Seeing lights or flashes in the corner of your eye can be startling. While this phenomenon, medically known as photopsia, often stems from harmless causes, it can sometimes signal a more serious underlying condition that requires prompt medical attention. Understanding the characteristics of these visual sensations and their potential origins is important for eye health.
Types of Visual Sensations
Visual sensations can manifest in several ways, and recognizing the specific type can offer clues about their cause. Flashes, or photopsia, are perceptions of light that are not caused by external light sources. These can appear as sudden streaks of lightning, bright spots, or flickering lights, often noticed in the peripheral vision. They typically last for a few seconds or minutes.
Floaters, known medically as myodesopsia, are small specks, threads, or cobweb-like structures that drift across the field of vision. These shapes move with eye movements but tend to drift slowly when the eye stops, making them difficult to focus on. Shimmering or wavy lines, often described as zigzag patterns or heatwaves, can also occur, sometimes affecting both eyes.
Common and Benign Causes
Many instances of seeing lights in the corner of the eye arise from common and generally benign conditions. A frequent cause is posterior vitreous detachment (PVD), an age-related process where the vitreous humor, the gel-like substance filling the eye, naturally shrinks and separates from the retina. As the vitreous detaches, it can tug on the retina, which interprets this mechanical stimulation as flashes of light. PVD often leads to new floaters as collagen fibers within the vitreous clump together, casting shadows on the retina. While the flashes may be brief, floaters can persist, though the brain often learns to ignore them over time.
Another cause of visual disturbances is ocular migraine, also known as migraine with aura without headache. This condition involves temporary visual symptoms, such as shimmering zigzag lines, blind spots, or flashing lights, that can affect one or both eyes. Ocular migraines are thought to occur due to temporary changes in blood flow to the eye or abnormal electrical activity in the brain’s visual pathways. These visual phenomena typically resolve within 10 to 60 minutes.
Sometimes, simply rubbing one’s eyes or experiencing pressure on the retina can cause flashes of light. This occurs because the retina, the light-sensitive tissue at the back of the eye, responds to any form of stimulation, including pressure, by sending signals that the brain interprets as light. Eye strain or fatigue can also contribute to transient visual disturbances.
Urgent Causes and Warning Signs
While many visual sensations are harmless, some can indicate serious eye conditions that require immediate medical attention. Retinal detachment is a medical emergency where the retina pulls away from its normal position at the back of the eye, separating it from the blood vessels that supply it with oxygen and nutrients. This can lead to permanent vision loss if not treated promptly. Symptoms often include a sudden increase in floaters, flashes of light, and the sensation of a dark curtain or shadow moving across the field of vision. The flashes in retinal detachment are often described as streaks of lightning and may be more noticeable in the peripheral vision.
A retinal tear, which can precede a full detachment, also causes flashes and a sudden shower of new floaters due to the vitreous tugging on the retina. If a tear forms, fluid can seep under the retina, leading to detachment. Vitreous hemorrhage, or bleeding into the vitreous gel, is another serious cause of visual disturbances. Symptoms include sudden blurred vision, new floaters that can appear as black specks or strings, and flashes of light. This bleeding can block light from reaching the retina, causing vision problems.
It is important to seek immediate care if any of these “red flag” symptoms occur: a sudden onset of new floaters, a significant increase in their number, a shower of new floaters, a sudden onset of flashes, or the appearance of a dark curtain or shadow obstructing vision. These signs may indicate a retinal tear, retinal detachment, or vitreous hemorrhage, all of which necessitate urgent evaluation by an eye care professional.
What to Expect at the Doctor’s Office
When experiencing new or concerning visual symptoms like flashes or floaters, a visit to an eye care professional is important. The doctor will typically perform a comprehensive eye examination, which often includes a dilated eye exam. During this procedure, special eye drops are administered to widen the pupils, allowing the doctor a clearer and more extensive view of the internal structures of the eye, particularly the retina and optic nerve. This process helps in identifying any tears, detachments, or other abnormalities that might be causing the symptoms.
The eye care professional will meticulously examine the back of the eye using specialized equipment, asking the patient to look in various directions to ensure a full view. They may also use other diagnostic tools, such as optical coherence tomography, to visualize the retinal layers and blood vessels. The examination is generally painless, though the dilating drops may cause temporary light sensitivity and blurred vision for several hours. Based on the findings, the doctor can provide a diagnosis, ranging from reassurance that the condition is benign, such as a complete PVD, to identifying a serious issue requiring prompt treatment or ongoing observation.