October 2009




Determining extended wear contact lens suitability

by Maxine Lipner Senior EyeWorld Contributing Editor


Tracking inflammation levels through tears

Investigators examined extended wear contact lens patients with traditional methods and also tracked progress using their tears Source: Lucy E. Kehinde

As popular as refractive surgery is, there are some who are still hanging on to their extended wear contact lenses. But what effect do extended wear contact lenses really have on the eye when compared with daily wear lenses? That’s just what Lucy E. Kehinde, Ph.D. candidate, School of Optometry, University of Alabama at Birmingham, Birmingham, Ala., recently set out to find.

“The study targeted the effects of 30 days of extended wear and the difference of 30 days of daily wear,” Ms. Kehinde said. “We wanted to find out whether we could see changes in proteins in tears.” Ms. Kehinde was curious to know whether or not there was much of a difference in proteins that are indicators of inflammation.

Assaying tears

For the study, which was recently presented at the May 2009 Association for Research in Vision and Ophthalmology meeting in Fort Lauderdale, Fla., investigators recruited 40 healthy individuals who wore contact lenses on an extended basis. Those included collected their tears with a micro-capillary tube. “They were all trained extensively in non-stimulated tear collection, so it’s very slow,” Ms. Kehinde said. “The tears were then frozen until the day that they were ready to be assayed.”

Prior to the study, patients were asked to stop wearing their lenses for two weeks. They then began wearing the PureVision hydrogel study lenses (Bausch & Lomb, Rochester, N.Y.). Participants were asked to wear the study lens in one eye for 30 days and to use it on a daily basis in the other. Each of the patients came in on the day of extended wear lens insertion and at three time periods thereafter. “I collected tears before patients initially put the lenses in and then after three days, 14 days, and 30 days,” Ms. Kehinde said. Tears were collected by holding the tubes very close to the eye without touching the surface. It was important that these tears be typical ones from the surface of the eye and not those resulting from emotion or physical stimulation since that can affect cytokine levels.

At each point the tears were assayed to look for changes in the proteins. “Twenty-seven cytokines were assayed simultaneously,” Ms. Kehinde said. “One of them showed a significant increase from the day of lens insertion to removal.” The cytokine that increased was an anti-inflammatory one. Ms. Kehinde sees this as likely playing a protective role. “No one had any infections or came in complaining of any discomfort,” she said. “So I would think that having a higher concentration of something that’s known to protect [in these eyes] might make sense.”

Fine-tuning testing

One unexpected result for Ms. Kehinde was the fact that inflammatory cytokine levels did not seem to raise in these extended wear patients. “I was a little surprised that with all the research that has been done with tear cytokines and contact lens wear, I did not see more of a pro-inflammatory effect over 30 days,” Ms. Kehinde said. “Intuitively, we think that after 30 days of leaving something in the eye, some factor would change, whether it’s clinical or on a biomechanical level.” She theorizes that this may be linked to the testing used here. “That could very well be attributed to the assay,” Ms. Kehinde said. “That’s why we’re trying to increase sensitivity and find the most optimal way to measure these cytokines.”

For this reason Ms. Kehinde has repeated the study several times. “The only thing that’s changing each time is the format of the assay that I’m using,” she said. Ultimately, she hopes that the cytokine test can be fine-tuned to provide practitioners with an additional tool for assessing the best candidates for extended wear lens use. “Some of the current tests available are pretty subjective and lack repeatability,” Ms. Kehinde said. “Once the kinks are all worked out, this might eventually be a better way to assess the health of an individual’s eyes or identify suitable candidates for extended lens wear.”

Overall, she sees the study as an important building block. “I wish that I could confidently say now that in healthy individuals, there doesn’t seem to be a major problem with leaving this type of lens in for 30 days, assuming that they engage in proper lens care,” Ms. Kehinde said. “I think that the take-home message is that there is still work to be done and questions to be answered, but this is a major step forward.”

Editors’ note: Ms. Kehinde has no financial interests related to her comments.

Contact information

Kehinde: 203-934-9079, kehinde@uab.edu

Determining extended wear contact lens suitability Determining extended wear contact lens suitability
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