As a person ages, the vitreous gel becomes more liquid. As the eyeball moves, the liquefied vitreous also moves around which can cause the vitreous to pull on the retina. The brain interprets this “pulling” on the retina as flashes of light, thus resulting in a person seeing “flashes”. With time, the vitreous can pull free and separate from the retina and the optic nerve. This is called a posterior vitreous detachment or PVD. A PVD eventually happens in most eyes but rarely causes a problem. The liquefied vitreous can become somewhat condensed and stringy and will form strands. A person can see these strands appearing as spots, small circles or curvy fine threads in the vision. These spots are called “floaters”.
New floaters, especially those in showers and/or accompanied by flashes that continue for 20 minutes or more, should be evaluated to be sure there is no serious retinal problem (such as a retinal tear or detachment). Most disappear on their own or become less noticeable over time.
Retinal tears or holes can be caused when the vitreous pulls too hard on the thin retina, much like trying to remove adhesive tape from tissue paper. These tears/holes can be a potential problem if left untreated. The vitreous gel can enter the hole and lift more of the retina away from the eye wall resulting in a retinal detachment. Vision is lost wherever the retina is detached. Since tears often happen in the peripheral retina, a person may notice a dark shadow or a veil coming form one side, above or below. Left untreated, it is probable that the entire retina will eventually detach resulting in loss of all useful vision in the eye. If the retina tears across a retinal blood vessel, blood may also enter the vitreous (called a vitreous hemorrhage). Vitreous hemorrhages can be small, resulting in floaters similar to a swarm of flies, or much larger causing the person’s vision to become very dark.