There are many different kinds of retinal detachment disorders. The most serious retinal problems that require surgery are caused by difficulties with the vitreous. This clear gel-like substance fills the central cavity of the eye and is attached to the retina. It is most strongly attached to the retina at the optic nerve, macular area, and in a belt-like circle at the front part of the eye called the vitreous base.
As a person ages, the thick vitreous gel becomes less like a gel and more like fluid, and small pockets of fluid form within the gel of the vitreous. As the eyeball moves, the liquefied vitreous moves around inside the vitreous cavity. Because of the movement of this fluid, the vitreous begins to pull on the retina, and with time, the vitreous can pull free and can separate from the retina and from the optic nerve in the back, or the posterior, part of the eye. This is called a posterior vitreous detachment (PVD). This type of detachment usually eventually happens in most people, and only infrequently causes a problem. By age seventy, 70% of patients have had a PVD, and by age one hundred, nearly everyone has it.
When a person develops a posterior vitreous detachment, flashes of light or large spots in the vision may occur. The flashes of light are caused by tugging of the vitreous where it attached to the retina. As the vitreous liquefies and pulls away from the retina, the vitreous becomes somewhat more condensed and stringy, forming strands. These strands and strings can be seen as spots, small circles, or irregular fine threads in your vision, and are called floaters. Vitreous changes are most commonly caused by aging, but can also be caused by previous inflammation in the eye, nearsightedness, trauma, or previous surgery. If you have floaters, you should be examined to be certain there is no other serious retinal problem such as a retinal tear or detachment.
There are many areas where the vitreous is very strongly attached to the retina. If the vitreous pulls away from the retina in an area where the retina is weak, it may cause a retinal tear. One condition which weakens the retina is called lattice degeneration, a rare inherited trait. When lattice degeneration is present, it indicates that the retina is thin and may be more susceptible to a tear of the retina than in an area without lattice degeneration.
If the vitreous is firmly attached to an area of the retina or if the retina is weak, as the vitreous pulls away, it can tear the retina. If the tear occurs across a blood vessel, there will be bleeding into the vitreous. This is called a vitreous hemorrhage. When there is a little bleeding, red blood cells floating and moving in the vitreous cavity create the sensation of walking through a swarm of flies. If more bleeding occurs in the vitreous, it looks like a spider web or a swirling mass of black or red lines. With a lot of bleeding, vision may reduce significantly or even become very dark. When a retinal tear occurs, it is a potentially serious problem. If a vitreous hemorrhage also occurs, it is even more serious.
The retina can tear immediately following a posterior vitreous detachment, or weeks later. If a tear has not developed within eight weeks after a posterior vitreous detachment, it is much less likely that the retina will do so. Anyone who develops a sudden onset of new floaters or flashing lights of any kind should have a complete retinal evaluation. These symptoms may indicate that a retinal tear has occurred. A retinal tear can result in a retinal detachment.