Perceiving colors, especially red, when your eyes are closed is a common experience. These visual sensations are a normal physiological occurrence, resulting from how your eyes and brain process internal signals and ambient light.
The Phenomenon of Phosphenes
The visual sensations observed with closed eyes are called phosphenes. These are perceptions of light without actual light entering the eye, manifesting as various shapes, colors, or flashes that are typically temporary. Mechanical phosphenes are one common type, occurring when physical pressure is applied to the eye, such as gently rubbing your closed eyelids. This pressure stimulates retinal photoreceptor cells, mimicking light and causing you to “see stars” or other patterns.
Beyond mechanical stimulation, phosphenes can also arise spontaneously from the baseline activity of retinal cells or other parts of the visual system. Even without external light, light-sensitive photoreceptors in your retina can generate electrical signals. These internal signals are then interpreted by the brain as visual phenomena. This spontaneous activity contributes to the varied and sometimes abstract patterns seen in darkness.
The Role of Eyelids and Light
The frequent perception of red with closed eyes relates directly to your eyelids’ unique properties and their interaction with ambient light. Eyelids are not completely opaque; they allow some light to pass through, even when closed. Research indicates the eyelid acts as a filter, significantly attenuating blue and green light while allowing a higher percentage of red light to transmit. Studies estimate only about 0.3% of blue and green light passes through, compared to approximately 5.6% of red light.
This preferential transmission of red light is due to the eyelids’ vascularity, or presence of tiny blood vessels. Hemoglobin, the protein in red blood cells that carries oxygen, strongly absorbs shorter wavelengths like blue and green. Longer wavelengths, such as red light, are absorbed less effectively by hemoglobin and pass through the blood-rich tissue more readily. Consequently, the light reaching your retina after filtering through your eyelids is predominantly reddish, creating the common perception of a red or orange hue.
When to Seek Medical Advice
While seeing red or other patterns with closed eyes is generally normal and harmless, certain visual phenomena warrant attention from an eye care professional. If you suddenly experience new flashes of light—especially if persistent, increasing in frequency or intensity, or accompanied by other symptoms—seek prompt medical evaluation. These changes could signal underlying issues like posterior vitreous detachment, where the eye’s gel-like substance separates from the retina, or more serious conditions such as a retinal tear or detachment.
Similarly, a sudden increase in floaters—small specks, lines, or cobwebs that drift across your vision—should prompt a visit to an ophthalmologist. While floaters are often a normal part of aging, a sudden onset can be a warning sign of retinal problems. Any vision loss, or a sensation of a “curtain” or shadow in your visual field, also requires immediate medical attention. Early diagnosis and treatment are important for preserving vision.