Brief flashes of light, especially in side vision or when moving the head, are known as photopsia. This visual sensation resembles streaks of lightning or camera flashes but occurs without any external light source. While often a sign of common, age-related changes inside the eye, photopsia can also signal serious underlying conditions. Understanding the cause is important for protecting long-term vision health.
Understanding the Sensation of Photopsia
Photopsia is the medical term for the perception of light when no actual light is present in the environment. This phenomenon arises because the retina, the light-sensitive tissue at the back of the eye, is stimulated mechanically rather than by light energy. The retina contains photoreceptor cells that interpret any form of stimulation as light and send a corresponding electrical signal to the brain.
The eye’s interior is filled with a clear, gel-like substance called the vitreous humor, which is firmly attached to the retina. As a person ages, this vitreous gel naturally begins to liquefy and shrink, causing it to pull away from the back wall of the eye. This traction, or pulling, on the sensitive retinal tissue generates the electrical impulse that the brain registers as a flash of light. Flashes resulting from this pulling action are typically seen as quick, arc-like streaks in the peripheral vision.
Common Ocular Causes of Peripheral Flashes
The most frequent cause of new flashes and floaters is Posterior Vitreous Detachment (PVD). PVD occurs when the shrinking vitreous gel separates from the retina, a process that happens to most people, with about 75% experiencing it by age 65. The flashes are most noticeable during the period of separation when the vitreous is actively tugging on the retina, and they often become less frequent as the separation completes.
While PVD is usually a benign, natural aging process, the traction exerted by the separating vitreous can be strong enough to cause a breach in the retinal tissue. A retinal tear is a small rip in the retina that allows fluid to pass underneath and potentially lift the retina away from the back of the eye. This lifting away is known as a retinal detachment, a serious condition that can lead to permanent vision loss if not repaired quickly.
Retinal tears occur in approximately 10% to 15% of symptomatic PVD cases, making a comprehensive eye exam necessary following the onset of flashes. The flashes associated with tears and detachments often feel more intense or persistent than those from simple PVD.
Migraine with Aura
Another distinct cause of flashes is a migraine with aura. These flashes are not caused by retinal traction but by a wave of electrical activity across the brain’s visual cortex. Migraine-related flashes usually appear as geometric, shimmering zigzag lines that affect both eyes simultaneously and move across the central vision, typically lasting between five minutes and one hour.
Recognizing Signs of an Eye Emergency
The appearance of flashes and floaters necessitates an immediate evaluation to distinguish between a routine PVD and a sight-threatening complication.
- A sudden, dramatic increase in the number or brightness of the flashes, often described as a burst of light or lightning that does not subside.
- The simultaneous appearance of a “shower” or “swarm” of new floaters, such as black spots, clouds, or cobwebs.
- The development of a shadow, curtain, or veil that blocks a portion of the side or central vision.
This visual field defect suggests the retina has fully detached and requires emergency medical attention to prevent irreversible damage.
Diagnosis and Management of Flashes
A diagnosis for photopsia begins with a comprehensive eye examination performed by an eye care professional. This examination includes dilating the pupils with medicated drops to allow the doctor to gain a clear, wide-angle view of the entire retina and the vitreous humor. The doctor will use specialized tools, such as an ophthalmoscope, to look for any signs of tugging, tears, or detachment.
If the diagnosis is uncomplicated Posterior Vitreous Detachment, the management typically involves observation and patient education, as the condition is not vision-threatening and the symptoms usually lessen over weeks or months. The patient is instructed to monitor for any worsening symptoms that could signal a complication.
When a retinal tear is found, prompt treatment is usually recommended to prevent progression to detachment. Treatment for a tear often involves a quick, in-office procedure using a laser to seal the edges of the tear to the back of the eye, a process called laser photocoagulation. If a full retinal detachment has occurred, surgical intervention is necessary to reattach the retina. Procedures like a vitrectomy or scleral buckle are performed to secure the retina back into its proper position.