Seeing a circle when blinking is a common visual experience. This perception of a circular shape or pattern in one’s vision is particularly noticeable during or immediately after closing and opening the eyes. While often harmless, this sensation can sometimes indicate an underlying condition requiring medical attention. Understanding the various reasons behind these circles helps differentiate between benign occurrences and those needing professional evaluation.
Harmless Explanations for Seeing Circles
One common reason for perceiving circles when blinking involves pressure phosphenes. These visual sensations occur when mechanical pressure, such as gently rubbing the eyelids, stimulates the light-sensitive cells of the retina. This stimulation creates the perception of light, often appearing as shimmering patterns or circular shapes, even in the absence of actual light. The pressure temporarily activates the photoreceptors, leading the brain to interpret this activity as light.
Another frequent cause is the persistence of afterimages. When someone looks at a bright light source or a strongly contrasting image, the photoreceptor cells in the retina can become temporarily overstimulated. After looking away or blinking, this temporary imprint can remain in the visual field, often manifesting as a ghost-like or circular shape with colors complementary to the original stimulus. These afterimages typically fade within seconds to minutes as the retinal cells recover their normal sensitivity.
Small specks or strands that drift across the field of vision, known as floaters, can also sometimes appear as circular or C-shaped forms, particularly a type called a Weiss ring. These floaters are microscopic clumps of collagen fibers or other cellular debris within the vitreous humor, the jelly-like substance that fills the eye. As people age, the vitreous gel can liquefy and shrink, causing these fibers to condense and cast shadows on the retina. While often benign and a normal part of the aging process, new or sudden onset floaters can sometimes indicate a more significant issue.
When a Circle Signifies a Potential Issue
The sudden appearance of new floaters, especially if accompanied by flashes of light or a dark, curtain-like shadow in the vision, can signal a retinal tear or detachment. In these situations, the vitreous gel may pull on the retina, creating a tear that allows fluid to pass underneath, potentially lifting the retina from its supporting tissue. Such events are medical emergencies that, if left untreated, can lead to permanent vision loss.
Some individuals experience visual disturbances, including shimmering circles or zigzags, as part of a migraine aura. This aura typically precedes a migraine headache and is caused by temporary changes in brain activity in the visual cortex. The visual effects can start as a small blind spot or a shimmering C-shape that gradually expands across the field of vision. While usually benign, these visual phenomena are distinct from other causes of visual circles.
In rarer cases, visual disturbances resembling circular or shimmering blind spots can occur without a headache, sometimes called ocular or retinal migraine. These episodes involve temporary reductions in blood flow to the retina or visual pathways. Visual symptoms are typically transient, lasting minutes to an hour, and can affect one or both eyes. While not indicative of severe eye disease, these episodes should still be evaluated by an eye care professional.
Temporary visual disturbances, including spots or circles, can also link to sudden blood pressure fluctuations. Significant drops or spikes can momentarily affect retinal blood flow, leading to transient visual changes. This is often observed when standing up too quickly, causing a temporary decrease in blood pressure to the brain and eyes. These visual effects are usually short-lived and resolve as blood pressure stabilizes.
Seeking Medical Evaluation
Seeking medical evaluation for seeing circles is crucial, as early diagnosis prevents serious vision problems. Consult an eye care professional immediately for a sudden onset of new floaters, especially if numerous or with flashes of light. A dark shadow or “curtain” across your vision, or any sudden vision loss, also warrants urgent medical attention. Persistent circles not explained by benign causes like afterimages or pressure phosphenes should also be evaluated.
During an eye examination, an optometrist or ophthalmologist performs a comprehensive assessment. This often includes a dilated eye exam, using eye drops to widen pupils for a clear view of the retina and vitreous humor at the back of the eye. They may also conduct a visual field test to check for any blind spots or reduced vision. Additional tests like optical coherence tomography (OCT) or ultrasound might further investigate retinal and optic nerve health.
Timely diagnosis and treatment are important for conditions causing visual circles, especially those affecting the retina. For instance, an early retinal tear might be treated with laser or cryopexy to prevent it from progressing to a full detachment. If a retinal detachment occurs, surgical intervention is often necessary to reattach the retina and preserve vision. Prompt action can significantly improve outcomes and maintain long-term eye health.