When you notice flashing lights in your peripheral vision, the area outside your direct line of sight, it can be unsettling. This sensation, described as streaks, shimmering, or brief flickers, occurs in your side vision without an external light source. Peripheral vision allows you to detect objects and movement in your surroundings.
Understanding Peripheral Flashes
The sensation of flashing lights often originates from internal eye processes, specifically involving the vitreous humor and the retina. The vitreous humor is a clear, gel-like substance that fills the space between the lens and the retina. It helps maintain the eye’s spherical shape and provides structural support to the retina.
The retina is a thin, light-sensitive tissue at the back of the eyeball. It converts light into electrical signals, sent to the brain to create images. As people age, the vitreous humor can liquefy and shrink. This natural process can cause the vitreous to pull on the retina, which the brain interprets as flashes because the retina’s light-sensing cells are mechanically stimulated.
Common Explanations for Flashes
Many peripheral flashes are due to common conditions. One frequent cause is Posterior Vitreous Detachment (PVD). This occurs when the vitreous gel liquefies with age and naturally separates from the retina. The pulling of the vitreous on the retina during this separation can cause flashes, often described as streaks or lightning, particularly noticeable in dimmer environments. While PVD is a natural aging process, it can sometimes precede more serious issues.
Another explanation for visual disturbances, including flashes, is an ocular migraine or migraine aura. These neurological events cause temporary visual symptoms in both eyes, such as shimmering lights, zigzag lines, or blind spots. Unlike flashes caused by vitreous changes, migraine auras originate in the brain and last a short duration, and may or may not be followed by a headache.
Serious Conditions Requiring Attention
While many flashes are benign, some signal serious, sight-threatening conditions requiring prompt medical evaluation. A retinal tear can occur if the vitreous gel pulls forcefully enough to break the retina. Flashes might intensify or be accompanied by a sudden increase in floaters (dark spots or “cobwebs”). An untreated retinal tear can allow fluid to seep behind the retina, leading to a more severe condition.
This more severe condition is retinal detachment, where the retina peels away from its underlying tissue. Flashes can be a symptom, often with a sudden increase in floaters. Other signs include a “curtain” or “shadow” obscuring part of your vision, or general dimming. Retinal detachment requires immediate attention because the detached retina loses its blood supply, and delayed treatment can result in permanent vision loss.
Knowing When to Seek Care
Seek medical attention if you experience new or changing flashes. Urgent signs requiring immediate evaluation include a sudden onset of flashes, a significant increase in their number or intensity, or flashes accompanied by a dark “curtain” or shadow spreading across your vision. Vision loss, blurred vision, or eye pain with flashes also indicate immediate care. These symptoms could point to a retinal tear or detachment, requiring prompt intervention.
Even if flashes are new but lack urgent signs, seek an eye examination. An ophthalmologist is the appropriate professional to consult for these symptoms. They can conduct a thorough dilated eye exam to determine the cause and rule out serious issues, ensuring timely treatment to preserve vision.