Why You Might Be Seeing Stars

Seeing stars can be unsettling. Most of the time, it is nothing to worry about. But, in some cases, it may mean there is something wrong with your vision or eye health.

This phenomenon is known as photopsia. Symptoms of photopsia include seeing:

• Bands of light
• Colorful rings
• Flashing lights
• Sparks
• Stars

These visual disturbances are usually due to temporary physical pressure on the eyes—for example, rubbing your eyes or a hard sneeze.

However, it can also be a symptom of a medical issue, such as migraine headaches or a problem with the health or structure of the eye.

If you experience photopsia often or for extended periods of time, see your doctor. An optometrist or opthalmologist can give you a full eye exam and determine the cause.

This article discusses photopsia and five possible medical causes for seeing stars.

How Photopsia Occurs

When the retina (the lining in the back of the eye) senses light, it sends a message up the optic nerve to the brain. The brain then processes and identifies the image.

In photopsia, something other than visible light stimulates the retina. These artificial flashes of light are known as phosphenes.

Phosphenes can be triggered by applying pressure to the eyes or stimulating certain neurons in the eye or brain.

The most common cause of phosphenes is pressure on the eye. This can include rubbing the eyes, sneezing, or a blow to the head.

Photopsia can also be due to a medical condition. For example, low blood pressure, eye injury, diseases of the eye or brain, or migraines can cause you to see stars or flashes of light.

In addition, doctors can stimulate photopsia using a special type of ultrasound. This is sometimes used as a treatment for certain vision problems.

Pressure

Phosphenes caused by pressure can last for a few seconds. For example, you might see stars when you rub your eyes, sneeze, cough, or strain.

When phosphenes last longer than a few seconds or recur frequently, it could be a sign of a more serious issue.

Phosphenes can be caused by pressure inside the eye or brain. Possible reasons include:

• A blood vessel abnormality
• Infection
• Inflammation
• Injury
• Thyroid disease
• Tumor

Posterior Vitreous Detachment

Posterior vitreous detachment (PVD) is a common condition that is caused by aging.

The vitreous is a jelly-like substance that fills the center of the eye and gives the eyeball its shape. It is attached to the retina.

With normal aging, the vitreous becomes less firm and, in the process, can pull on the retina.

If the force of the pulling becomes strong enough, the vitreous may separate from the retina. When this occurs, it can cause a person to see floaters, flashes of light, or stars.

Photopsia caused by PVD is commonly seen as streaks of light, usually at the side of the field of vision, also known as peripheral vision.

Retinal Disorders

A problem with the retina can cause you to see stars, flashes, or bands of light.

A retinal detachment is one such condition. It occurs when the retina is pulled away from its normal position in the eye. Symptoms include:

• Flashes of light in one or both eyes
• A dark shadow that seems like a curtain covering part of your view
• An increase in floaters, which are small dark spots or squiggly lines that float across your field of vision

Symptoms of a detached retina come on quickly. If you experience these symptoms, see an eye doctor or go to the emergency room. A retinal detachment is a medical emergency. 

If a detached retina is not treated promptly, it can lead to further damage. In addition, a delay in treatment increases the risk of permanent vision loss or blindness. 

Other retinal conditions that affect the function of the eye can cause gradual vision loss. This can cause an effect known as visual snow, which is similar to seeing stars. These include:

• Diabetic retinopathy
• Macular degeneration
• Optic neuritis
• Retinitis pigmentosa

Certain medications also can alter the function of the retina in ways that produce phosphenes. One such drug is Corlanor (ivabradine), which is used to treat tachycardia (rapid heart rate).

Migraines

Visual changes known as auras are a common symptom of migraine headaches. An aura typically lasts about 20 to 30 minutes and then goes away on its own, without any treatment.

With some migraines, a visual aura may occur without head pain. These are called ocular migraines. The aura can affect one or both eyes and can appear as:

• Prismatic colors, meaning similar to a rainbow
• Flashes of light
• Stars
• Zig-zag lines
• Blind spots

If a headache follows the flashes, the episode is diagnosed as a migraine headache. However, if these flashes or lines of light occur without a headache, it is often described as a migraine without a headache.

Impaired Visual Function in the Brain

While less common, phosphenes can occur due to dysfunction of the visual areas of the brain. This may occur as a result of a lack of blood flow or damage to the brain.

Cerebrovascular disease (blood vessel disease in the brain) or systemic low blood pressure can result in reduced blood supply to the brain, and consequently, diminished brain function.

Orthostatic hypotension, also called postural hypotension, is a sudden drop in blood pressure. This typically occurs when someone who already has high or low blood pressure rapidly moves from lying down or sitting to standing up.

This drop in blood supply can briefly impair brain function, causing flashing lights or similar phenomena for a few seconds.

Summary

The phenomenon of seeing stars is known as photopsia. The individual flashes of lights are called phosphenes.

Phosphenes occur when pressure on the eye stimulates the retina. The retina is a light-regulating structure in the eye. Pressure can be caused by an external force, such as rubbing your eyes, or internal inflammation.

Photopsia can also occur with migraines, changes in blood pressure, a lack of blood flow to the brain, or brain damage.

Photopsia is usually harmless. However, if you see frequent flashes of light, it can be a warning sign of something more serious. If you experience this, talk to your doctor.