Seeing flashes of light in the corner of one’s eye can be unsettling. This common visual phenomenon, while often benign, warrants understanding due to its varied origins. These visual disturbances typically arise from processes within the eye itself, not external light sources.
Understanding the Phenomenon
The sensation of seeing flashes of light, medically termed photopsias or phosphenes, arises from the retina or visual pathways being stimulated by something other than actual light. The retina, a light-sensitive tissue at the back of the eye, converts light into electrical signals. When mechanically stimulated, it interprets this as light, leading to flashes. These can manifest as brief streaks, bright spots, or shimmering patterns.
The vitreous, a gel-like substance filling the eyeball, plays a significant role in many instances of perceived flashes. As people age, the vitreous can liquefy and shrink. This process can cause the vitreous to pull on the retina, creating tension that the brain interprets as flashes of light.
Common Explanations
Many light flashes are temporary and not indicative of serious eye problems. Simple actions like rubbing the eyes, sneezing, coughing forcefully, or experiencing low blood pressure can mechanically stimulate the retina, causing brief flashes or “seeing stars.” These resolve quickly once the stimulation stops.
Another common cause is the visual aura associated with migraines, sometimes called ocular or visual migraines. These disturbances appear as zigzag lines, shimmering lights, bright spots, or blind spots, with or without a headache. Migraine auras usually affect both eyes, last 5 to 60 minutes, and originate from electrical activity in the brain’s visual cortex, unlike retinal flashes.
A frequent age-related cause is posterior vitreous detachment (PVD), where the vitreous gel naturally separates from the retina. This normal aging process usually occurs without pain or vision loss. During PVD, the shrinking vitreous may tug on the retina, causing flashes that often appear as brief streaks of light in the peripheral vision. Flashes from an uncomplicated PVD typically subside as the separation completes.
Potential Serious Causes
While many eye flashes are benign, some signal serious underlying conditions requiring prompt medical attention. The primary concern relates to issues with the retina. When the vitreous gel pulls too strongly on the retina, it can lead to a retinal tear. Retinal tears are breaks in the retina that can allow fluid to pass through, potentially leading to a more severe condition. Flashes associated with a retinal tear are often described as repeated flashes, like lightning streaks or shooting stars, and may be accompanied by a sudden increase in floaters.
An untreated retinal tear can progress to a retinal detachment. This is an emergency where the retina pulls away from its normal position, separating from its blood supply. Symptoms include a sudden appearance of flashes and floaters, blurred vision, and often a curtain-like shadow or loss of peripheral vision. This condition is painless but can lead to permanent vision loss if not addressed quickly.
Less common systemic causes include conditions affecting brain blood flow, like vertebrobasilar insufficiency, or optic nerve inflammation (optic neuritis). Rare neurological conditions, such as occipital epilepsy, can also cause flashes, though these are typically shorter than migraine auras.
When to Seek Medical Care
It is important to recognize when eye flashes indicate a serious problem requiring professional medical evaluation. Any sudden onset of new flashes, especially with a significant increase in number or intensity, warrants immediate attention from an eye care professional. A prompt visit to an optometrist or ophthalmologist is recommended to rule out serious conditions.
Key “red flag” symptoms include the sudden appearance of new floaters, particularly a burst of many small specks or a large, cobweb-like floater. The presence of a shadow or “curtain” moving across any part of the vision, or any sudden loss of vision, also demand immediate evaluation.
Early detection and treatment of retinal tears or detachments are crucial to preserving vision, as delaying care can lead to permanent sight loss. During an eye exam, the doctor will likely dilate the pupils to view the retina and check for tears, detachments, or other issues.