A Word from Dr. Thomas Henderson
Even when we are young we can see “floaters” or drifting spots before our eyes. I know I did when I was in 3rd grade, lying on the grass looking at the cloud pictures. I saw lines and squiggles and occasional dots, which were the shadows cast by the supporting structure of the vitreous jelly that fills the back of the eye, in front of the retina. Even as adults we are able to see these “common” floaters under the right circumstances of bright light and a plain background, but mostly our brains have learned how to ignore them.
However, about half of people over age 50, and some people younger, will experience new onset “floaters and flashes”. Risk factors other than age include trauma to the eye and high myopia or near-sightedness. The major event that causes floaters is the separation of vitreous from its normal position on the surface of the retina, which occurs from the wear and tear of moving our eyes many thousands of times a day over many years. The major connection point of the vitreous to the optic nerve head at the back of the eye begins to come forward from its usual position flat on the retina and casts its moving shadow on the retina as the eye moves and stops, and the vitreous sloshes around. The attachment actually is ring-shaped and can sometimes be experienced that way, but usually is noted as a bug or a fly that “isn’t there”. While the vitreous is sloshing, some of the nerve fibers at the lower border of the optic nerve can get tugged on and stimulated, causing a flash of light. Characteristically, this is experienced in the dark or in dim lighting as a quick flash of light in our peripheral vision on one side, moving from above toward the horizon. These flashes go away over several months as the vitreous completely separates from the optic nerve, but the attachment point, the floater, is an intrinsic part of the structure of the eye and will never go away completely. It will gradually drift to a different location and be noticed much less often over time. The combination of age 50 +, a single large floater and a typical light flash is almost always a vitreous separation, but….
Two percent of new vitreous separations will develop a retinal tear, and 1 in 1000 vitreous separations or about 1 in 20 retinal tears will cause a retinal detachment which can lead to a major loss of eyesight and require major eye surgery to repair. When the vitreous sloshes and tears the retina, usually a blood vessel will be crossed, and there will be many new floaters, large blobs, streaks, or blotches, breaking down into many fine dots and tiny donuts as the red cells cast their individual shadows. There might even be a non-typical flash as the sloshing vitreous tugs on the end of the tag of torn retina. If these symptoms occur, it is urgent to be examined quickly to find the tear and have it treated to prevent progression to a retinal detachment. When the retina detaches from the inner wall of the eye, the retina is without its normal blood supply and therefore can’t work properly where it is detached. What people experience is a dark area beginning in the far peripheral, usually inferior vision, which expands over time as more retina falls off. Small detachments are much easier to repair than big detachments, so it is critical to be examined as soon as practical, that evening or the next morning to try to obtain the best result.
The problem is that when the floaters and flashes begin, the person experiencing them can’t look at their own retina to see if it is the usual vitreous separation or the beginnings of a retinal tear. The wise thing to do is to have your ophthalmologist look to see if there is a tear, and to schedule a follow up exam in the future to check if a retinal tear has occurred without symptoms, or an emergency follow-up for a new increase in floaters, maybe with a different flash, or worse, a new dark area in the peripheral vision. Fortunately, most new floaters are just a vitreous separation and one has a chance to make friends with their newest gift from Mother Nature and Father Time. At Eye Clinic of Austin we can examine your eye to determine whether your problem is the common vitreous separation or the uncommon, potentially vision threatening, retinal tear or retinal detachment.
