Most people in their lifetime will experience floaters. Some start in their teen and most people in the 50’s. 65% of people 65 and older have floaters. They are very bothersome and cause most people to seek an eye exam. Most of the time (about 90%), they are harmless and are a result of the natural aging process in the eye. Sometimes they are a warning sign of bleeding in the eye (most common among Diabetics) or of a retinal tear or detachment. If you are experiencing new floater activity or a change in your floaters you should have a complete eye exam.
Why do they occur?
The most common reason is due to changes in the vitreous which is the clear jelly-like hyaluronic acid which fills the back of the eye. As we age it turns from a solid like jello to a runny jelly and at the same time the attachment to the retina loosens and the back surface of the vitreous pulls off of the retina into the eye. When the vitreous separates from the retina it is called vitreous detachment or separation. Condensed vitreous, debris i.e. blood, Calcium soaps (called “Asteroid Hyalosis”), inflammatory cells, or rarer things can “float” around in the vitreous hence the name floaters. They can result in many descriptions such as, dots, spots, a circle, half moon, insect-like shapes, lines, films or cobwebs. Most of the time they are more bothersome in the first few months and then either disappear, sink down or up out of view or our brains “tune them out”. Most people become accustomed to their floaters and are not bothered by them. In extreme cases they may be always in the line of vision for driving or reading and may need to be surgically removed although this is only in very extreme cases.
What about the 10%?
In some cases when the vitreous pulls away from the retina, it can actually tear the retina. This may result in symptoms of a large, bright flash of light or a stream of floaters that is usually described as red or black ribbons swirling around or unusual or many new floaters. A torn retina is a medical emergency and needs to be treated as soon as possible before the retina detaches. If a retinal detachment occurs one will usually see part of the vision obscured by a curtain-like shape coming from the periphery toward the center. This is a medical emergency and one should seek an ophthalmologist emergently.
What about flashes of light?
Small arc-like momentary flashes of light in the peripheral vision are commonly experienced during vitreous separation. The vitreous pulls on the retina which makes one think they are seeing a light but it is caused by movement of the retina. Sometime the flashes persist for a few months until the vitreous is finished separating. Rarely flashes are associated with a tear in the retina. They should always be evaluated by an eye exam to be sure.
Another cause of flashes is acephalgic (without pain) migraine; other common names are ocular migraine, visual migraine, or optical migraine. This is the visual aura of a classic migraine which begins first with visual phenomena followed by headache. Acephalgic migraine is more common as one ages, although it can occur in youth but usually the migraines transition from severe vascular headaches in later life to visual phenomena without the headaches. Some people have no history of painful headaches but develop the visual phenomena.
These can be varied to include any or all of the following symptoms: holes or blurry places in the vision, heat waves or moving lines, jagged lightening bolt shaped lights that shimmer or move, kaleidoscope like white or colored lights that move. Sometime they are in the form of a crescent and move from the center to one side. The phenomena lasts for minutes to hours (15-20min is most common). They are there with the eyes closed. The cause is vascular spasm in the occipital lobe or visual part of the brain. They are not associated with any permanent problem and one should rest and wait for it to pass. If severe headaches are involved one should seek the care of a neurologist.
Rarely visual phenomena can be symptoms related to the optic nerve or brain and may require ophthalmic or neurological diagnosis and treatment.