It is common to occasionally see sudden flashes of light in your vision. Often described as streaks, sparkles, or lightning bolts, these flashes can be startling. While concerning, they are frequently harmless. However, flashes can signal a more significant eye condition. This article explores reasons for flashes, from benign to those needing medical attention.
Common and Harmless Explanations
One frequent cause of flashes is Posterior Vitreous Detachment (PVD). As people age, the vitreous gel, a clear, jelly-like substance filling the eye, shrinks and pulls from the retina. This pulling on the retina stimulates it, creating flashes, especially in peripheral vision. PVD is a normal age-related change and often benign; initial flashes signify this separation.
Ocular migraines, or migraine auras, are another common visual phenomenon. These neurological events cause temporary visual disturbances like shimmering lights, zigzags, or blind spots. They may precede, accompany, or occur without a headache (silent migraine). Visual changes stem from temporary shifts in brain blood flow or electrical activity, not an eye problem.
Sometimes, flashes can be linked to sudden blood pressure changes. For instance, orthostatic hypotension (a sudden drop in blood pressure upon standing) can temporarily reduce blood flow to the brain and eyes. This momentary reduction might cause a brief “white out” or flash. These instances are fleeting and resolve quickly as blood flow normalizes.
Applying pressure to the eye can create temporary light sensations called pressure phosphenes. Rubbing or pressing your eyes stimulates photoreceptors (light-detecting cells in your retina). This mechanical stimulation generates electrical signals your brain interprets as light, even without actual light entering the eye. These flashes are momentary and cease once the pressure is removed.
Eye Conditions That Cause Flashes
Flashes can indicate serious eye conditions requiring prompt medical evaluation. A retinal tear or detachment is a significant concern where the retina, the light-sensing tissue at the back of the eye, pulls away. Flashes with a retinal tear or detachment are often sudden, persistent streaks, resembling lightning bolts or camera flashes. These flashes differ from benign PVD flashes by being more intense or appearing consistently in a specific visual field.
A vitreous hemorrhage occurs when blood leaks into the vitreous gel, causing flashes and new floaters. This bleeding often results from a retinal tear damaging a blood vessel, or from abnormal blood vessels in conditions like diabetic retinopathy. Blood in the vitreous can obscure vision and stimulate the retina, leading to flashes. Prompt diagnosis and treatment are important to address the underlying cause and preserve vision.
Acute angle-closure glaucoma is a less common but severe eye condition that can cause flashes or halos around lights. It involves a sudden, rapid increase in eye pressure, causing significant eye pain, blurred vision, and redness. Elevated pressure can compromise the optic nerve and, at times, stimulate the retina or optic nerve to produce light sensations. This is a medical emergency due to potential for rapid, irreversible vision loss.
Other less common eye issues can contribute to flashes. For example, uveitis (inflammation inside the eye) can irritate the retina or other structures, leading to visual disturbances including flashes. Optic neuritis, an optic nerve inflammation, can also cause flashes, especially with eye movement, along with pain and vision loss. While less frequent causes of isolated flashes, they highlight the importance of a comprehensive eye examination.
When to Seek Medical Attention
Seek immediate medical attention for “red flag” symptoms with flashes. These include a sudden onset of new flashes, especially with a sudden increase in floaters (small specks or cobwebs). Consult an ophthalmologist or emergency room if you notice a shadow, curtain, veil, or loss of peripheral vision. Any significant eye pain or vision changes after head trauma also need urgent evaluation.
Prompt attention (within 24 to 48 hours) is advisable if flashes are persistent, new, or concerning, even without alarming symptoms. This includes flashes occurring regularly or representing a noticeable change. An eye care professional can assess if flashes are part of a benign process, like early PVD, requiring monitoring. Early evaluation helps identify developing issues before they become serious.
Regular comprehensive eye exams are important, especially as you age. These check-ups allow an eye doctor to monitor eye health, including the vitreous and retina, and detect conditions like PVD early. Consistent eye care helps understand normal eye changes and provides a baseline if new symptoms arise.
For flashes, the doctor will likely perform a dilated eye exam. This involves eye drops to widen pupils, allowing a clear view of the retina and vitreous gel at the back of the eye. This inspection helps determine the cause of flashes and if intervention or monitoring is necessary. The doctor may also use other diagnostic tools to assess eye structures.