Experiencing a temporary loss or change in vision, such as blurring, dimming, or a brief blackout, during or immediately after a forceful cough can be unsettling. This phenomenon, while often transient and harmless, can be concerning. Understanding the physiological processes involved and the potential underlying factors can help explain this experience.
Understanding the Mechanism
A strong cough initiates a series of physiological responses similar to the Valsalva maneuver, a forced exhalation against a closed airway. This action rapidly increases pressure within the chest and abdomen, known as intrathoracic and intra-abdominal pressure. This surge in pressure can be significant, potentially reaching up to 300 mmHg for several seconds during a forceful cough.
The increased pressure in the chest temporarily reduces the amount of blood returning to the heart from the body, leading to a temporary drop in heart output. This results in a transient decrease in systemic blood pressure, which in turn reduces blood flow to the brain and eyes, particularly the retina and visual cortex. A temporary reduction in cerebral blood flow velocity can be as high as 52%. This momentary decrease in blood supply causes the visual disturbance experienced during or immediately after a strong cough.
Potential Underlying Causes
While the temporary vision changes from coughing are frequently benign, certain conditions or factors can make an individual more susceptible. One such condition is benign cough syncope, a temporary loss of consciousness or near-fainting episode triggered by coughing. This more pronounced response is directly related to the mechanisms of reduced blood flow to the brain.
Orthostatic hypotension, a condition where blood pressure drops significantly upon standing, can exacerbate the effects of coughing on vision. If blood pressure is already low, the additional transient drop caused by coughing can more easily lead to visual symptoms or fainting. Dehydration or exhaustion can also contribute by lowering overall blood volume and blood pressure, making the body more sensitive to the pressure changes induced by coughing.
Cardiovascular conditions, such as certain heart arrhythmias, heart valve issues, or narrowing of the carotid arteries, may also contribute to vision changes during coughing. Congestive heart failure, for instance, can lead to fluid buildup in the lungs, triggering a cough and potentially impacting vision due to reduced blood flow to the eyes. Neurological conditions, though less common, can sometimes be linked, especially those affecting brain pressure or blood vessels. These might include certain types of headaches, or rarely, structural brain issues like a Chiari malformation.
Certain medications can also increase susceptibility to vision changes or lightheadedness when coughing. Blood pressure-lowering drugs, such as ACE inhibitors like lisinopril, or diuretics, can lower overall blood pressure and worsen the temporary drop caused by coughing.
When to Seek Medical Attention
While temporary vision changes with coughing are often harmless, certain signs warrant prompt medical evaluation to rule out serious underlying conditions. Seek immediate medical attention if the vision loss is prolonged, lasting more than a few seconds, or if it occurs without a strong cough.
Additional concerning symptoms that warrant medical consultation include severe headache, weakness or numbness on one side of the body, confusion, speech changes, or chest pain. If episodes of vision change become more frequent or severe, or if they cause significant distress, consult a healthcare professional.
A doctor will likely conduct a thorough physical examination, review your medical history, and may order specific tests. These tests could include blood pressure checks, an electrocardiogram (ECG) to assess heart rhythm, or a neurological exam. Imaging studies, such as magnetic resonance angiography or cerebrovascular ultrasound, may be considered to evaluate blood vessel patency. Professional evaluation is important to identify any underlying causes and recommend appropriate management or treatment.