"A common treatment performed in the past and present is surgical excision of fat to treat a 'herniation of fat' - meaning that the amount of fat in the eye socket does not change but the cover that holds the fat in place, the orbital septum, is weakened or broken and fat slips out," said the study's lead researcher Dr. Sean Darcy, a research associate in the division of plastic and reconstructive surgery at the David Geffen School of Medicine at UCLA and a plastic surgery resident at the University of California, Irvine.

This orbital septum weakening or herniation-of-fat theory is what most plastic surgeons have been taught, Darcy said. "However, our study showed there is actually an increase in fat with age, and it is more likely that the fat increase causes the baggy eyelids rather than a weakened ligament," Darcy said. "There have been no studies to show that the orbital septum weakens."

The researchers looked at detailed MRI images of 40 subjects (17 males and 23 females) between the ages of 12 and 80. The findings showed that the lower eyelid tissue increased with age and that the largest contributor to this size increase was fat increase.

"Our findings may change the way some plastic surgeons treat baggy eyes," said study co-author Dr. Timothy Miller, professor and chief of plastic surgery at the Geffen School. Fat removal should be at least part of the process, the researchers figure.