Flashes of light refer to transient perceptions of light that appear without an external source. These visual phenomena can manifest as lightning bolts, streaks, stars, or tiny pinpoints of light, often more noticeable in dim environments. While they can range from harmless occurrences to indicators of serious underlying conditions, understanding their potential causes is important for proper evaluation.
Common Explanations for Flashes
Some flashes are often harmless and resolve on their own. For example, rubbing your eyes can stimulate the retina, causing you to see phosphenes, which are harmless bursts of light that disappear within seconds. Similarly, a sudden drop in blood pressure upon standing up quickly, known as orthostatic hypotension, can lead to brief flashes or sparkles due to reduced oxygen flow to the retina. This “seeing stars” effect is temporary and resolves as blood pressure stabilizes.
Migraine aura is another common cause of visual flashes, preceding a headache. These visual disturbances can include shimmering zigzag lines, bright colored spots, or flashing lights that last between 10 to 60 minutes. The “classic” migraine visual aura begins as a central crescent-shaped shimmering blind spot that expands outwards. As the eye ages, the vitreous gel can undergo changes, a process called vitreous syneresis. This can cause the gel to gently pull on the retina, leading to flashes, often described as a camera flash in peripheral vision, which are more noticeable in dimly lit settings.
Concerning Medical Conditions
While some flashes are benign, others can signal more serious medical conditions requiring prompt attention. Posterior Vitreous Detachment (PVD) is a common age-related change where the vitreous gel separates from the retina. This separation can cause flashes, often described as lightning streaks or camera flashes in the peripheral vision, and is frequently accompanied by new floaters. While PVD itself is not sight-threatening, it can sometimes lead to complications such as retinal tears.
A retinal tear occurs when the vitreous gel pulls forcefully on the retina, causing a break in the light-sensitive tissue. The flashes associated with a retinal tear may be more intense, persistent, or accompanied by a sudden increase in floaters, sometimes described as a “shower” of black specks. If a retinal tear is left untreated, fluid can seep through the tear, causing the retina to lift away from its underlying supportive tissue, a condition known as retinal detachment. Retinal detachment is a medical emergency where flashes can be a symptom, often alongside a dark “curtain” or “shadow” obscuring part of the vision that does not resolve.
Vitreous hemorrhage involves bleeding into the vitreous gel, which can cause sudden vision changes including flashes, blurred or hazy vision, and an increase in floaters. This bleeding can result from various causes, such as diabetic retinopathy, eye injury, or a retinal tear, and can significantly impair vision depending on the amount of blood. Any sudden onset of these symptoms warrants a thorough eye examination to determine the underlying cause and prevent potential vision loss.
When to Seek Urgent Medical Care
It is important to seek immediate medical attention from an eye care professional, such as an ophthalmologist, if you experience sudden or concerning flashes. This is particularly true if the flashes are new, frequent, or bright, especially in one eye. A sudden increase in new floaters, described as “soot” or a “shower” of dots, accompanying the flashes is also a strong indicator for prompt evaluation.
Medical care is also necessary if flashes are accompanied by a shadow, curtain, or partial loss of vision, as these can be signs of a retinal detachment. Any flashes occurring after a head injury or eye trauma should be assessed immediately. Persistent or worsening flashes, regardless of other symptoms, also warrant a professional eye examination. Early diagnosis and appropriate treatment are important to preserving vision in serious eye conditions.