Pressure phosphenes are common visual sensations: perceptions of light or patterns without external light. They are triggered by mechanical pressure applied to the eye. Pressure phosphenes are considered harmless, representing a normal response of the visual system to physical stimulation.
Experiencing Pressure Phosphenes
Pressure phosphenes appear as transient flashes, swirling lights, various colors, or geometric patterns. These visual displays can range from simple bright spots to complex, deforming light grids with occasional dark spots. People frequently encounter these sensations when rubbing their eyes, applying gentle pressure to their eyelids, or experiencing a direct impact to the head, such as “seeing stars” after a bump.
The appearance of these phosphenes can differ between individuals. Some observe a diffuse colored patch that moves against the direction of rubbing, while others see well-defined shapes like bright circles. These visual events are brief, often persisting for only a few moments after the pressure is removed.
How Pressure Creates Light
The mechanism of pressure phosphenes involves the mechanical stimulation of cells within the retina, the light-sensitive tissue at the back of the eye. The retina contains photoreceptor cells, which convert light into electrical signals. Pressure applied to the eyeball physically deforms these cells or their associated structures.
This deformation generates electrical signals transmitted through the retinal ganglion cells. These cells process visual information and send it to the brain. The electrical impulses travel along the optic nerve to the visual cortex, the part of the brain responsible for interpreting visual information. The brain then interprets these signals as light, even though no actual light stimulation occurred.
When Visual Phenomena Need Attention
While pressure phosphenes are benign and temporary, certain other visual disturbances warrant medical evaluation. Unlike the brief, self-induced flashes of pressure phosphenes, persistent flashes of light that appear spontaneously, new or sudden increases in floaters (small specks or cobweb-like shapes drifting in vision), or a sudden shower of dots can be concerning.
A dark curtain or shadow moving across the field of vision also requires immediate medical attention. These symptoms could indicate a more serious condition, such as a retinal tear or retinal detachment, where the retina pulls away from its supporting tissue. Prompt consultation with an eye care professional is advisable if these persistent or sudden changes in vision occur to prevent potential permanent vision loss.