Washington: Amid a welter of theories explaining why lower eyelids turn baggy with age, University of California researchers have pinpointed how and why fat is primarily responsible.

The study is the first to examine the anatomy of multiple subjects to determine what happens to the lower eyelid with age. It is also the first to measure what happens to the face with age using high-resolution magnetic resonance imaging (MRI).

"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 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 co-author Sean Darcy.

He is a research associate in the division of plastic and reconstructive surgery at the David Geffen School of Medicine at the University. "This orbital septum weakening or herniation-of-fat theory is what most plastic surgeons have been taught.

"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 study looked at MRIs of 40 subjects (17 males and 23 females) between aged between 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.

A report by the American Society of Plastic Surgeons said nearly 2,41,000 Americans underwent eyelid surgery in 2007, making it one of the top four surgical cosmetic procedures performed.

Currently, many plastic surgeons performing procedures to treat baggy eyelids do not remove any fat at all. "Our findings may change the way some plastic surgeons treat baggy eyes," said study co-author Timothy Miller, professor and chief of plastic surgery at the Geffen School.

"Our study showed that a component of a patient's blepharoplasty procedure should almost routinely involve fat excision rather than these procedures," added Miller.

Blepharoplasty refers to surgical rejuvenation of the upper or lower eyelids, or both, depending on the extent of aging or disease. The procedure is usually performed on the lower eyelid because the most common complaint patients have is that their eyes appear tired, puffy or baggy.

The surgeon makes external incisions along the natural skin lines of the eyelid to remove the excess fat and improve the contour of the lower eyelid.

These findings are scheduled for publication in the September issue of the peer-reviewed Journal of Plastic and Reconstructive Surgery. IANS