Floaters and Flashing Lights

Medicine for the outdoors is just that – application of the healing arts in outdoor environments, where one must on occasion make do with limited diagnostic capabilities (compared to what is available in a hospital or clinic) and supplies. Often, one must make an educated guess about what might be going on with a victim, medically speaking. Without an x-ray or stethoscope, it may be difficult to confirm the presence or absence of fluid in the lungs or collapse of lung tissue. Without an ophthalmoscope or slit lamp, it is impossible to peer within the eyeballs to determine whether or not there is a problem with the lens, vitreous, or retina. Without a meter to measure the quantity of glucose in the blood, one must rely upon clinical judgment and evaluation of symptoms to estimate whether or not a person is suffering a hypoglycemic episode.

I recently suffered a new (for me) medical problem, as the vision in my right eye was suddenly and painlessly obscured by a tangle of what appeared to be threads and black dots. From my medical training, I knew that these were “floaters,” and was concerned that they might represent a tear in my retina. Fortunately, I was close to the expert care of a skilled eye doctor. At this point, my retina is intact, but I need to be very careful with my activities over the next few weeks until the process of vitreous separation, which I will describe below, subsides.

After I knew for sure what had happened, I thought, what if this had occurred during my recent visit to Mt. Everest base camp, away from sophisticated medical care? What if it happened to someone on a backcountry ski adventure, when exploring in the jungle, or at sea on a diving expedition? If any of these was the case, he or she would have to make due as best possible, worried about what might be wrong and, in the absence of someone trained and properly equipped to complete a full eye exam, unable to truly confirm a diagnosis.

Indeed, this is how most of the world lives. Most people don’t have rapid access to medical professionals, like we do. Furthermore, what I am suffering is actually quite common, and occurs with regularity to persons unable to obtain prompt evaluation. These people must make decisions – do they wait it out and hope for the best, or do they end their travels in order to play it safe and seek an evaluation? This might require expensive and potentially hazardous modes of transportation, which adds yet another layer of risk to the decision making process.

So, using information from an excellent set of patient education instructions provided to me by my ophthalmologist at the Palo Alto Medical Foundation, let’s consider “floaters and flashing lights,” and put it all in the context of what one might do and consider if faced with this problem in an outdoor, remote from medical care, setting.

Floaters are small spots, lines, clouds, cobwebs or veils that move around in your field of vision, especially when you move your eyes. They can be in one or both eyes, but usually show up in one eye at a time. As I can certainly attest, they are easiest to see when you look at the sky or against a plain white background. Floaters are caused by tiny opacities inside the vitreous, which is the gel that fills the inside of the eyes. In childhood and adolescence, the vitreous gel is clear, so that floaters are not seen. In adulthood, floaters can develop when the vitreous gel forms small clumps as part of the aging process. As light passes from the outside of the eye, through the cornea and lens, and then through the vitreous gel before it strikes the retina to record an image, the floaters can cast shadows on the retina. Floaters are annoying, but not dangerous, particularly if they have been present for a long time.

However, the sudden appearance of floaters can signify separation of the vitreous gel from the retina. This occurs because the vitreous gel shrinks as it ages. If it shrinks enough, it begins to peel away from the retina, in what is called a vitreous separation or detachment. It is more common in nearsighted people and in persons who have had cataract surgery or injuries to their eyes or head. When a vitreous separation occurs, the floaters appear suddenly. As the gel peels away from the retina, it tugs on it, which can cause a person to appreciate flashes of light, usually on the outer (ear) side of the eye. These usually last no more than a second, and are caused by the nerves within the retina (which connect to the large optic nerve) being stimulated mechanically by the tug of the vitreous gel. Flashes are difficult to appreciate in daylight, but can be easily seen in the darkness. Moving the head or eyes can cause the flashes. Since flashes mean that the vitreous is pulling on the retina, this is a warning sign, because the traction can cause a retinal tear. If this happens, then an ophthalmologist needs to perform laser surgery as soon as possible in order to prevent a full-blown retinal detachment.

The normal course for a vitreous separation is a 2 to 4 week process in which the separation is completed. This may be punctuated by intermittent addition of new floaters, but usually the burst of opacities is at the beginning of the process. Over time, most of the floaters diminish or disappear, but there may be some residual floaters. During the course of the separation, when a person first notices the floaters, and if a person suddenly develops new floaters, more frequent flashing lights, or a defect in a field of vision (often described as a "dark curtain"), then an ophthalmologist should perform an examination to be certain that there is not a retinal tear or detachment. It is important to avoid sudden eye or head movements for several weeks after the onset of a vitreous separation, in order to decrease the likelihood of developing a retinal tear or detachment.

