Featured Research

from universities, journals, and other organizations

Rx For Contact Lenses: Mobility + Lubricity = Comfort And Safety

Date:
May 8, 2001
Source:
American Chemical Society
Summary:
Freedom to move around is a great thing. Just ask a group of researchers who have created a model they hope will lead to better contact lenses. In their eyes, greater lens mobility is needed to improve the safety of extended wear soft lenses.

Freedom to move around is a great thing. Just ask a group of researchers who have created a model they hope will lead to better contact lenses. In their eyes, greater lens mobility is needed to improve the safety of extended wear soft lenses.

Their findings are presented in the July issue of Industrial & Engineering Chemistry Research, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society. The study was led by Clayton Radke, Ph.D., at the University of California, Berkeley.

Researchers and lens manufacturers have known that soft lenses need to be able to move when the eye blinks in order to extend the length of time a lens may be worn safely. Up-and-down lens movement is bothersome, Radke says. Lenses that allow a greater degree of in-and-out, or squeezing, motion work better. The in-and-out motion is less noticeable and permits higher levels of lubricity, helping to flush out impurities that can cause eye problems, according to Radke.

Contact lenses for use up to 30 days without removal were approved by the U.S. Food and Drug Administration in 1981. But increased eye infections and other problems led the FDA to revise its recommendation downward to seven days. Design and material improvements could lengthen that period, Radke said.

Researchers focused on the thin layer of moisture between the lens and the eye known as the "posterior lens tear film." Less than a tenth as thick as a human hair, it can trap bacteria, debris and other irritants, causing problems ranging from bloodshot eyes to conjunctivitis, according to Radke.

He said a lens with greater mobility could result in fewer problems. Soft contact lenses currently in use move very little -- typically less than a tenth of a millimeter per blink, he added.

Radke compared a previously published 23-person clinical experiment involving soft lens wearers with his computer models to gauge the performance of the posterior lens tear film. He found that the tear film liquid under a soft contact lens is typically flushed in about 30 minutes, while bacteria and inflammatory debris take a bit longer. Unfortunately, however, even half an hour may be too long for such material to remain in the eye, he said.

Accordingly, new lens designs are needed, he said. "This study is important to understanding the origin of adverse responses some people have with wearing soft contact lenses and to seeking better lens designs to alleviate them. However, there is always a compromise between increased lens motion and comfort."

For this reason, more study is needed to find the range of motion people can tolerate and to design new lenses that can improve the flushing of eye contaminants, he added.

Of the nearly 25 million Americans who wear contact lenses, approximately 80 percent wear soft lenses, according to the American Optometric Association. That percentage includes daily wear, extended wear and disposable contacts.

Most disposable contacts use the same materials as daily wear soft contact lenses. As a result, they also are vulnerable to irritant problems. Newly introduced silicone hydrogel soft contact lenses provide improved oxygen transfer through the lens to the eye but do not eliminate all adverse responses in extended wear, Radke said. An exception is hard (rigid, gas permeable) lenses, which can move up and down by several millimeters per blink and clear the eye of irritants quicker because of their smaller diameter. Their greater movement and smaller size, however, mean hard contact lenses tend to be more uncomfortable and less popular.

The research cited above was partially funded by Bausch and Lomb and Ciba-Vision Corporation.


Story Source:

The above story is based on materials provided by American Chemical Society. Note: Materials may be edited for content and length.


Cite This Page:

American Chemical Society. "Rx For Contact Lenses: Mobility + Lubricity = Comfort And Safety." ScienceDaily. ScienceDaily, 8 May 2001. <www.sciencedaily.com/releases/2001/05/010508082512.htm>.
American Chemical Society. (2001, May 8). Rx For Contact Lenses: Mobility + Lubricity = Comfort And Safety. ScienceDaily. Retrieved September 16, 2014 from www.sciencedaily.com/releases/2001/05/010508082512.htm
American Chemical Society. "Rx For Contact Lenses: Mobility + Lubricity = Comfort And Safety." ScienceDaily. www.sciencedaily.com/releases/2001/05/010508082512.htm (accessed September 16, 2014).

Share This



More Health & Medicine News

Tuesday, September 16, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

President To Send 3,000 Military Personnel To Fight Ebola

President To Send 3,000 Military Personnel To Fight Ebola

Newsy (Sep. 16, 2014) President Obama is expected to send 3,000 troops to West Africa as part of the effort to contain Ebola's spread. Video provided by Newsy
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com
EU Ministers and Experts Meet to Discuss Ebola Reponse

EU Ministers and Experts Meet to Discuss Ebola Reponse

AFP (Sep. 15, 2014) The European Commission met on Monday to coordinate aid that the EU can offer to African countries affected by the Ebola outbreak. Duration: 00:58 Video provided by AFP
Powered by NewsLook.com
Despite The Risks, Antibiotics Still Overprescribed For Kids

Despite The Risks, Antibiotics Still Overprescribed For Kids

Newsy (Sep. 15, 2014) A new study finds children are prescribed antibiotics twice as often as is necessary. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins