Flashes of light seen when your eyes are closed can be a surprising and sometimes unsettling experience. This visual phenomenon, known as photopsia, often appears as brief streaks, sparks, or shimmering patterns. While frequently harmless, understanding the reasons behind these flashes helps clarify when they are a normal part of visual perception and when they might signal a more significant concern.
How the Eye Perceives Flashes
The eye can perceive light sensations even without external light sources, a phenomenon known as phosphenes. These visual experiences arise when the retina’s photoreceptors, the light-sensitive cells at the back of the eye, or the optic nerve are stimulated by something other than light. Mechanical pressure, electrical signals, or random firing of cells within the visual system can trigger these sensations, tricking the brain into interpreting them as light.
Common Benign Flashes
Several everyday situations can cause these harmless phosphenes. Rubbing your eyes often produces a swirling pattern of light and color as the mechanical pressure stimulates the retina. Similarly, applying gentle pressure to the eyelids can induce temporary flashes.
Phosphenes can also occur with sudden changes in blood pressure, such as standing up too quickly, which might cause you to “see stars.” Sneezing or a heavy cough can also generate brief flashes due to transient pressure changes within the head and eyes. Even in a very dark room, the eyes can generate faint, swirling patterns of light as they adapt to the low light conditions. These instances are generally normal.
Medical Conditions Causing Flashes
While many flashes are benign, some medical conditions can also cause them, indicating a need for professional evaluation. One common age-related change is Posterior Vitreous Detachment (PVD), where the vitreous gel filling the eye naturally shrinks and pulls away from the retina. This pulling can stimulate the retina, resulting in flashes often described as lightning streaks or camera flashes, particularly noticeable in peripheral vision. PVD itself is usually harmless, but the vitreous pulling can sometimes lead to more serious issues.
A more serious condition is retinal detachment, where the retina pulls away from the underlying tissue that supplies it with oxygen and nutrients. This can cause sudden, persistent flashes, often accompanied by a significant increase in floaters (specks or cobweb-like shapes in your vision). A “curtain” or “veil” obscuring part of the vision is another serious sign. Retinal detachment requires urgent medical attention to prevent permanent vision loss.
Flashes can also be a symptom of ocular migraine, sometimes called migraine aura without headache. These visual disturbances typically affect both eyes and can include zigzag lines, shimmering lights, blind spots, or flashes. Ocular migraines are thought to be caused by temporary changes in blood flow to the visual cortex of the brain. While they can be unsettling, they are generally not harmful to the eye itself.
When to Seek Medical Attention
Seek prompt medical attention from an eye care professional if you experience new or changing flashes. A sudden onset of new flashes, especially if they are frequent or intense, warrants evaluation. Any flashes accompanied by a sudden increase in floaters (small specks or cobweb-like shapes) should also be immediately checked.
A particularly concerning symptom is the appearance of a “curtain” or “veil” obscuring any part of your vision, or any associated loss of peripheral or central vision. Flashes occurring after a head trauma also require immediate medical assessment. These symptoms could indicate a serious underlying condition, such as a retinal tear or detachment, which needs timely intervention to protect vision.
Medical Evaluation and Potential Treatment
When you see an eye doctor for flashes, a comprehensive eye examination will be performed. This typically includes a dilated eye exam, where eye drops are used to widen your pupils, allowing the doctor a clear view of the retina and vitreous gel at the back of your eye. In some cases, additional imaging tests may be used to further assess the eye’s internal structures.
Based on the findings, the doctor will determine the cause of the flashes. For Posterior Vitreous Detachment (PVD) without complications, observation is often the approach, as symptoms typically subside over time. If a retinal tear is identified, laser treatment or cryotherapy may be performed to seal the tear and prevent it from progressing to a retinal detachment.
Retinal detachment usually requires surgical intervention to reattach the retina. For ocular migraines, management focuses on identifying and avoiding triggers, such as stress or certain foods. Pain relievers or, in some cases, preventative medications may be prescribed to manage symptoms.