The eye is filled with a clear jelly called the vitreous gel. The vitreous gel inflates the back part of the eye in the way that water inflates a water balloon. As we age, the vitreous gel begins to dissolve into a more watery form. Once enough of the vitreous gel has dissolved – usually when we are in our late 50’s or early 60’s – the gel pulls free of its attachments to the back of the eye. This sudden and often dramatic event – called a posterior vitreous detachment – often causes a number of symptoms that can be alarming.
One common symptom of a posterior vitreous detachment is the appearance of floaters. Floaters are exactly what they sound like – tiny bits of debris that appear when the vitreous gel separated from the back of the eye. These bits of cloudy debris float in the liquefied vitreous like snow in a snow globe. If you have a single small floater, you may have the sensation that a bug is flying in your face. Often in eyes with posterior vitreous detachments, the floaters are bigger and somewhat stringy, and you may describe it as a spider web or cobweb in your vision. Typically, these floaters will move around in your vision, especially when you move your eyes around. Floaters usually do not stay in exactly the same spot in your vision.
Another common symptom of a posterior vitreous detachment is seeing flashing lights in the very periphery of your vision. As the vitreous gel pulls loose from the back of the eye, it tugs on the wallpaper lining the back of the eye. This wallpaper is called the retina. The retina is a thin layer and is like the film of a camera—it is the light-sensing part of the eye. When the retina is tugged on, it generates the sensation of flashing lights in the periphery of your vision.
Floaters are often annoying but not usually a threat to vision. But flashing lights can be a more worrisome sign. Sometimes when the vitreous tugs on the retina as it is pulling loose, it can pull so hard that it makes small rips or tears in the retina. The liquefied vitreous can then pass through the hole and cause the retina to come loose from the back of the eye as well. This is called a retinal detachment. If you have a retinal detachment, you may notice sections of your vision disappearing, as if a curtain or veil is covering parts of your vision. A retinal detachment is an emergency and often requires surgery to repair.
If you have the sudden onset of new floaters in your vision and/or flashing lights in the periphery of your vision, call your eye doctor immediately to arrange a prompt examination. During this examination, your pupils will be dilated to examine your retina to make sure there is no retinal detachment. While they are uncommon, retinal detachments can cause vision loss, and repairing them quickly is the best way to save your vision.