Geraldo Magela Vieira of the Institute of Specialized Ophthalmology and UNIPLAC medical school in Brasilia, Brazil, led the study team. After examining 30 healthy men during the performance of various exercises, the scientists found an association between weightlifting and a temporary increase in pressure inside the eye, or intraocular pressure.

It is raised further if breath is held during reps, they noted. Pressure inside the eye tends to rise when air is forced against a closed windpipe. This commonly occurs when a person coughs, vomits, plays a brass wind instrument or engages in heavy weightlifting.

It is this increase in pressure inside the eye that raises the risk of developing glaucoma.

Intraocular pressure rose 90 percent among the men who held their breath on one of four lifts, while it rose 62 percent for those who did not hold their breath at all, the researchers observed.

In glaucoma, the optic nerve that transports visual messages from the eye to the brain is damaged. Early detection is critical to preserving eyesight, as medication can slow down the progress of the disease and even prevent further vision loss. There is currently no cure for glaucoma.

Engaging in aerobic exercise -- jogging, cycling or swimming, for example -- usually is followed by a drop in intraocular pressure. A drop in intraocular pressure also typically occurs after lifting weights or other nonaerobic exercising. It is during the act of heavy weightlifting that intraocular pressure tends to go up.

Although it is a major cause of glaucoma, high intraocular pressure is not the only cause. People with normal eye pressure also have been known to suffer vision loss from glaucoma.