A medical controversy has erupted over whether suspending oneself upside down in gravity boots is likely to trigger potentially serious eye problems, but the nature of the debate is such that a boot user trying to decide who's right is likely to be left hanging.
This dispute is like many disagreements in modern medicine. There is apparently good evidence supporting both the assertion that using gravity boots may be potentially harmful to the eyes--especially for people with glaucoma, diabetes, high blood pressure and sickle-cell anemia--and the rejoinder that there is no practical reason to believe the danger actually exists.
The situation may, however, leave people who indulge in hanging upside down in the United States--a popular way to treat oneself for backache--somewhat up in the air. That is because reputable researchers disagree on the danger question, as a whole, and because even the two ophthalmologists who believe the boots may cause eye problems--even in normal people--can't say how long is too long to hang.
While the dispute continues, though, makers of the boots note that using them is no longer a mere fad. Duarte-based Gravity Guidance Inc., which pioneered the boots more than a decade ago, claims to have sold more than a million sets. The company says several hundred thousand Americans hang upside down regularly in the belief they can strengthen their backs and decompress their spines.
Dr. Robert Martin II, son of the original developer of gravity boots, asserted that in the 15 years since inversion was first touted as beneficial exercise, there have been no reported cases of eye problems resulting from hanging. Moreover, a Chicago doctor who has written widely about health effects of gravity inversion--and is sympathetic to the cause--said two new studies he has conducted contradict the contention that users may face potential problems that could lead to at least temporary vision impairment.
But in an issue of a prominent medical journal to be published today, researchers at UC San Diego and the University of Texas Health Science Center in Dallas say that based on studies in subjects with glaucoma and normal vision, they recommend that people who have any of a series of eye disorders refrain from hanging upside down "altogether." The study also warns that even people with apparently normal vision should avoid "prolonged periods" of inversion because of the possible risk of eye damage.
At a Loss
The recommendations were made by Drs. Robert Weinreb of UC San Diego and Thomas Friberg of the University of Texas in an article that is being published in the Journal of the American Medical Assn. However, Weinreb and Friberg said they were at a loss to offer guidance to hangers about what "prolonged" means.
Pressed for some definition, Friberg said he would be comfortable with calling any period longer than 35 or 40 minutes "prolonged." It's uncertain what proportion of active hangers turn upside down for longer than that at any one time, however.
Weinreb said neither he nor Friberg, who have also described their research in the influential American Journal of Ophthalmology, had attempted to resolve the time issue and he emphasized that the potential eye problems they described are--for the moment--still best said to be theoretical. But, Weinreb said in a telephone interview, for patients with glaucoma or eye disorders related to diabetes, hypertension or sickle cell anemia, a short period is all that would be necessary to pose a theoretical risk of eye damage. "Thirty minutes would be worse than 10," he said.
Most at issue is hanging's effect on the retina, the innermost and one of the most crucial components of the eye. The retina has often been likened to film in a camera in terms of its critical role in perceiving visual images. It is the part of the eye that brings light rays that enter through the cornea into focus. Its vital blood supply comes from a sophisticated system of vessels.
Friberg emphasized the preliminary nature of the new research, conceding that "we clearly don't have any data that (say) we have people who suffered. We don't have one single individual who did." Both researchers urged caution in interpretation of their findings but urged caution, too, in use of gravity boots--at least until unanswered questions about vision effects can be resolved. The controversy has received added currency by publication this week in Medical World News, a widely read doctors' magazine, of a news account of the research in glaucoma patients.