Perceiving flickering lights, flashes, or shimmering streaks is a visual phenomenon known as photopsia. These perceived lights can take various forms, such as quick bright flashes, shimmering zigzags, or a sensation of light without a clear shape. While often temporary and harmless, photopsia can sometimes indicate an underlying health issue that warrants further investigation. Understanding the potential origins of these visual disturbances helps individuals recognize when to seek medical advice.
Common, Harmless Reasons
Many instances of flickering lights are benign, occurring due to temporary physiological responses within the eye or body. Eye strain from prolonged focus on screens or reading can sometimes lead to transient visual disturbances, including perceived flashes of light. Similarly, physical fatigue can affect visual processing, causing fleeting perceptions of light.
Gently rubbing the eyes can also stimulate the retina and optic nerve, resulting in brief flashes or streaks of light that quickly disappear. Sudden changes in ambient light, such as moving from a dark room into bright sunlight, can produce afterimages or temporary visual phenomena as the eyes adjust.
Eye-Related Conditions
Flickering lights can also signal more specific conditions directly affecting the eye’s structure and function. Posterior vitreous detachment (PVD) is a common age-related event where the vitreous gel separates from the retina. This separation can cause the vitreous to pull on the retina, stimulating light-sensitive cells and resulting in flashes of light, often described as lightning streaks or quick bright spots. While PVD is a normal part of aging, it can sometimes lead to more serious complications.
A retinal tear occurs when the vitreous gel pulls too strongly on the retina, creating a small break in the light-sensitive tissue at the back of the eye. These tears can cause sudden flashes of light, which may be more frequent or intense than those experienced with simple PVD. If fluid passes through a retinal tear, it can lift the retina from its underlying support, leading to a retinal detachment. This condition often manifests as a sudden increase in flashes, new floaters, or a dark shadow or “curtain” obscuring part of the vision. Early detection and treatment are important for preserving vision.
In advanced stages, conditions like cataracts, which cloud the eye’s natural lens, or glaucoma, which damages the optic nerve, can also affect light perception. While not the primary symptom, significant changes in light entry or nerve function due to these conditions might lead to altered light sensations, including a perception of flickering or shimmering. These visual changes indicate a progression of the underlying eye disease.
Body-Wide and Brain-Related Causes
Beyond the eye itself, certain systemic and neurological conditions can also trigger flickering lights. Migraine with aura is a well-known example, where visual disturbances precede or accompany a headache. The aura often involves shimmering, zigzagging lines that gradually expand across the visual field, sometimes described as a “fortification spectrum” due to their resemblance to castle battlements. These visual phenomena result from abnormal electrical activity spreading across the brain’s visual cortex.
Transient ischemic attacks (TIAs), often called “mini-strokes,” occur when blood flow to a part of the brain is temporarily interrupted. Depending on the affected brain region, TIAs can cause various neurological symptoms, including sudden, temporary visual disturbances like flickering lights, dimming vision, or partial vision loss. These symptoms are typically abrupt in onset and resolve within minutes to an hour.
Low blood pressure, particularly orthostatic hypotension, which occurs when standing up quickly, can momentarily reduce blood flow to the brain and eyes. This temporary reduction can lead to a sensation of “seeing stars” or flickering lights as the visual system is briefly deprived of adequate oxygen and nutrients. Certain medications, such as those used to treat heart conditions or migraines, can also have visual side effects, including flashes or shimmering lights.
When to Consult a Doctor
While many instances of flickering lights are benign, certain symptoms warrant immediate medical attention. A sudden onset of new or significantly increased flickering lights, especially if accompanied by a sudden increase in new floaters (small specks or cobweb-like images drifting in the vision), should prompt an urgent eye examination. These combined symptoms can indicate a retinal tear or detachment, which requires prompt treatment to prevent permanent vision loss.
Other concerning signs include a sudden “curtain” or “shadow” appearing across the vision, which strongly suggests a retinal detachment. Additionally, flickering lights accompanied by symptoms not limited to the eye, such as a severe headache, weakness or numbness on one side of the body, difficulty speaking, or any sudden vision loss, require immediate emergency medical evaluation. These broader symptoms could point to neurological issues like a migraine with aura or a TIA, necessitating a comprehensive medical assessment.