Article Highlights

• Retinal pathology remains the most common cause of flashers and floaters, and patients should undergo prompt retinal evaluation to rule out vitreous or retinal detachment.
• Bilateral, simultaneous visual symptoms are a key clue to a neurogenic rather than retinal etiology, as retinal detachments are typically monocular.
• Migraine aura commonly presents as a scintillating scotoma with a gradual “march and buildup” of shimmering visual phenomena lasting about 20 minutes, often followed by headache.
• Occipital lobe seizures can also cause positive visual symptoms, including brief episodes of flashing or colored lights, but are not typically followed by headache.
• Persistence of visual phenomena with the eyes closed suggests a cortical source and should prompt neurological consideration when retinal examination is normal.

 

Patients who report seeing flashers or floaters often prompt urgent ophthalmologic evaluation — and for good reason. These symptoms are commonly associated with retinal issues, such as vitreous or retinal detachment.

But according to a new whiteboard video featuring Dr. Andy Lee, chair of the Blanton Eye Institute at Houston Methodist Hospital, not all such complaints stem from the eye itself.

"Floaters are usually just condensations in the vitreous," Dr. Lee explained. "They can look like spiderwebs or little specks that move across the visual field. If the vitreous pulls too hard on the retina, it can lead to a retinal detachment — that's why these patients need a retina exam."

However, when no retinal pathology is found, clinicians should consider neurological causes. One key clue is laterality.

"Retinal detachments are usually monocular," Dr. Lee said. "If the symptoms are bilateral and simultaneous, that's a red flag that we might be dealing with something in the brain."

For younger patients, the most common neurogenic cause is migraine aura. These visual disturbances often begin as jagged, shimmering lines that gradually expand across the visual field — a phenomenon Lee described as "march and buildup." Patients typically report seeing flashing lights or kaleidoscopic colors lasting about 20 minutes, followed by a throbbing headache.

"We call that a scintillating scotoma," Dr. Lee said. "It's a classic feature of migraine aura. The key is that it's positive — the patient is seeing something — and it doesn't go away when they close their eyes. That's how we know it's not coming from the eye."

Another potential cause is occipital lobe seizure, which can produce brief episodes of flashing, colored lights, often described as "tiny balls of color." Unlike migraine, these episodes are short, not followed by a headache, and can sometimes be misdiagnosed.

Dr. Lee recommends a simple test: have the patient close their eyes. "If the floater or flasher is still there, it's probably coming from the brain," he said.

While flashers and floaters are most often linked to benign posterior segment changes, Dr. Lee emphasized the importance of a thorough history and neurologic assessment when the retina appears normal.

"Retina problems are still the most common cause," he said.

Click on the image above to watch the short whiteboard video.