What do flashes of light in the eyes mean and how to act

04/11/2025

Have you noticed lights or bright streaks in your vision, especially in the dark or when moving your eyes? These flashes in the eyes, medically known as photopsias or phosphenes, may be harmless or a sign of a more serious eye problem. In this article we explain their causes, when to be concerned and how to act.

What are flashes in the eyes and how are they perceived?

Photopsias are perceptions of light that appear without any external light stimulus. They usually present as:

• Bright dots
• Rays or lines of light
• Sparkling shapes
• Luminous zigzags

These visual phenomena are due to abnormal stimulation of the retina or the optic nerve, without any real light entering the eye.

In most cases these flashes are fleeting, but they may indicate conditions that require urgent ophthalmic assessment.

Most frequent causes of flashes in the eyes

1. Posterior vitreous detachment

With ageing, the vitreous gel inside the eye becomes more liquid, shrinks and partially separates from the retina, and may tug slightly on it, generating brief flashes..

• Common from the age of 50 onwards
• May be accompanied by “floaters”
• In more intense cases, it can cause a retinal tear or retinal detachment

2. Retinal detachment

When the retina separates from the tissue that nourishes it, constant stimulation occurs that generates continuous flashes.

Risk factors

• High myopia
• Ocular trauma
• Previous eye surgery
• Acute vitreous detachment

3. Migraine with aura

Some people experience a visual aura before a migraine, which may include:

• Zigzags or moving bright lines
• Flashes
• Alteration of the visual field

These phenomena usually follow a repetitive pattern and resolve spontaneously after about 10–30 minutes.

4. Pressure or ocular trauma

Blows to the head, pressure on the eyes or sudden changes in intraocular pressure can mechanically stimulate the retina and produce flashes.

Common examples:

• Rubbing the eyes hard
• Sudden postural changes
• Accidental knocks

5. Neurological disorders

Some diseases of the nervous system can alter the way the brain interprets visual signals:

• Epilepsy
• Multiple sclerosis
• Brain tumours

In these cases, the flashes may be accompanied by other symptoms such as double vision, loss of balance or speech disturbance.

When should you see an ophthalmologist?

Although isolated flashes may not be serious, there are symptoms that require urgent attention:

• Sudden increase in “floaters”
• Fixed dark shadow in the visual field
• Persistent flashes without a clear cause
• Partial or total loss of vision
• History of high myopia or previous eye surgery

At Barraquer we evaluate these cases immediately to prevent irreversible complications.

Diagnosis and associated tests

In a specialised ophthalmic consultation the following are performed:

• Dilated fundus examination
• Wide-field retinography to complete an exhaustive study of the retina
• Optical coherence tomography (OCT) to assess the vitreous and the retina with high resolution
• Ocular ultrasound if the fundus is not visible

Flashes in the eyes can be a trivial symptom or an early sign of serious conditions such as retinal detachment. At Barraquer we have advanced technology and an expert retina team to make an accurate diagnosis and offer you the most appropriate treatment.

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