Eye Floaters (cont.)
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Eye Floaters: Benign Causes
There are two categories of eye floater causes or etiology: benign and pathological. The benign category is by far the most common, while the possibility of a pathologic cause must be evaluated by an eye-care professional, such as your ophthalmologist or optometrist.
Benign etiology: The vitreous gel occupies the bulk of the interior of the eye, containing approximately 5 cc or milliliters of clear jelly. The vitreous gel performs no essential functions other than to occupy a space and to clearly transmit light from the cornea and lens in the front of the eye to the retina in the back of the eye. The gel itself is merely a vestige or non-functioning remnant of embryogenesis, or fetal development of the eye. During the very early stages of embryogenesis, the central cavity of the eye contains blood vessels vital to the normal development of the eye structures. These vessels form during the first trimester of pregnancy. By the end of the second trimester, the vitreous cavity vessels shrink or regress, then disappear completely. The remaining vitreous gel consists of 99% water and 1% protein and resembles clear Jell-O.
The vitreous gel is normally attached to the wall of the eye in two places: the optic nerve head and the front or anterior edge of the retina toward the front of the eye cavity. In many people, these attachments remain in place throughout life, but separation from these vitreous attachments are extremely common. A vitreous separation may occur for any number of reasons, including trauma or injury to the eye, routine ocular surgery, strenuous athletic activity, or simply for no obvious reason at all. Spontaneous vitreous separation from its normal attachment to the optic nerve, in fact, is the most common cause of vitreous or eye floaters.
When the vitreous gel separates from the optic nerve head in the back of the eye, it is termed a vitreous separation, a vitreous detachment, or a posterior vitreous detachment, usually abbreviated PVD. After the posterior attachment separates from the optic nerve, the vitreous, now free to move around within the eye, may bump into or touch the retina, causing flashes or photopsias. Once the separation or detachment process has completed and the entire back face of the gel is removed from the optic nerve attachment, the flashes generally stop. At this juncture, the now collapsed posterior face of the jelly has become somewhat less transparent and it is these aggregations of protein that we call vitreous syneresis or floaters. Occasionally, a small wisp of blood may be seen on the optic nerve or in the vitreous just after the detachment has occurred. These tiny hemorrhages are generally benign and resolve spontaneously. Nevertheless, such a finding should be followed until full resolution by a qualified eye-care professional.
Benign eye floaters occur at all ages. Over half of humanity eventually develops an eye floater, syneresis or PVD. A traumatic birth delivery due to malpresentation, breech presentation, prolonged labor, inadequate birth canal, or forceps delivery may compress the very elastic eyes of the newborn and cause a benign vitreous separation. Benign floaters may occur with even normal vaginal delivery as well.
John D. Sheppard, MD, MMSc
David M. Salib, MD
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