The retina is the thin, light-sensitive nerve fiber layer lining the back of the eye that receives light and visual images through the rest of the eye. It is held up next to the back wall of the eye by the vitreous body, also known as the vitreous humour, a stiff, gelatinous substance. The vitreous is actually attached to the retina in several places, most notably around the periphery of the retina, just in front of the midline equator of the eye, and around the optic nerve head.
Like most tissues in the body, the retina and the vitreous change with aging; the vitreous becomes more liquid-like and may move around inside the eye more and the retina itself becomes thinner and even more susceptible to damage.
Atrophic retinal holes are thought to be caused by these aging changes in both the retina and the vitreous humour. The retina can begin to disintegrate over time, usually out in the peripheral area of the eye, and as the vitreous becomes more mobile, it may bump up against the retina and even become loose from its normal attachment sites.
As the retina thins and forms holes in the periphery, it causes loss of vision, but because these holes are usually small and out in the far peripheral visual field, they are not usually even noticed or require treatment. Unfortunately, this condition may occur along with lattice degeneration, a rather common condition that also causes retinal thinning in the peripheral retina. Patients who have either or both of these conditions are usually asymptomatic and are usually only first diagnosed in a routine pupil dilation done during a regular eye examination.
As the vitreous becomes more liquid-like, it shrinks slightly and may tug on the retina at those sites where it is attached, most notably in a belt-like area around the eye just in front of the equator. This is known as a vitreous detachment, which is quite common and should not be confused with a retinal detachment, which is much more rare and much more serious.
A person with a vitreous detachment may experience small flashes of light from the corner of the eye and an increase in the number of noticeable floaters; the flashes happen because the retinal tissue responds to any stimulus by sending signals to the brain, which interprets any such signals from the retina as light.
Sometimes, patients will develop a vitreous detachment from around the head of the optic nerve in the very back of the eye; these patients will probably also notice some light flashes, this time more towards the center of vision, and begin to notice a ring-shaped or arc-shaped floater, which is caused by small pieces of the retinal tissue coming away with the vitreous. This in itself is not particularly dangerous or uncommon, and requires no treatment, except to see an eyecare practitioner to rule out more serious problems.
Those patients who have other risk factors for retinal detachment (high myopia, or nearsightedness, lattice degeneration, family history) should know the symptoms of it, which include a sudden onset of flashes and/or floaters in the vision, a loss of vision, usually in the lower part of the visual field, or even what looks like a curtain across their vision. These are signs of a possible retinal detachment, which is a sight-threatening emergency. See your eyecare practitioner right away if these occur.
Chances are that the symptoms experienced are from a vitreous detachment or atrophic retinal holes, but for those whose condition progresses to retinal detachment, treatment may include surgery to re-attach the retina and hold it in place, or laser photocoagulation, which is used to surround a retinal hole or detached area with small, pinpoint scars to seal it to the back of the eye again.
Unfortunately, there is very little that one can do on a preventive basis to avoid atrophic retinal holes or lattice degeneration, but regular eye examinations and immediate evaluation of any unusual visual symptoms are the best way to avoid further damage.