Post by Admin on Jun 19, 2015 16:40:50 GMT -4
What are eye floaters?
"Eye floaters" are deposits or condensation in the vitreous jelly of the eye. People use the term eye floaters to describe seeing floating spots within their vision when they look around. Eye floaters may be present in only one eye or both eyes.
Why do people notice eye floaters?
The structures in the front of the eye (the cornea and lens) focus rays of light onto the retina. Light focused onto the retina allows one to see. The light going to the retina passes through the vitreous humor, which is a jellylike material that occupies the back two-thirds of the eye. At birth and during childhood years, the vitreous gel is usually totally clear and transparent. Later in life, strands, deposits, or liquid pockets very commonly develop within the vitreous jelly. Each of these strands casts a small shadow onto the surface of the retina, and these shadows may be perceived by the patient as eye floaters. As the eye moves from side to side or up and down, these strands, deposits, or pockets also shift in position within the eye, making the shadows move and appear to float or undulate.
What do eye floaters look like?
People describe eye floaters as spots, straight and curved lines, strings, or "O" or "C"-shaped blobs. Some people see a single floater while others may think they see hundreds. The lines may be thick or thin, and they sometimes appear to be branched. To most people, they appear grey and darker in color than the background. The density of different eye floaters will vary within an individual eye. Eye floaters may be more noticeable under certain lighting conditions and be more apparent when looking at a bright sky. Floaters are rarely seen in situations with reduced illumination.
Like fingerprints, no two people have exactly identical patterns of eye floaters. If a person has eye floaters in both eyes, the pattern of the eye floaters in each eye will be different. In any eye that has eye floaters, that pattern of eye floaters may also change over time.
Eye floaters always appear darker than the background and cannot be seen in darkness or with the eyes closed. This is unlike flashes, which often are seen in the dark and with the eyes closed.
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 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 at its posterior extent 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 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 not the same as 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, 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.
How common are eye floaters?
Eye floaters are extremely common in adults and are a leading symptom that causes people to see an ophthalmologist. Almost everyone has eye floaters by age 70, although some people are much more aware of them than others. It is unusual for children under 16 years of age to notice eye floaters.
What eye diseases are associated with eye floaters?
Abnormal eye floaters are associated with the retinopathy of diabetes, retinal tears, retinal detachment, and large degrees of nearsightedness. They occur more commonly in people who have had injury to the eyes, surgery to remove cataracts, or YAG laser surgery after cataract surgery. Tuberculosis, sarcoidosis, syphilis, toxoplasmosis, and acute retinal necrosis of the eye are other inflammatory diseases that are associated with eye floaters. An unusual ocular condition called asteroid hyalosis is also a cause of eye floaters. Primary or secondary tumors in the eye, including lymphoma and leukemia, are associated with eye floaters, but these are extremely rare.
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