When people rub their eyes, they often notice a curious display of swirling colors, bright spots, or geometric patterns, even in complete darkness. This phenomenon is a natural response of the visual system.
How Pressure Creates Light Sensations
The light sensations observed when rubbing the eyes stem from a mechanical stimulation of the visual system. The eye contains a light-sensitive layer at the back called the retina, which is lined with specialized cells known as photoreceptors. These cells are designed to convert light energy into electrical signals that the brain can interpret.
When external pressure is applied to the eyeball, such as from rubbing, this mechanical force deforms the retina and its photoreceptors. This physical deformation triggers the photoreceptors to generate electrical impulses, much like they would if actual light were entering the eye. These electrical signals then travel along the optic nerve to the brain’s visual processing centers. The brain, accustomed to interpreting such signals as light, processes these pressure-induced impulses as visual perceptions, even though no external light source is present.
The Visual Experience of Phosphenes
The internally generated light sensations seen when rubbing the eyes are known as phosphenes. The term “phosphene” originates from Greek words meaning “light” and “to show,” aptly describing these perceptions of light without an external light source.
These visual manifestations can take various forms, commonly appearing as luminous stars, zigzag patterns, spirals, or diffuse colored blobs. Phosphenes are transient, typically subsiding quickly within a few seconds after the pressure is removed. The characteristics of these patterns, including their colors and shapes, can vary from person to person. They are a subjective experience produced entirely within the visual system.
When Visual Disturbances Need Attention
While the phosphenes caused by eye rubbing are a normal and harmless occurrence, other types of visual disturbances can signal underlying medical issues that require professional attention. The key distinction is that phosphenes from eye rubbing are directly linked to physical pressure and disappear when it’s removed.
However, spontaneous flashes of light, especially if they occur without eye rubbing, warrant immediate evaluation by an eye care professional. Similarly, a sudden appearance or increase in the number of floaters, which are small specks or cobwebs drifting in vision, can be concerning. Other symptoms that necessitate prompt medical attention include a dark curtain or shadow moving across the field of vision, blurred vision, or eye pain. These symptoms could indicate serious conditions such as a retinal tear or detachment, which, if left untreated, can lead to permanent vision loss.