What are floaters?
You may sometimes see small specks or clouds moving in your field of vision. They are called floaters. You can often see them when looking at a plain background, like a blank wall or blue sky. Floaters are actually tiny clumps of gel or cells inside the vitreous, the clear jelly-like fluid that fills the inside of your eye. While these objects look like they are in front of your eye, they are actually floating inside. What you see are the shadows they cast on the retina, the nerve layer at the back of the eye that senses light and allows you to see. Floaters can have different shapes: little dots, circles, lines, clouds or cobwebs.
Most of the volume of the inside of the eye is filled with a jelly-like material called the ‘vitreous’ (meaning ‘glassy’). The vitreous is tethered to a structure near the front of the eye called the ‘ciliary body’, to the retina along the line of the retinal blood vessels and to the optic nerve head at the back of the eye (figure 1). Early on in life the vitreous is quite solid and rather immobile, but as the eye ages the vitreous develops splits in its structure that fill with fluid. This allows part of the vitreous to become more mobile. In most people, the vitreous eventually separates from its moorings to the optic nerve head and the retina allowing the back surface of the gel to float forwards. This event, called posterior vitreous detachment’ (figure 2) can be preciptitated by trauma, such as a blow to the head or to the eye, or can be a natural accompaniment of ageing.
