Seeing flashes of light or patterns when your eyes are closed is known as phosphenes or entoptic phenomena. These visual sensations originate within the eye or brain. While often normal and harmless, they can sometimes signal an underlying health concern. This article discusses common reasons for these flashes and when they might indicate a serious issue.
Understanding Benign Flashes
Many flashes experienced with closed eyes are normal. Pressure phosphenes, for instance, occur when mechanical pressure is applied to the eye. Rubbing your closed eyes can stimulate retinal cells, causing perceptions of light, colors, or shapes. Sudden jolts, sneezes, or strong coughs can also induce these flashes.
Benign flashes also arise from the visual system’s spontaneous activity. Retinal and visual cortex cells can fire randomly, even in darkness. This natural “visual noise” is usually filtered during normal vision but becomes noticeable without external light. These internal signals appear as subtle, shimmering patterns or static-like dots, often described as pixelated.
When Flashes Indicate a Problem
Flashes can signal more significant eye conditions, especially those affecting the retina. Posterior vitreous detachment (PVD) is a common age-related process where the vitreous gel separates from the retina. As it pulls away, it can tug on the retina, causing flashes like streaks or lightning bolts, often in peripheral vision. PVD frequently occurs with new or increased “floaters,” which are small specks or cobweb-like shapes drifting in your vision.
Retinal detachment is a serious condition where the retina pulls away from its supporting tissues. This can occur if the vitreous gel tears the retina. Symptoms include a sudden increase in flashes, a shower of new floaters, and a dark shadow or “curtain” in your field of vision. This medical emergency requires prompt treatment to prevent permanent vision loss.
Flashes can also be part of migraine aura, visual disturbances preceding or accompanying a migraine. These flashes may appear as zigzag patterns, shimmering lights, or blind spots, affecting both eyes. Ocular migraines, a rarer type, cause visual symptoms like blind spots or flashes in only one eye. Though alarming, these disturbances are temporary, lasting minutes to an hour.
Knowing When to Consult a Doctor
Consult an eye care professional promptly if you experience certain warning signs with flashes. Seek immediate attention for a sudden onset or significant increase in flash frequency or intensity. This is especially true if flashes accompany new or increased floaters, which can appear as numerous small specks or a large, dense cobweb.
Other concerning symptoms requiring urgent evaluation include sudden partial vision loss, like a dark shadow or “curtain” in your visual field. Flashes after an eye injury or trauma also need immediate assessment. These symptoms may indicate a retinal tear or detachment, requiring timely intervention to preserve vision. Do not self-diagnose; an eye specialist ensures proper diagnosis and management.