Flashes of light in your vision are usually caused by physical tugging on the retina, the light-sensitive layer at the back of your eye. The most common reason is the gel inside your eye shrinking and pulling away from the retina as you age. This process is extremely common and typically harmless, but in a small percentage of cases, it signals something more serious like a retinal tear. Understanding the difference matters because a tear, caught early, can be fixed with a simple outpatient laser procedure before it progresses to vision-threatening retinal detachment.
Why Your Eye Produces False Light
Your eye is filled with a clear, gel-like substance called the vitreous. When you’re young, this gel is thick and firmly attached to the retina. As you age, it gradually liquefies and shrinks, pulling on the retina as it does. The retina can’t actually feel touch or pressure. It only knows how to do one thing: detect light. So when the vitreous tugs on it, your brain interprets that mechanical stimulation as a flash or streak of light, even though no actual light entered your eye.
These flashes are called photopsias. People describe them in different ways: a camera flash in the corner of your eye, a streak of lightning, or a brief sparkle. They tend to be more noticeable in darker environments and usually appear at the edges of your vision rather than dead center.
Posterior Vitreous Detachment: The Most Common Cause
The most likely explanation for new flashes of light, especially if you’re over 50, is posterior vitreous detachment (PVD). This happens when the vitreous gel separates from the retina entirely. It typically begins in your 60s or 70s and affects most people by their 80s. Men and women are equally affected.
PVD isn’t painful, and it doesn’t cause vision loss on its own. Along with flashes, you may notice new floaters: small specks, cobwebs, or squiggly lines drifting across your field of vision. Some people see a ring-shaped floater, which forms when tissue peels away from the optic nerve at the back of the eye. The flashes usually settle down over weeks to months as the vitreous finishes separating and stops pulling on the retina. The floaters often persist longer but become less noticeable as your brain learns to ignore them.
People who are nearsighted tend to develop PVD earlier because their eyes are longer, which puts more strain on the vitreous-retinal connection. Previous eye surgery or eye injuries can also speed up the process.
When Flashes Signal a Retinal Tear or Detachment
The concern with PVD isn’t the detachment itself but what it can cause. When the vitreous pulls away, it sometimes tears the retina. Among people whose PVD involves bleeding inside the eye (vitreous hemorrhage), about 35% have a retinal tear at the time of diagnosis, and roughly 9% already have a retinal detachment. Even after the initial evaluation, new tears can develop in the following months.
A retinal tear left untreated can allow fluid to seep behind the retina, peeling it away from the tissue that nourishes it. This is retinal detachment, and it’s a medical emergency that can cause permanent vision loss. The symptoms to watch for include:
- A sudden increase in floaters, especially many tiny specks appearing at once
- A shadow or curtain creeping across part of your vision from any direction
- Worsening peripheral vision that feels like your field of view is narrowing
- Blurred or reduced vision that comes on quickly
A single flash here or there over several weeks is a very different situation from a sudden shower of flashes and floaters. The sudden, dramatic onset is the pattern that warrants immediate attention.
How Migraine Flashes Look Different
Not all visual flashes come from the retina. Migraine auras originate in the brain and produce a distinctly different visual experience. Instead of brief streaks of white light at the edge of your vision, migraine auras typically create geometric patterns: zigzag lines, shimmering arcs, or expanding blind spots with flickering borders. These patterns usually build over 5 to 30 minutes and then fade, often followed by a headache (though not always).
One key distinction is which eyes are involved. Migraine with aura affects both eyes because the signal comes from the brain’s visual processing area, not from either eye individually. If you close one eye and the visual disturbance is still there, it’s almost certainly a migraine aura. Retinal flashes from PVD or a tear affect only one eye. A rarer condition called retinal migraine also affects just one eye, but the vision disruptions tend to be more severe, sometimes causing temporary partial blindness that resolves within an hour.
If you’ve had migraine auras before and the pattern is familiar, you likely know what you’re dealing with. New or unfamiliar visual symptoms that don’t match your typical aura are worth getting checked.
Less Common Causes
Several other conditions can produce flashes of light. Optic neuritis, an inflammation of the nerve connecting the eye to the brain, can cause flashes along with pain during eye movement and dimmed or washed-out vision. This condition is sometimes associated with multiple sclerosis. Reduced blood flow to the retina from a blocked blood vessel can also trigger flashes, usually accompanied by sudden, painless vision loss in one eye.
Certain medications have been linked to visual disturbances that resemble flashes. Some heart medications, antipsychotics, and chemotherapy drugs can cause a perception of widespread flickering or visual “snow.” These drug-related effects tend to involve both eyes equally and look more like television static than the distinct streaks or sparks that come from retinal traction.
What Happens During an Eye Evaluation
When you see an eye doctor for new flashes, the exam is straightforward. They’ll check your visual sharpness with a standard eye chart, test your peripheral vision by asking you to count fingers held in different positions, and shine a light back and forth between your eyes to check how your pupils respond. An abnormal pupil response can point to a problem with the optic nerve or significant retinal damage.
The most important part of the evaluation is a dilated retinal exam. Drops widen your pupils so the doctor can see the retina directly, looking for tears, detachment, or bleeding. In some cases, they’ll use an imaging scan to get cross-sectional pictures of the retina or an ultrasound if blood in the vitreous is blocking the view.
If a retinal tear is found, laser retinopexy can seal the tear in an outpatient visit, preventing fluid from getting behind the retina. This is highly effective at stopping a tear from progressing to a full detachment. If the retina has already detached, surgical repair is needed, and outcomes are better the sooner it’s addressed.
How Quickly to Get Checked
The timeline depends on the pattern. If you notice a curtain-like shadow over your vision, sudden vision loss, or a dramatic burst of new floaters alongside flashes, that warrants evaluation within hours, not days. Clinical guidelines recommend assessment within 24 hours when retinal detachment is suspected.
For a new onset of occasional flashes and floaters without the red-flag symptoms above, the standard recommendation is evaluation within 24 to 48 hours. This is considered urgent but not a drop-everything emergency.
If you’ve had mild flashes on and off for months or years and nothing has changed, a routine eye exam is reasonable. Long-standing, stable symptoms are far less likely to indicate an active problem. That said, even benign PVD carries a small risk of delayed complications in the months after onset, so an initial evaluation still has value if you’ve never had one.