What does a person do if faced with this situation when distant from the care of an ophthalmologist? The major risk is retinal tear(s) or detachment. If a new vitreous detachment is suspected, then it is wise to begin to head toward civilization in order to undergo a proper examination. However, if it is likely that a retinal detachment has occurred (e.g., there is a "field cut," or a darkened area of vision as if a curtain was being pulled across the field of vision from any direction), then it is prudent to evacuate immediately, including a more expensive mode of transportation if necessary, because treatment for retinal detachment is usually an operation by an opthalmologist, and time is of the essence. A progressive retinal detachment can lead to permanent loss of vision in the affected eye.

In terms of exercise, it is wise to avoid sudden head or eye movements, so no jogging or swimming with rapid head movements, wrestling, significant straining, etc. Until the vitreous separation process is complete, a person should try to turn the head to look in a direction, rather than hold the head in a fixed position and move the eyes. All of this may be difficult in a precarious situation, such as rock climbing or kayaking, but you should just do the best you can given your particular circumstances.

photo courtesy of www.maculacenter.com

Tags: vitreous separation, retinal tear, floaters, wilderness medicine, outdoor medicine, healthline

Labels: eye, eye injury, floaters, retina, retinal detachment, vitreous, vitreous detachment

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A Close Call

Kids will be kids, no matter how much you warn them about potential catastrophes. One came close recently, despite my admonition to be smart and keep his head down. The young man needed to travel a short distance over a remote road and wanted to ride standing in the bed of a pickup truck. The speed was going to be well under 5 miles per hour and there was no chance of a collision, but I was worried about low-hanging branches, a bad pothole or tree root in the pathway, or some other unforeseen hazard. Despite my caution, the boy's father said it was OK for him to ride in the back, which would have been all right 999 times out of 1000.

Except for this time. The poor boy looked away from the direction of travel for a brief moment, and when he turned around to face forward, caught a tree limb across his forehead. He immediately felt severe pain in his eye, and began to shout in distress. It was obvious that he had been struck in the eyeball. When I saw him a few moments later, he was miserable and crying crocodile tears.

I was able to quickly determine that he didn't have a ruptured "globe" (eyeball), and he was begging for relief, so I put a few drops of ophthalmic anesthetic solution into his eye, which made the pain go away quickly. After I pulled his lids back, I was able to achieve fairly good visualization of the surface of his eye. There was one small fleck of tree bark under his upper lid, but otherwise, his eye was free of foreign material. While the surface of his eye remained numb from the anesthetic, I rinsed it carefully with some disinfected water. He was a lucky fellow, because all he had done was to suffer a few small scratches on the white of his eye. If he had not had the great reflexes of youth and been able to duck a bit prior to impact, he easily could have sustained a much worse injury.

What if that had happened? If an eyeball is perforated, there will be a combination of loss of vision (ranging from hazy vision to blindness), pain, excessive tearing, a dilated pupil, and visible blood in the eye. If that is the case, do not attempt to rinse out the wound vigorously; remove obvious dirt and debris without placing any pressure on the eye. Close the eyelid gently and cover the eye with a protective shield. This can be fashioned by cutting gauze pads or soft cloth to the proper size, or by fashioning a doughnut-shaped shield with a cloth, cravat bandage, or shirt. Another good way to keep pressure off the eye is to cut an eye-sized hole in a stack of gauze pads and place the stack over the eye, taping or wrapping it in place. An eye shield can also be improvised by cutting off the bottom 2 in (5 cm) of a paper cup and taping it over the eye. Metal or plastic pre-shaped eye shields can be carried.

Do not exert pressure on the eyeball, because this can increase the damage. Instruct the victim to keep both eyes closed, and start him on oral ciprofloxacin, penicillin, cephalexin, or erythromycin. Seek immediate medical attention.

If the surface of the eye is merely scratched (abraded), then a corneal (clear part of the eye) or conjunctival (membrane over the white part of the eye) abrasion may have occurred. This will be painful because exposure of sensitive nerves to air is sufficient to provoke a significant pain response. If a corneal abrasion is felt to have occurred, the eye can be treated with topical antibiotic solution and the victim provided with sunglasses if the eye(s) has become sensitive to light. It is no longer deemed absolutely necessary to put a patch over an eye that has suffered a corneal abrasion. However, if the pain is relieved significantly by having the eye closed, this can be accomplished by gently taping a patch over the closed eye or by keeping the lids shut with a piece of tape gently applied over the lids. After 24 hours, the patch or tape should be removed to be certain that there is no underlying infection (which should not be patched) and to see if sufficient healing has occurred to allow the victim to tolerate an unpatched eye.

Tags: eye,eye injury,wilderness medicine, outdoor medicine, healthline

Labels: eye, eye injury

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