Have you noticed flashes or threads of light in the corners of your eye and wondered what’s going on? Flashes in your eye are a type of photopsia, or vision disturbance.

Flashes of light can happen in one or both of your eyes and have different shapes, colors, frequency, and duration. There are many causes for this.

Let’s take a closer look at the causes of light flashes in your eye and what you can do about them.

Let’s consider the function of the retina and vitreous humor to better understand these flashes.

  • The retina is a thin light-sensitive tissue that lines the back of the inside of your eye. It transmits electrical signals to your brain via the optic nerve. The job of the retina is to process the focused light that comes in through your pupil and to let your brain convert this information into a picture.
  • The vitreous humor is a clear jelly-like fluid that takes up a large part of the back of your eye. It protects the retina and helps your eye maintain its shape.

While there are many reasons you may see flashes of light in your eye, pressure or force on the retina are most often the causes. These flickers of light happen in the back part of your eye where the retina’s located.

Tiny fibers float in the vitreous fluid and are attached to the retina. When these fibers get pulled or rubbed, it can cause flashes or light sparks from the friction.

Flashes of light in the eye are typically not a condition on their own. Instead, they tend to be a symptom of another condition.

What are the possible causes?

According to the American Academy of Ophthalmology, seeing flashes of light in the corner of your eye can be caused by a variety of factors or conditions. Some causes may be related to your eye health, while others may be related to other types of health conditions.

Several types of eye-related issues may cause flashes of light to appear in the corner of your eye or field of vision.

Eye-related causes

  • Posterior vitreous detachment. This is one of the most common causes of flashes of light in your eye. It typically happens as you get older. With posterior vitreous detachment, the vitreous humor detaches from the retina. If it happens too quickly, it can cause small flashes of light, usually in the corner of your vision. It can also cause floaters. This condition doesn’t usually require treatment.
  • Optic neuritis. Optic neuritis happens when the optic nerve becomes inflamed. This can be caused by an infection or a nerve-related disorder such as multiple sclerosis. Flashes of light can be a symptom of this condition.
  • Retinal detachment. Retinal detachment is a serious condition that can cause partial or complete loss of vision. When this happens, the retina detaches, shifts, or moves away from the back wall of the eye.
  • Pressure on the retina. If you rub your eyes, cough too hard, or get hit on the head, you may notice flashes of light due to extra pressure on the retina.
Healthline

Flashes of light in your eye may not necessarily be caused by an eye-related issue. It may be a symptom of a different health condition.

Other health-related causes

  • Occipital epilepsy. This rare type of seizure in the occipital lobe of the brain can cause visual flashes in the eye. It can be a sign of seizure activity. This is sometimes mistakenly diagnosed as a migraine aura. Typically, though, occipital epilepsy is shorter (2 minutes) compared to a migraine aura (15 to 60 minutes).
  • Migraine. Visual disturbances are common with a migraine aura. You may see flashes of light, zigzag lines, stars, or dots of light in your eyes. These symptoms usually go away within 60 minutes.
  • Transient ischemic attacks (TIAs). More commonly referred to as ministrokes, TIAs happen when a blood clot temporarily restricts the flow of blood to your brain. TIAs can cause visual disturbances, including flashes of light in your eyes.
  • Diabetes. Flashes of light or floaters can be a symptom of diabetic retinopathy.
  • Tumors. Tumors in different areas of the eyes or brain can generate flashes when you move your head or neck.
  • Injury. An injury directly to your eye may cause you to see flashes or “stars” due to pressure on the retina.
  • Medications. Some medications may cause flashes of light or floaters in your eyes. This includes:
    • bevacizumab (Avastin)
    • sildenafil (Viagra, Revatio)
Healthline

Retinal detachment is a medical emergency and requires immediate medical attention to prevent vision loss. If you have the following symptoms, get medical help right away:

  • sudden flashes of light, especially when you look to the side
  • partial vision loss or darkened vision
  • blurred vision
  • dizziness
  • other sudden vision-related problems

A TIA can often be a warning sign of a stroke. That’s why it’s important not to ignore the signs. If you notice any of the following symptoms, get medical attention as soon as possible:

  • weakness or numbness on one side of your body
  • slurred speech or difficulty talking or understanding others
  • visual disturbances or visual changes
  • dizziness
  • severe headache

Make an appointment to see an ophthalmologist, optometrist, or your primary doctor if you:

  • have a sudden increase in flashes of light in your eye or eyes
  • notice an increase in the size and number of floaters
  • have a sudden change to your vision
  • have an increase in visual auras with migraine

Your doctor can determine the cause of the light flashes based on the type, duration, and location of these visual disturbances.

Any serious injury to your eye also needs immediate medical attention.

Flashes of light in your eye are typically a symptom of an issue related to your eyes or some other health condition. The treatment will depend on the underlying cause.

When you see your doctor, be sure to go over all the medications you’re currently taking. Some medications can cause vision-related side effects.

In some cases, as with optic neuritis, treating the cause of the inflammation or infection can stop the light flashes.

Tears in the retina or retinal detachment may require surgery.

There’s no treatment for shrinking of the vitreous that normally occurs with age.

Flashes of light can be caused by a wide variety of issues. Some may be related to your eye and some may be a symptom of another type of condition, such as migraine, epilepsy, diabetes, or TIAs.

To stay on top of your eye health, be sure to see your eye doctor for a checkup at least once a year. Regular eye exams can help your doctor determine if there have been any changes to your vision or the health of your eyes.