Most of the eye's interior is filled with vitreous. This is a clear, gel-like substance that helps the eye maintain a round shape. There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina (eye's light-sensitive tissue). As we age, the vitreous slowly shrinks, and these fine fibers pull on the retinal surface. Usually the fibers break, allowing the vitreous to separate and shrink away from the retina. This is called a vitreous detachment. In most cases, a vitreous detachment is not sight-threatening. It requires no treatment.
A vitreous detachment is a common condition that usually affects people over age 50. It is even more common after age 80. People who are nearsighted are also at increased risk. Those who have a vitreous detachment in one eye are likely to have one in the other, but it may not happen until years later.
As the vitreous shrinks, it becomes somewhat stringy. These strands can cast tiny shadows on the retina. They are seen as "cobwebs" or specks that seem to float about in your field of vision (floaters). If you try to look at these shadows, they appear to quickly dart out of the way. One symptom of a vitreous detachment is a small, sudden increase in the number of new floaters. This increase in floaters may be accompanied by flashes of light (lightning streaks) in your side (peripheral) vision. In most cases, either you will not notice a vitreous detachment, or you will find it merely annoying due to the increase in floaters. If the vitreous pulls away from the very back of the eye where it is attached to the optic nerve, you may see a small round circle floating within your visual field. This is from the ring of fiber that held the vitreous to the edges of the optic nerve, but has been pulled away.
A vitreous detachment itself does not threaten sight. Occasionally, however, some of the vitreous fibers pull so hard on the retina that they create a hole or tear in the retina. This may lead to a serious condition called a retinal detachment. If the hole occurs at the very back of the eye where all of the light for detailed vision is focused (macula), the ability to see detail clearly may be lost. Both of these conditions are sight-threatening and should be evaluated immediately.
If the vitreous detachment has led to a retinal tear, hole, or a detached retina, early treatment can help prevent loss of vision. However, macular holes may not be treatable. If left untreated, a detached retina can lead to permanent vision loss in the affected eye. Those who experience a sudden increase in floaters or an increase in flashes of light in peripheral vision should have an eye care specialist examine their eyes as soon as possible. If a portion of your visual field in one eye is completely black, like a curtain, you may have had a retinal detachment. The only way to diagnose the cause of the problem is to have a complete dilated eye exam (medicines are put in the eye to make the black circle, the pupil, larger) by an eye specialist.