Seeing Stars in Vision Explained
Did you ever close your eyes and push on them with your fingers as a child to see waves and patterns of color float across your eyelids? Perhaps more commonly for adults, have you ever stood up suddenly from reclining or laying down and seen spots swimming across your vision? Or maybe you suffer from migraines that begin as flashes and spots of light crossing the visual field. Hopefully you have never been knocked on the head hard enough to cause flashes of light, but that is another way that you may see strange spots that don’t actually exist. This phenomenon of “seeing stars in vision” is called a “phosphene,” and is the experience of seeing light when no light is actually entering the eye.
How can I see light where no light is present?
There are several ways that the eye can see light where no light is present. In order for us to see, our retina must be stimulated by light waves, which our brain then translates into an image. But the retina can also be stimulated physically, electrically, and magnetically. Most phosphenes that people experience are physically induced. When you rub your eyes or close them and put pressure on them, you activate cells in the retina, which the brain is required to interpret as a visual signal. Thus, you see waves of color and patterns of black and white. Since there are no light waves actually entering the eye, the brain cannot create a picture (like a floating meatball sandwich), so you simply see patterns, colors and spots. Other physically induced phosphenes can include seeing spots when you sneeze – sneezing puts a lot of pressure on the eyes and on the light-receiving cells in the eyes.
Fluctuation in blood pressure
When you have been in a reclined position for some time and then stand up, you may experience a drop in blood pressure. The eye has a very high metabolism, so that drop in blood pressure results in a loss of oxygen to the retina, which can cause it to misfire signals to the brain. On an opposite note, if you are experiencing seeing stars in vision while pregnant without having just stood up, this can be a signal of pre-eclampsia, a serious condition involving high blood pressure, and you should see your care provider immediately about this concern. Another physically induced phosphene is caused by migraines. Migraines are spasms of blood vessels in the brain, and flashes and spots that come on before a migraine are caused by spasms of blood vessels in the retina.
A bump on the head
Finally, seeing spots when you have been hit in the head is not necessarily caused by physical stimulation to the retina, but often because the part of the brain that processes signals from the retina and produces images, known as the occipital lobe, gets bumped. This can irritate the visual cortex, located inside the occipital lobe, and in the same way that physical stimulation of the retina produces spots, physically stimulates the cells in the visual cortex to produce spots and flashes.
Seeing stars is generally not a concern for eye health
Usually, seeing spots or flashes of light is not a concern and can be explained by one of the reasons above. However, if you are experiencing a sudden increase of flashes or spots, it can be a sign of a detached retina, which is a medical emergency because it can lead to permanent blindness within a matter of hours. Contact your eye doctor immediately, and if you cannot reach the eye doctor, go to the emergency room.