Seeing sudden flashes or streaks of light, often described as “strobe lights” or “lightning,” is a visual phenomenon known as photopsia. This indicates activity within the eye or brain, creating the perception of light where none exists. While occasional, fleeting flashes might be insignificant, persistent or new-onset photopsia warrants professional attention. It can signal various underlying conditions, some benign, others requiring prompt evaluation to preserve vision.
Flashes from Within the Eye
Many instances of flashes originate from changes within the eye, particularly involving the vitreous gel and the retina. The vitreous is a clear, jelly-like substance that fills the main cavity of the eye, adhering to the retina at the back. As individuals age, this gel naturally changes, becoming more liquid and shrinking, a process known as posterior vitreous detachment (PVD).
During PVD, the shrinking vitreous gel may pull on the light-sensitive retina. This mechanical stimulation of the retinal cells generates electrical impulses that the brain interprets as flashes of light. These flashes are commonly seen as brief streaks, often in the peripheral vision, and can be more noticeable in dim lighting.
While PVD is a natural aging process and harmless, the pulling action on the retina can sometimes create a retinal tear. If a tear develops, fluid from the vitreous cavity can pass through it and accumulate behind the retina, causing it to lift away from its underlying supportive tissue. This more severe condition is known as retinal detachment.
Retinal detachment is a medical emergency that can lead to permanent vision loss if not addressed quickly. Flashes associated with a retinal tear or detachment often occur suddenly and may be accompanied by a sudden increase in floaters, which appear as specks, threads, or cobwebs drifting in the vision. Other concerning signs include a shadow or “curtain” moving across the field of vision or a noticeable reduction in vision.
Flashes Beyond the Eye
Flashes of light can also stem from sources outside the eye, often related to neurological activity. A common non-ocular cause is migraine, which can manifest as visual disturbances known as auras. Ocular migraine, also called retinal migraine, specifically involves visual symptoms in only one eye, such as temporary blind spots, shimmering, or zigzag patterns.
Migraine with aura, in contrast, affects both eyes and presents with visual disturbances before or during a headache. These auras can include zigzag lines, flashing lights, shimmering spots, or blind spots that often expand over 10 to 30 minutes. The visual symptoms of both ocular migraine and migraine with aura are temporary, resolving within an hour.
Beyond migraines, other conditions can also cause perceived flashes. Neurological issues, such as those affecting the occipital lobe of the brain or even seizures, may produce these visual phenomena. Systemic factors, including sudden changes in blood pressure, like standing up too quickly, or certain medications, can induce brief visual disturbances. Inflammation of the optic nerve, known as optic neuritis, is another condition that can lead to flickering lights in the field of vision.
Recognizing Urgent Symptoms
While some flashes of light are benign, certain associated symptoms indicate a need for immediate medical evaluation. A sudden onset of new flashes, especially if they increase significantly in number or intensity, is a concern. Similarly, a sudden increase in the number of floaters, or the appearance of new, larger floaters, requires prompt attention.
An urgent symptom is the presence of a dark shadow or “curtain” moving across any part of the field of vision, which can indicate a retinal issue like detachment. Any associated reduction in vision, including blurred vision or loss of peripheral sight, also requires immediate medical consultation.
If flashes are accompanied by other symptoms like eye pain, numbness, or difficulties with speech, seeking immediate medical help is important. These combined symptoms could suggest broader systemic issues that require diagnosis and intervention. Ignoring such warning signs could lead to irreversible vision loss.
Medical Evaluation and Management
When experiencing flashes of light, a medical evaluation begins with a detailed discussion of symptoms and medical history. The main diagnostic procedure is a comprehensive dilated eye exam. During this exam, eye drops widen the pupil, allowing the eye care professional a clear view of the retina at the back of the eye.
An ophthalmoscope, an instrument with a bright light and special lenses, is then used to examine the retina for any tears, holes, or signs of detachment. In some cases, additional imaging tests such as an ultrasound or optical coherence tomography (OCT) may be performed to gain more detailed views of the retinal structures.
The management approach for photopsia depends on the underlying cause. If a posterior vitreous detachment is diagnosed without any retinal tears, observation is often sufficient, as the flashes and floaters become less noticeable over time. However, if a retinal tear is found, laser treatment or cryopexy (freezing) may be performed to seal the tear and prevent a full retinal detachment.
For a confirmed retinal detachment, surgical intervention is necessary to reattach the retina and preserve vision. Procedures like vitrectomy, scleral buckling, or pneumatic retinopexy are common. For flashes caused by migraines, management involves avoiding known triggers, using pain relievers, or specific migraine medications. A professional diagnosis is important to determine the appropriate course of action.