Putting the feet above the head during yoga, handstands or hanging from anti-gravity boots may relieve back problems or tension, but a researcher reports that the upside-down position is dangerous to the eyes.
Dr. Thomas Friberg of the University of Pittsburgh said that a study of 60 subjects showed that all developed increased eye and retinal artery pressure after inverted exercises. Many also experienced temporary visual field losses and eyelid hemorrhages.
Friberg, who presented his data to the recent meeting of the American Academy of Ophthalmology, stressed that the physical changes were not permanent.
“But we don’t know what the outcome would be if a person continued such an activity over a prolonged period of time,” said Friberg, who conducted the studies through the University of Texas Health Science Center in Dallas.
Although he said it was too early to offer firm guidelines, Friberg recommended against staying in the upside-down position for longer than 10 minutes at a time, with two-minute upright breaks between such exercises.
Those who suffer from glaucoma or retinal vascular diseases, which affect the retina, should avoid inverted positions altogether, he cautioned.
“An inverted position may be good for the mind and back, but it causes eye pressure to nearly double--a concern that is especially serious for those who have glaucoma or certain other eye diseases,” he said.
He noted that “more than 1 million Americans have bought the inversion boots, which are hooked to bars so the person can hang upside-down. Also, untold numbers of sports enthusiasts, youngsters conditioning for the Olympics and football players stay in the inverted position for exercise purposes.”
As an extreme example, he cited the case of political prisoner in the Middle East who was hung upside down for 11 hours a day for six months. “Even though the pressure in his eyes is now normal, he has suffered significant damage to his peripheral vision and is legally blind in the right eye,” Friberg said.
It takes up to several minutes for the eye pressure to return to normal after the inverted exercise was completed, he said. “We are uncertain how much the eye can tolerate and for how long without permanent damage.”
“For most healthy people, there is no great danger,” he said, “but we have the concern that some susceptible individuals may suffer damage similar to that caused by glaucoma. At this stage, we don’t know exactly who could be susceptible.”
Glaucoma, the result of increased fluid pressure inside the eye that presses on and damages the optic nerve, can cause blind spots, a loss of peripheral vision and, eventually, blindness.