Why Do I See Light When I Close My Eyes in a Dark Room?

Hey there! Have you ever noticed those odd flashes, patterns or colors that appear when you close your eyes at night or in a dark room? If so, you‘re definitely not alone – in fact, visual experiences like these are super common.

In this guide, we‘ll dig into the science behind these bizarre lights we see with eyes closed. I‘ll explain what‘s actually going on in our vision system to produce these phenomena. Read on to uncover the mechanics behind phosphenes, floaters, visual snow, hypnagogic hallucinations and more!

What are Phosphenes?

The flashes of light many see when their eyes are closed are called phosphenes. These are characterized by seeing luminous shapes, spots, lines or blobs without any light entering the eyes. Most people have experienced phosphenes at some point, like when rubbing eyes, being struck in the eye, sneezing with eyes clenched shut, or standing up too quickly.

Phosphenes occur due to mechanical pressure, tension or movement on the eyeball. This stimulates the retina‘s photoreceptor cells, causing them to fire off signals to the visual cortex which gets perceived as flashes of light. Even though your eyes are closed, the visual system remains active and interprets these signals from the retina as light.

Some common ways phosphenes can be induced include:

• Rubbing eyes
• Being struck in the eye
• Forceful sneezing or coughing with eyes shut
• Quickly standing up, which shifts blood flow
• Migraines or headaches
• Eye injuries causing vitreous traction
• Eye surgery like LASIK or cataract surgery
• Vitreous detachment or shrinkage

Phosphenes themselves are mostly harmless – just the visual system doing its job in response to mechanical cues. But prolonged, recurrent or sudden phosphenes can potentially indicate an underlying medical condition.

What Produces Phosphenes When We Close Our Eyes?

To understand phosphenes, it helps to first learn a bit about eye anatomy and how we see.

Light enters the eye through the pupil and hits the retina – a thin layer of neural tissue lining the back of the eye. The retina contains photoreceptor cells called rods and cones. These convert the light into electrical signals that travel via the optic nerve to the visual cortex in the brain. The visual cortex interprets these signals to form the images we see.

Image source: Blausen Medical Communications

Even in darkness, the retina and visual system remain active. Pressing on the eyeball applies pressure on the retina, mechanically stimulating the rods and cones. They fire off electrical signals just like they would in response to light.

These signals propagate through the optic nerve to the visual cortex. Since the brain is receiving signals from the retina as if light is present, we perceive luminous flashes, shapes and colors – aka phosphenes!

Common Causes and Types of Phosphenes

Now let‘s explore some of the most frequent causes of phosphenes and how they stimulate the retina:

Rubbing Eyes

Rubbing eyes generates friction directly on the retina, especially in the peripheral visual field. This mechanically excites the rods and cones to transmit signals, causing a short-lived flash. The harder you rub, the more intense and prolonged the phosphene!

Migraines

Up to 60% of migraine sufferers experience visual disturbances like phosphenes and zig-zag patterns as part of the prodromal phase.

This visual aura happens because migraines involve vasoconstriction of blood vessels around the retina and optic nerve. The ischemic pressure stimulates the retina‘s photoreceptors into firing, which the brain perceives as shimmering lights or patterns.

Eye Injuries

A forceful blow to the eye can detach the vitreous humor from the retina, putting traction on it. This tugging action mechanically excites the retina, producing streaks of light across the visual field, like seeing "stars".

Vitreous Detachment

As we age, the vitreous gel in the eye liquefies and detaches from the retina. When it pulls away, it can stimulate the retina and cause prolonged, recurrent flashes of light.

Image source: Mayo Clinic

Visual Snow Syndrome

This chronic disorder causes a constant overlay of visual "snow" or static across one‘s field of vision. While its origins aren‘t fully understood, it‘s thought to arise from over-excitability of visual neurons. Those with visual snow also frequently report flickering lights.

Image source: atlasofopthalmology.net

Standing Up Quickly

Rapidly standing up shifts blood pressure and flow to the head. This transiently compresses retinal blood vessels, inducing phosphene flashes. These tend to be more pronounced in those with low blood pressure.

Pressure Phosphenes

Pushing on the eyes with hands or objects causes heightened pressure on the eyeball and retina, eliciting luminous shapes and colors that persist in the area of pressure. The phosphenes end once the pressure is released.

Entoptic Phenomena

This category includes phosphenes induced by light stimulating or interacting with the eye‘s structures. Examples are floaters, blue field entoptic phenomenon, self-light of the eye, and spontaneous retinal firing. These tend to manifest as webs, dots, rings and clouded areas.

How Common Are Phosphenes?

Phosphenes are an incredibly common experience – various surveys have found:

• 61% of people report seeing shapes and colors with eyes closed
• Up to 80% see phosphenes from pressure stimulation
• Over 90% perceive visual noise from ocular compression

So rest assured, those odd lights in the dark are a shared phenomenon and nothing to panic about!

Potential Phosphene Frequency Based on Age

This table summarizes studies on the prevalence of phosphenes across age groups:

Age Group	% Seeing Phosphenes	Study
18-24 years old	61%	Schankin et al, 2014
25-64 years old	54%	Ffytche et al, 2010
65-80 years old	35%	Ffytche et al, 2010

The data indicates phosphene frequency declines with age. This is thought to be because vitreous shrinkage and detachment occurs as we get older, making the retina less prone to mechanical stimulation.

When Should I Seek Medical Advice?

While mostly benign, certain phosphene characteristics warrant having your eyes examined:

✔️ Flashes only in one eye

✔️ Flashes last longer than a few seconds

✔️ Sudden increase in frequency or quantity of flashes

✔️ Flashes alongside large floaters or dark cobwebs

✔️ Flashing lights combined with other vision changes

✔️ Flashes accompanied by eye pain or headaches

These could potentially indicate an ocular disorder like:

• Retinal tear or detachment
• Vitreous detachment pulling on retina
• Ocular migraine
• Transient ischemic attacks
• Tumors compressing optic nerve
• Optic neuritis

Sudden flashes in particular should receive prompt medical attention to check for retinal detachment. Don‘t hesitate to get evaluated for peace of mind!

Fascinating Phosphene Facts

• Phosphenes can be seen even by those blind from eye disorders – showing they originate in the retina rather than visual cortex.

• While mostly random, phosphenes sometimes manifest as recognizable shapes, patterns or even faces!

• Phosphenes have inspired visual artists, who use techniques like eye-pressing to produce "prisoner‘s cinema" works.

• Hypnagogic hallucinations – where imagery is seen while falling asleep – are thought to be phosphene-related.

• The ancient oracle of Delphi may have used nerve gases to induce prophetic visions from phosphenes!

The Takeaway

Hopefully this guide has shed some light on those perplexing flashes we see when our eyes are closed! Phosphenes are quite common and usually nothing to worry about. But persistent or sudden-onset phosphenes could signal an underlying eye condition, so don‘t hesitate consulting your optometrist.

Our awesome visual system keeps humming even in the dark through phosphenes. While mostly random, these nighttime lights can serve as a reminder of our brain‘s ceaseless creativity. Sweet dreams!