Eye Floaters (cont.)
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 jelly 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 person as one or more
eye floaters. In addition, it 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 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 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 which 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
not the same as a retinal detachment. About 50% of people aged 65 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, 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 uveitis,
injury, infection, or eye surgery.
Next: How common are eye floaters? »
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