What is the term for seeing colors when eyes are closed?

Phosphenes: Seeing Colors When Eyes Are Closed

Seeing colors when your eyes are closed is called phosphenes. This phenomenon refers to the perception of light or colors without any external light actually entering the eye 1.

What Are Phosphenes?

Phosphenes are visual sensations experienced as:

• Light flashes, colors, or patterns seen when no light is actually entering the eye 1, 2
• Can be experienced with closed eyes, in complete darkness, or in people with visual impairment 2
• May appear as colored lights, geometric patterns, or diffuse illumination 3

Mechanisms Behind Phosphenes

Several theories explain the physiological basis of phosphenes:

Biophoton Theory

• Phosphenes may result from ultra-weak photon emission (UPE) produced by cells in the visual system 3
• When this biophoton emission exceeds a certain threshold, it becomes a conscious visual sensation 2
• Cellular metabolic processes, particularly those involving free radicals and excited biomolecules, may generate these biophotons 3

Neuroanatomical Basis

• Both extrastriate visual cortical areas and primary visual cortex appear to be involved in phosphene perception 1
• Primary visual cortex (V1) activation is necessary for conscious phosphene perception 1
• Reentrant connections between extrastriate areas and primary visual cortex may play a crucial role 1

Neurotransmitter Involvement

• Glutamate-related processes may contribute to phosphene generation, particularly in cortical phosphenes 2
• Excess glutamate activity might increase ultra-weak photon emission in the occipital cortex 2

Types of Phosphenes

Phosphenes can be categorized based on their origin:

Spontaneous Phosphenes

• Occur without external stimulation 4
• Common in people with certain retinal diseases 4
• May be more frequent in dark environments or when eyes are closed 3

Induced Phosphenes

• Can be triggered by various stimuli:
  • Mechanical pressure on the eyeball 5
  • Electrical stimulation of visual cortex or retina 2
  • Magnetic stimulation (transcranial magnetic stimulation) 2
  • Eye movements (particularly in conditions like optic neuritis) 5

Clinical Significance

Phosphenes can have important clinical implications:

• May serve as a diagnostic sign in conditions like optic neuritis and multiple sclerosis 5
• Movement-induced phosphenes in optic neuritis share characteristics with Lhermitte's sign 5
• Can impact visual function testing in patients with retinal diseases 4
• May explain variability in visual function testing results in patients with retinal degeneration 4

Functional Imaging of Phosphenes

Functional MRI studies have shown:

• Bilateral activation across visual cortices during phosphene perception 4
• Different activation patterns during phosphene experiences compared to normal visual stimulation 4
• fMRI can be used to objectively document phosphene perception 4

Understanding phosphenes is important for both basic visual neuroscience and clinical applications, particularly in patients with visual system pathologies or those undergoing treatments like gene therapy for retinal diseases 4.