What are the causes of eye floaters?

Any eye condition in which the clarity of the vitreous humor is altered can produce the symptom of eye floaters. As one gets older, changes normally begin within the vitreous humor. The vitreous gel naturally undergoes some liquefaction, resulting in small pockets of more liquid vitreous lying within the firmer gel. This is called vitreous syneresis. The boundary between each liquid pocket and the gel may be noticeable to the individual as one or more eye floaters. In addition, it is normal for the collagen fibers that are within the vitreous to become thickened and denser with age, resulting in eye floaters. Any person who is over the age of 50 will have these changes within their eyes. However, the degree of eye floaters produced by these typical changes will vary from person to person.

As the vitreous normally ages, the gelatinous structure also begins to shrink within the space that it occupies. This shrinkage often leads to the back surface of the vitreous moving forward within that space. The vitreous is normally attached to the innermost tissue of the eye, the retina, at its posterior aspect at the edges of the optic nerve. As the vitreous shrinks, this attachment to the optic nerve may release, and this former attachment now floats within the eye, causing one or more eye floaters that can sometimes seem very large and circular in shape. In addition, the back surface of the vitreous, now floating within the eye, will also cast shadows onto the retina, producing eye floaters. This shrinkage and pulling away of the back of the vitreous is called a posterior vitreous detachment (PVD) or posterior vitreous separation. It is very different from a retinal detachment. About 50% of 65-year-olds will have a PVD in one or both eyes. A person developing a PVD in one eye is likely to develop a PVD in the other eye within the following 18 months.

In addition to vitreous syneresis and posterior vitreous detachments, both of which are normal occurrences that cause eye floaters with aging, there are a large number of abnormalities in the eyes that may also cause the symptoms of eye floaters. Any cellular material within the vitreous may cause eye floaters. Red blood cells as a result of hemorrhage and white blood cells as a result of inflammation are common types of cellular material causing eye floaters. Hemorrhage into the vitreous may be a result of injury, diabetic retinopathy, a retinal tear through a blood vessel, or eye surgery. Inflammation in the vitreous may be caused by noninfectious uveitis, injury, penetrating or blunt injury to the eye, severe eye infection, or eye surgery.