by Jenna Birch for Yahoo News

And it’s true for both hard and soft contact lenses, according to this new study involving identical twins.

While contact lenses might improve your eyesight without the need for clunky glasses, they might also be having an unintended effect on your appearance. According to a new study published in Aesthetic Surgery Journal, use of contact lenses seemingly leads to eyelid droopiness.

Researchers reviewed photographs of 96 sets of identical twins who met in Twinsburg, Ohio, on a yearly basis from 2008 to 2010, measuring the level of eyelid droopiness (called “ptosis”) in each.

These 39-year-old female identical twins had differing levels of ptosis. The patients were visually identified from a twins database and had individual ptosis measured in each eye. The twin on the left did not wear contact lenses; the twin on the right did wear contact lenses. (Photo: Aesthetic Surgery Journal)

Nine different environmental factors were considered as a potential cause for ptosis, and they were evaluated through an extensive questionnaire and special standardized photography to determine the degree of eyelid droopiness in each twin.

According to the data collected, wearing either hard or soft contact lenses was associated with ptosis. The average difference in eyelid droopiness between twins was 0.5 millimeters. Among twins who didn’t wear contacts, ptosis was around 1.0 millimeter. In twins who wore soft contacts, that number increased to 1.41 millimeters, rising further to 1.84 millimeters for those who sported hard contacts. (Luckily, with the advent of soft lenses, hard lenses have all but disappeared.)

These 65-year-old female identical twins had differing levels of ptosis related to wearing contact lenses. The subject on the left wore soft contact lenses and had less ptosis than her twin; the subject on the right wore hard contact lenses and had more severe ptosis than her twin. (Photo: Aesthetic Surgery Journal)

The researchers also looked for links between ptosis and BMI, smoking, sun exposure, alcohol consumption, work-related stress, and sleep — none of which had a statistically significant impact on eyelid droopiness. The association between contact use and ptosis has been long assumed but never proven, says lead study author Bahman Guyuron, MD, FACS, a facial plastic surgeon based in Cleveland, Ohio.

“Since the identical twins are genetically destined to have similar facial and eyelid features, if there is a difference, it is primarily related to the environmental factors,” Guyuron tells Yahoo Health. “We were able to demonstrate that, of the external factors unrelated to the genes or aging, use of contacts was the only factor that linked to the droopy eyelids.”

Guyuron says the effect they saw was “related to the weakening of the muscles that lift the upper eyelid, and not related to loose or redundant eyelid skin.” And while the mere-fractions-of-a-millimeter difference might seem small, it’s enough to affect vision and appearance.

“Even a minimal droopiness of the eyelids denotes lack of vigor, tiredness, and getting old — often prematurely on the contact lens users,” says Guyuron. And in a culture constantly seeking the fountain of youth, this may matter to some.

Guyuron says that plastic surgeons regularly perform a couple of key procedures for droopiness. According to data from the American Society for Aesthetic Plastic Surgery, 165,714 eyelid procedures and 31,315 brow lifts were performed on patients in 2014.

“Correction of droopy eyelids is one of the simplest and most rewarding surgeries that plastic surgeons do,” says Guyuron. “It is usually a very short procedure, it often requires very minimal recovery, and it makes the patients look younger and more energetic.”

Of course, eyelid droopiness will occur with each passing year anyway — and you can always switch to glasses if you’re concerned about the effects of contact use.