The experience of perceiving visual phenomena in darkness, often described as “red dots” or other light sensations, is a common occurrence. This article aims to explore the underlying reasons behind these visual experiences, providing clarity on a phenomenon many people encounter.
What You Are Seeing
The “red dots” or other light patterns seen in darkness are not external light sources but internal visual sensations. These phenomena are known as phosphenes, an entoptic phenomenon originating within the eye or brain. They can appear as flashes, spots, squiggles, or intricate patterns, often in red or orange hues. These perceptions arise from stimulating the retina or visual cortex, creating the illusion of light.
Common Explanations
Many instances of seeing internal lights in darkness stem from normal physiological processes. One common cause is pressure phosphenes, which occur when mechanical pressure is applied to the eye. This pressure, from rubbing eyelids or resting the eye against a pillow, directly stimulates retinal photoreceptor cells. These cells then send signals to the brain, interpreted as light. These sensations are transient and resolve once pressure is removed.
Another explanation involves spontaneous retinal activity, where cells like photoreceptors or ganglion cells can fire signals without light input. The visual system is active, and these cells sometimes generate random electrical impulses the brain processes as visual information. These firings are infrequent and produce fleeting visual dots or flashes.
For some, visual disturbances like flashes or geometric patterns can be part of an ocular migraine aura. This aura can occur with or without a headache and involves temporary neurological disturbances affecting vision. While different from benign phosphenes, these phenomena also originate internally due to changes in brain activity. Temporary changes in retinal blood flow can also lead to transient visual phenomena, as the balance of oxygen and nutrients to these cells is briefly altered.
When to Seek Medical Advice
While most internal visual phenomena are benign, certain characteristics warrant prompt medical evaluation. A sudden onset or significant increase in flashes and floaters, especially if accompanied by new floaters resembling cobwebs or a “curtain” obstructing vision, can signal a serious issue. These symptoms might indicate a retinal detachment, where the light-sensitive tissue pulls away from its supporting layers, or a posterior vitreous detachment, where the eye’s gel-like substance separates from the retina.
Persistent flashes of light (photopsia) are concerning if they occur in only one eye or with other visual disturbances. Such symptoms can indicate conditions requiring immediate attention to preserve vision. Associated symptoms like sudden vision loss, eye pain, or a severe headache alongside these phenomena also necessitate urgent medical consultation. Any new visual disturbances following head trauma or eye injury should always be evaluated. These signs are distinct from common, harmless phosphenes and suggest more significant ocular or neurological conditions.