There are several types of flashing lights can be seen by patients as a result of different medical conditions. Some of these symptoms come from the eye and others come from the visual centers in the brain.
Flashing lights that come from pulling forces on the retina are usually very brief flashes of light that occur in the peripheral, or side vision. They usually last less than a second, like a bolt of lightning. They can sometimes be precipitated by moving the eyes and are usually most apparent in a dark environment, although they can even be seen in the light sometimes. This type of flashing light is usually due to something stimulating the retina, which is then causing the retina to send neural signals to the brain, which are perceived as flashes of light.
Causes of Photopsias
Vitreous detachment, also known as a posterior vitreous detachment. In most people this is a normal aging change, although it can happen in younger patients, especially if they are near sighted. It most commonly occurs after the age of 50. The vitreous gel is a clear, solid ball of gel in a newborn. This is not a watery gel like common gelatin. It actually has a fibrous structure that is transparent and is very firmly attached to the retina at birth. The retina lines the inside wall of the eye. As we age the gel tends to liquify and shrink, eventually pealing away from the inside wall of the eye. When it does this it can pull on the retina, stimulating the retinal nerve cells and causing a brief flash of light to be seen. These flashes usually go away within a few weeks, but can occasionally last for months or longer, and rarely even years. There is no treatment needed for these symptoms since they usually subside on their own. They can result in floating particles in the eye (see “Floaters). Occasionally the gel can pull a hole in a retinal blood vessel causing bleeding in the eye. If a retinal tear or detachment does not result, the body will frequently clear the blood out of the eye without treatment. If this doesn’t happen, the blood can be removed with surgery. The good news is that blood in the eye takes a long time to damage the eye permanently, usually more than a year, by which time most patients have seen an eye doctor.
Retinal tears and detachments. A less common cause of photopsias is a retinal tear or detachment. This occurs when the vitreous gel is abnormally adherent to the retina. In this case when the gel pulls on the retina, it stimulates the retina to send signals to the brain, but it doesn’t release, as in a vitreous detachment. The pulling force from the detaching gel tears a hole in the retina. This is usually accompanied by multiple small floaters. It can also result in bleeding into the eye (see “vitreous hemorrhage”). If the retinal tear is not treated, there is a high risk that it will progress to a retinal detachment. This will often result in a blind spot developing in the peripheral (side) vision. This can happen anywhere in the peripheral vision. The area usually starts small and gets larger, heading toward the center of vision. It isn’t a blurred area, but a true blind spot. The patient can’t see through it. Sometimes the area is dark and often has the shape of a half moon or crescent.
Photopsias can be due to other disease processes. Just about any disease that irritates the retina can have flashing lights as a symptom. Swelling of the center of the retina (macular edema) can sometimes cause a “pinwheel” type of flashing lights in the center of the vision. This is most commonly associated with “wet” age related macular degeneration. Patients can sometimes see flashing lights after the retina is surgically reattached as the retinal cells recover. The list of other causes is long including intraocular inflammation (uveitis), poor circulation to the visual center of the brain, high or low blood sugar in diabetics, severe coughing, fluid under the retina (central serous chorioretinopathy), hereditary retinal degenerations (retinitis pigmentosa), and a multitude of adverse reactions to drugs.
Zig-zag flashing lights. This is often a migraine prodrome or aura. Patients can experience what is known as a scintillating scotoma. This is very different from the flashing lights seen in retinal conditions. It is usually described as zig-zag flashing lights or a saw tooth pattern followed by a blind spot that can enlarge over several minutes. Some patients describe sparks or flares. Some say it is like looking through a screen door. It may appear to be coming from one or both eyes, It usually lasts for several minutes to an hour. In younger patients it can be followed by a migraine headache, but in people older than 40 and in post-menopausal women the symptoms may subside without a headache. Some patients have a personal history or family member with migraine headaches, but occasionally we see patients that have never had migraine headaches in the past and the symptoms resolve with out a headache. These symptoms may occur in clusters or they may be very infrequent, occurring only every few months or years. They rarely need treatment.
Flashing lights can be worrisome and even frightening symptoms. The cause of these symptoms can’t be diagnosed without an examination. We recommend a dilated examination by an ophthalmologist for new onset flashing lights.