Seeing black dots or other shapes when closing your eyes is a common experience. While sometimes unsettling, these visual sensations are often a normal and harmless part of how our visual system functions. Understanding their common causes can help alleviate concerns.
Common Explanations for Dots
Vitreous floaters are a common cause of floating specks or lines. The vitreous, a clear gel filling your eye, changes with age. Collagen fibers within it can clump, casting tiny shadows on the retina. These shadows are perceived as floaters, appearing as black or gray specks, threads, or cobwebs that drift across your vision. They are often more noticeable against a plain, bright background.
Phosphenes are sensations of light generated from within the eye or brain, not external sources. They commonly occur when pressure is applied to the eyeball, such as by rubbing your eyes. This mechanical stimulation activates retinal cells, causing brief flashes or patterns of light. Sneezing, coughing, or quick changes in blood pressure can also induce phosphenes.
Afterimages can also cause dots or patterns when closing your eyes. They result from temporary fatigue of retinal photoreceptor cells after exposure to a bright image. For example, staring at a bright light and then closing your eyes might leave a lingering impression. This occurs as visual system cells become less responsive after prolonged stimulation.
Identifying Warning Signs
While many visual disturbances are benign, certain symptoms warrant prompt medical evaluation. A sudden, significant increase in the number or size of floaters can be a warning sign, indicating an issue needing urgent attention.
New floaters appearing with flashes of light are particularly concerning. These flashes, like lightning streaks or bright sparks, occur when the vitreous gel pulls on the retina. Strong pulling can cause a retinal tear.
A dark “curtain” or “shadow” obscuring part of your vision is another serious symptom. This shadow may start in peripheral vision and gradually expand, potentially indicating a retinal detachment. Any sudden, significant vision loss also requires immediate medical attention. These symptoms, if persistent or worsening, should prompt an urgent visit to an eye specialist.
Potential Medical Reasons
Several medical conditions can cause concerning visual phenomena. A retinal detachment or tear is a serious condition where the retina pulls away from the back of the eye. This can occur if the vitreous gel, shrinking with age, tugs on the retina forcefully enough to create a tear. Untreated retinal detachment can lead to permanent vision loss as the retina loses its blood supply.
Posterior Vitreous Detachment (PVD) is a common, age-related process where the vitreous gel separates from the retina. While often harmless, PVD can cause floaters and flashes as the gel pulls away. In some instances, this pulling can lead to a retinal tear, potentially progressing to a retinal detachment.
Ocular migraines, a rare type of migraine, cause visual disturbances in only one eye. Symptoms include temporary blind spots, zigzagging patterns, or shimmering lights, often preceding a headache. These visual symptoms typically last between 5 to 60 minutes.
Vitreous hemorrhage, or bleeding into the vitreous, can cause floaters or general vision clouding. This can result from conditions like diabetic retinopathy, where abnormal retinal blood vessels bleed. Eye trauma or retinal tears can also lead to vitreous hemorrhage.
Inflammation or infection within the eye, such as uveitis, can also cause floaters. This happens when inflammatory cells enter the vitreous, casting shadows perceived as floating specks. Such conditions require diagnosis and treatment by an eye care professional to prevent complications.