Flashes and Floaters
What are those spots before my eyes?
A very common symptom heard by eye doctors is that a patient sees "spots" before his or her eyes. In fact, people describe a whole assortment of visual phenomena that are collectively referred to as "floaters": small, moving specks, dark blobs, squiggly lines, translucent strands, spider webs, indiscrete smudges, well-defined circular or comma-shaped spots, sparkles, and more. Patients often say that it's like wearing smeared glasses or contact lenses, or having a film over the eyes, except that these "smears" remain even when their glasses or contacts are removed or when they wipe their eyes. Some patients say that something is "in" their eye which, remarkably, is precisely correct.
Floaters occur when the vitreous (vih-tree-us), a gel-like substance that fills about 80 percent of the internal eye, slowly shrinks. As the vitreous shrinks, it becomes somewhat stringy, and the strands can cast tiny shadows on the retina. These are floaters (see figure 1). In most cases, floaters are part of the natural aging process and simply an annoyance. Over time, they tend to settle to the bottom of the eye, becoming less bothersome (like the little, white flakes in a snow globe). They usually settle below the line of sight but do not go away completely. Most people have some floaters but do not notice or learn to ignore them; they become more obvious as they increase in number or size. Floaters become especially apparent when looking at something bright, such as white paper or a blue sky. On rare occasions, floaters can be so dense and numerous that they significantly affect vision. In these cases, a vitrectomy surgery that removes part or all of the vitreous may be considered, but carries significant risks.
Figure 1 – illustration of a floater within the vireous
Floaters are more likely to develop as we age and are more common in people who are very nearsighted, have diabetes, or who have had previous eye surgery. There are other, more serious causes of floaters, including infection, inflammation (uveitis), hemorrhaging, retinal tears, and injury to the eye. People with diabetes tend to have more floaters because high blood glucose alters the chemical composition of the vitreous, causing it to shrink more rapidly. Also, people with diabetes are more likely to have bleeding inside the eyes as a result of diabetic retinopathy, and patients will sometimes visualize individual red blood cells floating around within their vitreous (sort of looks like hundreds of discrete, little peppercorns.)
Sometimes, a section of the vitreous pulls away (detaches) from the retina all at once, rather than gradually, causing many new floaters to appear suddenly. This is called a vitreous detachment, which in most cases is not sight-threatening and requires only close observation, not treatment. However, a sudden increase in floaters, possibly accompanied by light flashes or peripheral (side) vision loss, could indicate a retinal detachment. A retinal detachment occurs when any part of the retina, the eye's light-sensitive tissue, is lifted or pulled from its normal position at the back wall of the eye. Vitreous detachment may be accompanied by quick, often multiple flashes of light (called "photopsia") that occur when the vitreous exerts traction on (tugs on) the retina (the retina doesn't sense pain or pressure – when stimulated, it is only capable of "telling" the brain "I see light!")
Patients with severe diabetic retinopathy (proliferative diabetic retinopathy) are especially at risk for a retinal detachment, as abnormal blood vessels growing into the vitreous are more firmly attached to the retina, pulling it away as the vitreous shrinks (like wall paper being pulled off a wall). If left untreated, a retinal detachment can lead to permanent visual impairment or blindness within a few days or even hours. Those who experience a sudden increase in floaters, flashes of light in peripheral vision, or a loss of peripheral vision should have an eye care professional (optometrist or ophthalmologist) examine their eyes through dilated pupils as soon as possible.
Floaters are very common, extremely annoying, and usually harmless. For people with diabetes, any appearance of or increase in floaters requires immediate evaluation to rule out hemorrhage and retinal detachment. Eye doctors and patients alike can both sleep better knowing that things have been thoroughly checked out and treated, if necessary.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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