Experiencing bright light even when your eyes are closed is a common and generally normal phenomenon. It can arise from various sources, and understanding these origins can help explain the experience.
External Light Passing Through Eyelids
External light sources can be perceived even with closed eyelids because eyelids are semi-translucent. This allows some light to reach the retina. The amount of light that passes through varies based on wavelength and individual characteristics like eyelid thickness.
Red light penetrates more easily than blue or green light. This preferential filtering of longer wavelengths (reds and oranges) explains why you often see a reddish or orange hue when facing a bright light source, like the sun, with your eyes closed. This color results from light filtering through the blood vessels in the eyelids.
Internal Light Perceptions and Phosphenes
Sensations of light can also originate from within the eye or brain, a phenomenon known as phosphenes. Phosphenes are flashes or patterns of light perceived without external light entering the eye. These are normal and reflect the visual system’s inherent activity.
One common cause of phosphenes is mechanical stimulation, such as rubbing your eyes. Pressure on the eyeball stimulates the retina and optic nerve, causing flashes or swirls of color. Phosphenes can also occur due to spontaneous retinal activity, where retinal cells generate electrical signals even in darkness. This “neural noise” is a normal part of visual system operation.
Rapid eye movements (saccades) can also induce brief flashes. The brain interprets these internal signals as various visual experiences, such as dots, squiggles, or geometric patterns.
When to Be Concerned About Light Perceptions
While most instances of perceiving light with closed eyes are harmless, certain patterns or accompanying symptoms warrant medical attention. A sudden onset of new, persistent flashes of light, especially if frequent, can indicate a posterior vitreous detachment, where the vitreous gel pulls away from the retina.
If these flashes are accompanied by a sudden increase in floaters (small specks or lines drifting in your vision), it is particularly concerning. Flashes coupled with a loss of peripheral vision or a sensation of a “curtain” or shadow blocking part of your visual field require immediate evaluation. These symptoms could signal a retinal tear or detachment, which are medical emergencies that can lead to permanent vision loss if untreated. Consult an eye care professional promptly for any significant changes in light perceptions.