When to Consult a Doctor
However, if they are new, become more numerous over time, have a reddish color to them, or are associated with flashing lights, then they may represent a serious problem that should prompt a call to your ophthalmologist.
Retinal Tears and Detachment
Retinal tears or detachments often cause flashing lights and new floaters. The flashing lights are usually seen in an arc at the edge of the visual field and are caused by the vitreous jelly pulling on the retina. If you have these symptoms, you should call your ophthalmologist right away.
A retinal detachment is painless if it occurs spontaneously, or may be associated with eye pain if caused by getting hit in the eye. As a retinal detachment progresses, it looks like a black curtain coming across your vision, usually over the course of hours or days. It usually starts at the edge of the visual field and moves toward the center.
Some people have migraines that cause flashing lights in the center of the visual field followed within about 30 minutes by a severe headache on one side of the head. This is different from the retinal detachment symptoms.
Sometimes bleeding into the vitreous can cause floaters, which may have a reddish appearance. This is most likely to occur in diabetics who have new, abnormal blood vessels growing on the surface of the retina and into the vitreous. These vessels can leak and bleed, sometimes filling the vitreous with blood or blood spots. If you have these symptoms, you should call your ophthalmologist right away.
Severe inflammation in the eye can cause white blood cells to enter the vitreous, and this can look like floaters. These are more common in patients with autoimmune diseases like lupus or sarcoid.
Very rare disease-causing floaters can occur with ocular lymphoma, where cancerous white blood cells grow in the vitreous. Even rarer is retinoblastoma, a form of cancer seen in babies that can cause white vitreous floaters that make the pupil look white in photographs (normally it would look red).
In summary, eye floaters are caused by thickened clumps of vitreous jelly. Many people have vitreous floaters, which are usually not concerning if they are stable and not associated with any other symptoms. However, if they are new, increasing in number, or associated with flashing lights or eye pain, then call your ophthalmologist right away.