The vitreous is a gel, made mostly of collagen fibers, that fills the part of the eye behind the lens and in front of the retina. Unless there’s a problem, the vitreous is transparent and lets light pass through it, on to the retina (the part of the eye that converts light into information for the brain that enables you to see).
As you age, the gel starts to become less homogenous – collagen fibers tend to clump together. These look like shadows or ‘floaters’ under certain light conditions; patients often describe them as ‘patches’, ‘strands’ and even ‘small flies’.
The vitreous is contained inside a membrane – much like air is held inside a balloon. The vitreous ‘balloon’ is inflated inside the eye, and it’s anchored to various points inside the eye.
Floaters are usually harmless, and are more common in people aged over 50 years or in those with myopia (short sightedness). Unless lots appear at once, or they are associated with flashes of light (see retinal tear and retinal detachment), they aren’t dangerous, but they can be bothersome.
Floaters can be surgically removed by surgery in which the vitreous is removed entirely and replaced with a clear saline solution (a procedure called vitrectomy), but this increases the risk of developing cataracts early. Therefore, the operation is only performed if the floaters are massive and very central, and strongly interfere with reading or writing.
As people age – and this will happen to everyone, eventually – the vitreous starts to shrink (like a balloon) over a period of a few days to several weeks. This usually happens when people are aged 40–60 years old, although in the case of myopes (short-sighted people), this process can occur much earlier. Normally, this (completely natural part of aging) has no adverse effect on the eye, but during this period, there’s a risk that the shrinking vitreous might pull on the retina, and create a retinal tear. If the tear permits fluid to enter the retina, this can go on to cause what’s called a retinal detachment – which is an ophthalmic emergency needing immediate treatment. Just before a retinal detachment takes place, people tend to see flashing lights in the affected eye, and often see an abundance of floaters.
As long as you see flashing lights, the posterior vitreal detachment is still ongoing. While this is happening, we will examine your retina at regular intervals to be sure there is no retinal tear.
In between our ophthalmological inspections, you should be vigilant to changes in your vision in the affected eye. Proceed as follows:
If you see flashing lights in your right eye, close the other (left) eye. Now look at an object and move your hands to the outstretched arms on the outside of your field of vision. Do you see your fingers out of the corner of your eye? Repeat the test with the other eye. The fields of vision of the individual eyes should be similar.
Retinal tear explained
Remember: vitreal detachment is a natural process. Everybody experiences it in the course of their life and with only a few eyes go on to have a retinal tear. However, if this does occur, we can perform a laser treatment and “weld” the crack. But these tests are an important precautionary measure.