Several different issues may cause a person to 'see stars,' and many of them are no cause for concern. An isolated flash of light is usually harmless.
However, if seeing stars becomes frequent or is severe and sudden, a person should speak to an eye doctor right away.
How does seeing stars work?
A person typically sees stars because of a disturbance in the retina or the brain.
The retina's role
Seeing stars may be caused by an inflammed retina.
The retina is a lining of cells that sits at the back of the eye and sends messages to the brain when it detects light.
The retina does not see colors or shapes; it only sees light. A special gel called the vitreous sits in front of the retina to protect it.
If the retina gets inflamed, or the vitreous gel moves around or shrinks, the retina will be stimulated and send signals to the brain. The brain interprets these signals as light, even if no external light source exists.
The brain's signals
The brain takes signals from the retina and interprets them as light using electrical impulses.
If something disrupts electrical activity in the brain, it may send false signals, making a person think they see stars.
The following are the most common causes of disruptions in the brain or retina that could lead to seeing stars:
1. A blow to the head
A blow to the head may lead to seeing stars.
Cartoons have portrayed this phenomenon for years: if someone gets hit on the head, they see stars.
The brain is protected by a layer of fluid that usually prevents it from hitting the inside of the skull. A hard knock, such as from a sports collision or car accident, however, may result in the brain bouncing against the skull.
The back of the brain contains the occipital lobe, which is the part of the brain that processes visual information. If this area is knocked, it sends out electrical signals that the brain thinks are light.
Getting hit in the eye can also cause flashes of light because it bumps the retina. The retina is stimulated and sends light signals to the brain. Gently rubbing closed eyes is one way to experience this phenomenon without injury.
Migraine headaches can cause changes in vision, including seeing stars, sparkles, or flashes. They can also cause spots, heat-like waves, tunnel vision, or zigzagging lines.
These changes occur in both eyes and are thought to be caused by abnormal electrical signals in the brain.
If these visual changes occur before a headache develops, it is called migraine with aura. Some people who get migraines may also experience the aura without a headache afterward.
A retinal migraine is a different type of headache that causes visual changes in one eye only. This is a rare condition and can be a symptom of something more serious. Like a migraine with aura, the visual changes happen before the headache hits.
The visual changes may include seeing stars, flashes, or dark spots, as well as temporary blindness. Retinal disturbances or decreased blood flow to the retina may cause these symptoms.
It is essential for people to contact a doctor right away if they experience retinal migraine symptoms.
Other typical migraine symptoms include:
- throbbing and severe headache
- sensitivity to light and sound
3. Movement in the eye's vitreous gel
The vitreous gel that is in front of the retina can move around, sometimes pulling on the retina itself. This causes the retina to send light signals to the brain.
Movement or changes in the vitreous become more common as people age and are typically harmless.
However, these flashes could signal a serious issue if:
- they are happening frequently and regularly
- they come on suddenly and severely
- they are accompanied by other vision changes, such as new floaters or cloudiness
4. Retinal detachment or torn retina
Sometimes, the vitreous gel pulls on the retina hard enough to cause damage. It may tear the retina or detach it from the back of the eye.
If this happens, a person may see:
- a sudden appearance of stars or flashes
- blurred vision
- loss of peripheral vision
- a curtain or shadow across the vision
Risk factors for retinal detachment or tearing include:
- being over age 40
- a family history of retinal detachment
- a previous retinal detachment or torn retina
- being very nearsighted
- previous cataract surgery
- having another eye disease, disorder, or injury to the eye
A torn or detached retina needs emergency medical care. It may be corrected with surgery, but can lead to blindness if left untreated.
Flashes vs. floaters
Flashes of light or seeing stars in vision should not be confused with floaters. While seeing stars may sometimes accompany floaters, these two things are caused by different factors.
Floaters may look like shadows, lines, or dots that move across a person's field of vision. They can be caused by:
- protein clumps or cells in the vitreous
- tiny blood vessels bursting in the eye
Floaters are typically harmless and become common as a person ages. However, a person should still discuss the floaters with an eye doctor, especially if they happen frequently or come on suddenly.
Tips for healthy eyes
An eye exam before the age of 40 is recommended for everyone.
Seeing stars on occasion is often a natural part of aging and cannot be prevented. However, certain lifestyle factors can help keep eyes healthy for as long as possible.
To keep the eyes healthy, a person should:
- Eat a nutritious diet that includes fruits, vegetables, whole grains, and lean proteins.
- Quit or avoid smoking. Smoking is a significant risk factor for macular degeneration, which can lead to blindness.
- Always wear sunglasses with UV protection when in the sunlight.
- Wear proper eye protection when using power tools and during contact sports.
- Take breaks from looking at a computer or television screen every 20 minutes.
Seeing occasional flashes or stars in vision is usually not an indication of an underlying health problem.
Many people find that seeing stars happens only occasionally and that their eyes are otherwise healthy. Seeing stars may occur more often with age.
However, seeing flashes frequently can indicate an eye problem that needs medical treatment. If a person experiences a rapid onset of flashes, stars, or any other sudden vision changes, they should seek medical care right away.
The American Academy of Ophthalmology recommend people get a comprehensive eye exam by age 40 even if they have no other health problems.
Some people will need to get an exam sooner if they have diabetes, high blood pressure, or a family history of eye disease. People with poor vision may also be offered a comprehensive eye exam during their regular checkup.
These appointments are a good time to mention seeing any stars or flashes and to discuss any tests or treatments with a doctor to maintain healthy eyes for years to come.