Study co-author Dr. Timothy Miller, chief of plastic surgery at the Geffen School at the University of California, Los Angeles, said currently, many plastic surgeons performing procedures to treat baggy eyelids do not remove any fat at all.

Surgeons reposition the fat or conduct more invasive tightening of the muscle that surrounds the eye, or they tighten the actual ligament that holds the eyeball in place -- these procedures are performed despite there being no data indicating that these structures change with age, Miller said.

"Our findings may change the way some plastic surgeons treat baggy eyes," Miller says in a statement.

High-resolution magnetic resonance imaging of 40 subjects -- 17 males and 23 females -- between the ages of 12 and 80 showed the lower eyelid tissue increased with age and that the largest contributor to this size increase was fat increase.

The researchers say the study, published in the September issue of the Journal of Plastic and Reconstructive Surgery, is the first to examine the anatomy of multiple subjects to determine what happens to the lower eyelid with age and measure what happens to the face with age using MRI.