looking through a tunnel. The peripheral vision starts to fade, so a person only sees what is directly in front of them. Tunnel vision results from reduced blood flow to the retina and brain. As the body’s blood pressure drops, tunnel vision usually occurs in the seconds right before fainting.
Spots or Stars
Many people notice small, flashing spots or star-like bursts of light as they start to feel faint. These visual disturbances are referred to as “floaters.” Floaters represent tiny particles drifting across the field of vision and can look like small dots, circles, clouds, or cobwebs. They occur when the vitreous gel inside the eye starts to shrink or clump together. As ocular blood flow decreases with the blood pressure drop preceding a faint, it is believed that floaters become more noticeable right beforehand.
Blurred Vision
Blurry or double vision is also commonly reported before fainting. As oxygen delivery to the retinal cells in the eye is impaired, visual processing and acuity declines. This leads to difficulty focusing and blurred vision. Things may appear fuzzy or duplicate images may be seen overlaying one another. Some people describe this as a “graying out” of their sight right before they lose consciousness.
Blacking Out
Fully blacking out visually is the last thing most people experience immediately prior to the complete loss of consciousness that defines fainting. As the brain becomes deprived of oxygen, visual information cannot be properly processed or perceived. People describe this as a rapid fading to black or feeling like a curtain is dropping over their field of vision. If blacking out occurs, the person usually will quickly progress into the faint itself.
Temporary Blindness
Some people report a brief spell of total blindness in the seconds leading up to fainting. This indicates severely impaired ocular blood flow that temporarily cuts off visual processing. There is no light or visual perception whatsoever. Once blood flow is restored after passing out and regaining consciousness, vision returns to normal. Temporary loss of sight represents an advanced warning sign of imminent syncope.
Visual Hallucinations
Less commonly, people may experience visual hallucinations prior to losing consciousness. The types of hallucinations vary widely. Some people see colors, patterns, or distorted shapes. Others report more complex hallucinations involving animals, people, or bizarre scenes. These are thought to result from the brain’s visual cortex essentially shutting down and creating random firing of neurons. Hallucinations likely indicate dangerously low blood flow to the occipital lobe where the visual cortex resides.
Underlying Causes
There are several underlying medical conditions that can lead to fainting and associated visual disturbances:
Orthostatic Hypotension
A precipitous drop in blood pressure upon standing, called orthostatic hypotension, is a major cause of fainting. When the cardiovascular system cannot properly regulate blood pressure in response to postural change, blood flow to the brain plummets. This elicits pre-fainting visual symptoms as the eyes and brain become oxygen depleted. Orthostatic hypotension can result from dehydration, medications, autonomic disorders, and certain cardiac conditions.
Vasovagal Syncope
The vasovagal reflex causes the heart rate and vascular resistance to decrease in response to triggers like fear, pain, dehydration, or prolonged standing. Vasovagal syncope produces classic prodromal symptoms like tunnel vision due to global reductions in perfusion. It is the most common underlying cause of situational fainting.
Cardiac Syncope
Cardiac syncope is fainting induced by cardiovascular disease. Reduced cardiac output or heart arrhythmias can diminish blood flow until loss of consciousness occurs. Because the visual system is so sensitive to hypoperfusion, ocular manifestations often precede cardiac syncope. Structural heart disease should be investigated in those with syncope and visual complaints.
Seizures
Epileptic seizures can sometimes mimic fainting episodes. Seizures may produce visual hallucinations, illusions, or blindness. Convulsive seizures also lead to collapse that can resemble a faint. Post-event confusion tends to last longer with seizures versus vasovagal or cardiac causes. Differentiating epilepsy from other sources of transient loss of consciousness is key.
Psychogenic Blackouts
Psychogenic non-epileptic seizures (PNES) sometimes involve momentary loss of vision and passing out. However, there is no alteration in brain activity or drop in vital signs as seen with vasovagal, cardiac, or epileptic causes. PNES blackouts are of psychiatric origin. Careful history and neurologic workup is required to distinguish PNES from true syncope.
