Minor visual disturbances are common and not necessarily cause for alarm. Spots and flecks, known as floaters, in your vision can be annoying but are a normal result of changes in the eye. Some people experience flashing lights, known as scintillations, in their vision with no ill effects. If you suddenly begin to see frequent flashing or pulsating lights, or if any visual disturbances are accompanied by pain, ask an eye doctor for advice.
Migraine
Visual disturbances, including flashing lights and lines, often occur before a migraine headache. Migraines are painful and may last up to 72 hours, but they are not dangerous. Ask a doctor to investigate any new severe headaches to rule out other causes. Migraines may also affect your vision. Ocular migraines may cause a blind spot with scintillations or a flashing zigzag line. They are painless and do not need treatment, according to the website All About Vision.
Eye Damage
Scintillations may accompany symptoms of damage to the retina at the back of the eye. Marilyn Haddrill at All About Vision observes that sudden presence of spots, floaters and flashes of light may be warning signs of a detached retina. She quotes a study reported in late 2009 in the "Journal of the American Medical Association," which says that one in seven people with these symptoms will have a retinal tear or detachment. Spots and floaters may also be signs that the vitreous humor, the gel-like substance inside your eye, is liquifying and detaching from the retina. This may happen spontaneously with aging.
Stroke Warning
Scintillations combined with temporary loss of vision in one eye may be a sign of a carotid artery dissection. This is a weakening of the wall of the vessel taking blood to your brain. It may lead to a stroke if not treated immediately. If you have a family history of early-onset strokes, or if you have recently sustained a head injury, this possibility is more likely.
Medication
Flashing lights in your vision may sometimes be a side effect of medication. Digitalis and other heart drugs occasionally cause this symptom. If you are taking a new medication, tell your doctor about changes or new disturbances in your vision.
Precautions
If you have your eyes and general health checked regularly, most visual disturbances will be completely harmless. However, since they may occasionally signal an underlying condition requiring treatment, ask a doctor about any sudden onset of seeing flashing lights. Be particularly vigilant after any head injury or surgery. Never drive when your vision is disturbed.
