Photopsia is the presence of perceived flashes of light. It is most commonly associated with posterior vitreous detachment

Posterior vitreous detachment

A posterior vitreous detachment is a condition of the eye in which the vitreous humour separates from the retina.Broadly speaking, the condition is common for older adults and over 75% of those over the age of 65 develop it. Although less common among people in their 40s or 50s, the condition is...

, migraine

Migraine

Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...

 with aura

Aura (symptom)

An aura is a perceptual disturbance experienced by some migraine sufferers before a migraine headache, and the telltale sensation experienced by some people with epilepsy before a seizure. It often manifests as the perception of a strange light, an unpleasant smell or confusing thoughts or...

, migraine aura without headache

Acephalgic migraine

Acephalgic migraine is a neurological syndrome...

, retinal break or detachment

Retinal detachment

Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...

, occipital lobe

Occipital lobe

The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...

 infarction

Infarction

In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...

 and sensory deprivation (ophthalmopathic hallucinations). Vitreous shrinkage or liquifaction, which are the most common causes of photopsia, cause a pull in vitreoretinal attachments, irritating the retina and causing it to discharge electrical impulses. These impulses are interpreted by brain as 'flashes'.

This condition has also been identified as a common initial symptom of Punctate Inner Choroiditis (PIC), a rare retinal autoimmune disease believed to be caused by the immune system mistakenly attacking and destroying the retina.

Photopsia can present as retinal detachment when examined by an optometrist or ophthalmologist. However, it can also be a sign of ocular melanoma

Melanoma

Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...

. This condition is extremely rare (one in 5 million people will be affected, typically fair-skinned, blue-eyed northern Europeans) but if left untreated, will migrate to the liver and shorten life expectancy. Photopsia should be investigated immediately.

Another cause can be nervous spasms.