Risk Factors
Certain people are at increased risk of experiencing visual disturbances with fainting:
Elderly
Advanced age is associated with higher rates of orthostatic hypotension and cardiac issues that can precipitate fainting. Older adults are also more prone to medication side effects that alter blood pressure. Warning symptoms like tunnel vision are important to identify before older individuals pass out and suffer injury.
Dehydration
Fluid loss is a classic precipitant for vasovagal syncope. Dehydration reduces blood volume, lowering blood pressure. Pre-faint visual changes associated with orthostasis frequently occur in those who are volume depleted. Adequate hydration is key for avoiding this.
Blood Pressure Disorders
Conditions like hypertension, dysautonomias, or carotid stenosis predispose to blood pressure drops that can lead to transient loss of consciousness. Monitoring for visual disturbances may identify patients with blood pressure disorders who are at imminent risk of full syncope.
Heart Disease
Structural heart abnormalities and arrhythmias like atrial fibrillation are linked to higher rates of cardiac syncope. Visual symptoms that precede fainting should prompt cardiology workup in those at risk for underlying heart issues. This subset needs careful management to reduce future syncopal episodes.
Seizure Disorders
Visual phenomena are commonly associated with epileptic seizures, occurring before, during, or after a seizure. Those with known seizure disorders need to differentiate pre-faint visual changes from epileptic auras to guide appropriate management when warning symptoms arise.
Warning Signs
Recognizing the early visual changes associated with near fainting allows the person to take preventive action. Here are some tips for identifying warning signs:
– Pay attention for the initial disturbance, such as tunnel vision or blurry sight, which indicates fainting may be imminent.
– Take note if visual changes are provoked by known triggers like standing too long, exposure to heat, fear, or pain. These situational factors increase risk.
– Be aware if floaters/flashes seem more pronounced than normal, as this may signify impaired ocular perfusion.
– Seek medical evaluation after multiple episodes of pre-faint visual changes to diagnose any underlying disorder.
– Be vigilant for other typical prodromal symptoms that may accompany visual disturbances, like lightheadedness, sweating, nausea, or muffled hearing.
– Consult a doctor if warning symptoms are new or increasing in frequency/severity for you.
Emergency Response
Visual disturbances signaling impending syncope require quick action to prevent traumatic falls and injury. Recommended emergency responses include:
– Sit or lie down immediately at the first sign of vision changes before losing consciousness.
– If you cannot sit, squat low to the ground and brace yourself against a wall. This helps maintain blood flow to the brain.
– Have someone assist you to the ground if pre-faint vision changes occur but you cannot safely get down yourself.
– Loosen any constrictive clothing and drink water if available.
– If you pass out, check for injury once awake. Seek medical care for any head trauma or if symptoms persist.
– For repeat fainting episodes, get evaluated by your doctor to uncover any underlying medical conditions that require treatment.
Prevention Strategies
Many cases of pre-faint visual loss can be avoided by taking some proactive precautions:
– Maintain adequate hydration and salt intake, especially with physical exertion or hot weather.
– Move slowly from lying to standing and avoid sudden postural changes.
– Engage in leg muscle contraction exercises to boost venous blood return.
– Avoid triggers like enclosed hot spaces, emotional distress, or medical procedures.
– Treat identified medical causes like heart disorders, epilepsy, or hypertension.
– Adjust prescriptions with your doctor if medications are causing blood pressure drops.
– Consume caffeine as it can help constrict blood vessels and improve orthostatic tolerance.
– Use compression garments to reduce venous pooling in the lower extremities.
Conclusion
Transient visual disturbances are common before fainting and syncope. Being aware of the typical visual symptoms like tunnel vision, blurring, and blacking out allows you to recognize when fainting is imminent and take appropriate action. If prodromal visual changes occur repeatedly, seek medical assessment to determine any underlying cause that requires treatment. With prompt response to pre-fainting warning signs and proper preventive care, major injury can often be avoided.