Many people occasionally experience the sensation of seeing “stars” or flashes of light in their vision. These visual phenomena, medically termed photopsia, are not external light sources but rather perceptions generated within the eye or brain. Understanding the various reasons behind these flashes, some of which are benign and others indicative of serious conditions, is important for maintaining eye health.
Understanding Visual Flashes
Visual flashes manifest as sudden, brief sparks, streaks, or shimmering lights in the field of vision. These internal light sensations, known as photopsias, can appear as white or sparkly lights, zigzag lines, lightning bolts, or flickering spots. Unlike external light, these flashes originate from stimulation of the retina, the light-sensitive tissue at the back of the eye. While flashes and floaters—dark spots or squiggly lines—often occur together, they are distinct phenomena, with floaters being shadows cast by debris within the eye. Any mechanical stimulation of the retina, such as pulling or tugging, can cause it to transmit a light impulse to the brain, even in darkness.
Posterior Vitreous Detachment
Posterior Vitreous Detachment (PVD) is a common cause of eye flashes, particularly among older adults. The vitreous humor is the clear, gel-like substance that fills the eye and helps maintain its shape. As individuals age, typically after 50, the vitreous naturally undergoes changes, becoming more liquid and shrinking. This process can cause the vitreous to pull away from the retina, leading to a PVD.
When the vitreous humor detaches, it can tug on the retina, causing mechanical stimulation that the brain interprets as flashes of light. These flashes are often described as lightning streaks or camera flashes in the peripheral vision and typically last less than a second. While PVD itself is not painful or sight-threatening, it can sometimes lead to more serious conditions like a retinal tear. Most patients find that the flashes and floaters associated with PVD become less noticeable over several weeks or months as the brain adjusts.
Retinal Tears and Detachment
Retinal tears and detachments can arise from the same forces causing eye flashes, often following a Posterior Vitreous Detachment. A retinal tear is a break in the retina, which can occur if the vitreous gel pulls too strongly on it during detachment. If a tear develops, fluid from the vitreous can pass through the opening and collect behind the retina, causing it to lift away from its underlying support tissue, a condition known as retinal detachment.
Flashes associated with a retinal tear or detachment are often described as sudden, numerous, or intense, sometimes appearing as lightning streaks or stars. A key sign of retinal detachment is the appearance of a “curtain” or “veil” obscuring part of the vision. These conditions are medical emergencies because the detached retinal cells lose their blood supply, which can lead to permanent vision loss if not treated promptly. Surgical intervention, such as laser treatment or cryotherapy for tears, or more complex surgery for detachments, is often required to reattach the retina and preserve vision.
Migraines and Other Visual Disturbances
Visual flashes can also result from migraines. Ocular migraines, or migraines with aura, typically involve visual disturbances such as shimmering zigzag lines, flashing lights, or blind spots. These visual auras usually develop gradually over 5 to 20 minutes and typically resolve within an hour. While they often precede a headache, these visual symptoms can also occur without any headache, a phenomenon known as “silent migraine” or “migraine aura without headache.”
Other less common causes of temporary flashes include mechanical stimulation, such as rubbing the eyes or a blow to the head, which can cause transient “stars” due to pressure on the retina. Sudden changes in blood pressure, certain medications, or rare inflammatory conditions like optic neuritis can also induce flashes. These varied origins show that visual flashes can indicate diverse health concerns, both ocular and neurological.
When to See a Doctor
It is important to seek prompt medical attention from an eye care professional if you experience visual flashes. Immediate evaluation is necessary for symptoms such as the sudden onset of new flashes, a significant increase in their number or intensity, or the appearance of new or increased floaters. A shadow or “curtain” in your vision, or any sudden vision loss, requires immediate medical attention.
While some flashes are harmless, an individual cannot self-diagnose the underlying cause. A comprehensive dilated eye exam by an ophthalmologist is the only way to determine the source of the flashes and rule out serious conditions like retinal tears or detachments. Prompt evaluation can prevent permanent vision damage, as early treatment for retinal issues significantly improves outcomes.