Why do I see flashes?

11/10/2024

Flashes in the eyes, also known as phosphenes or photopsia, are visual perceptions of light that are not actually present in the environment. They can appear as bright spots, streaks, or shapes in the visual field, either peripheral or central. They occur due to abnormal stimulation of the retina or optic nerve, which can be caused by various factors depending on the source of the stimulus.

• Vitreous detachment: With age, the vitreous gel that fills the inside of the eye begins to shrink and become more liquid. As it separates from the retina, it can pull on it slightly, causing mechanical stimulation of the retinal cells and flashes of light. If the vitreous detachment is severe, it can cause a retinal tear or detachment.
• Retinal detachment: If the retina becomes detached from the underlying tissue that nourishes it, constant mechanical stimulation can generate flashes of light. This can be caused by eye trauma, severe myopia, or, as mentioned above, vitreous detachment.
• Migraine with aura: Some people who suffer from migraines experience visual auras, which may include flashes, bright zigzags, or different patterns in the visual field.
• Pressure on the eye or optic nerve: Rubbing the eyes, suffering a blow to the head, or a sudden change in intraocular pressure can stimulate cells in the retina or optic nerve, causing the perception of flashes.
• Neurological problems: Some neurological disorders, such as brain tumors, epilepsy, or multiple sclerosis, can affect the way the brain processes visual information and lead to seeing flashes or lights.

We can summarize that flashes in the eyes occur when something stimulates the cells of the retina or optic nerve abnormally, either due to mechanical or neurological causes. In many cases, flashes are usually harmless. However, if they are accompanied by a sudden loss of vision, an increase in "floaters," or if they are persistent and not related to known migraines, it is important to consult an ophthalmologist immediately to rule out serious conditions and obtain appropriate treatment.

Dr. Mª José Capella Elizalde, ophthalmologist at the Barraquer Ophthalmology Centre