Phospholipid-loaded contact lens may help alleviate dry eye symptoms

In vitro testing showed that DMPC was continually released over a period of 72 hours.

A study has shown that an experimental contact lens loaded with a phospholipid that is slowly released in the eye has the potential to provide relief for the symptoms of dry eye syndrome.

In an in vitro study, which was published in Optometry and Vision Science, daily disposable lenses were loaded with a radiolabeled form of a common phospholipid 1, 2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), found in tears and throughout the body.

William G. Pitt

“DMPC provides extra phospholipids to the eye,” principal investigator William G. Pitt, PhD, the Pope Professor of Chemical Engineering at Brigham Young University, Provo, Utah, told Primary Care Optometry News. “This will help stabilize the tear film in the eye. Especially for people who are deficient in phospholipids in their tears, this will help their tears to be more stable, and they will be able to see better. They won’t have as much eye irritation.”

Dr. Pitt said the DMPC he used is the same chemical as the DMPC found naturally in human tears. “However, for my research, this chemical was radiolabeled so we could measure it,” he said. “In consumer applications, this chemical (DMPC) would not be radiolabeled and will be exactly the same thing as the DMPC in human tears.

“And it is cheaper to get it from soy beans than from human tears, so that is the usual source,” he added.

In the study, silicone hydrogel contact lenses from CIBA Vision (Duluth, Ga.) were immersed in a solution of n-propanol alcohol that contained DMPC.

“Once we immerse the lens in the solution, the n-propanol alcohol will carry the DMPC into the interior of the lens,” he said.

The lenses were soaked between 30 and 120 seconds, then removed from the solution and placed in water for an additional 2 minutes.

“Once the lenses were in water, the n-propanol alcohol diffused out of the lens but left behind the DMPC. In other words, the DMPC that was radioactive was loaded into the lens,” Dr. Pitt said.

To test if the DMPC would indeed release from the treated contact lenses, the investigators placed the lenses in artificial tear fluid (ATF) created in the laboratory.

The ATF was sampled every few hours to measure how much DMPC was released from the lenses and into the ATF.

“The results showed that DMPC came out continually from the lenses, up to 72 hours,” said Dr. Pitt, who also shared these study results at the British Contact Lens Association Conference in Manchester Central, United Kingdom.

After 10 hours, about 0.9 micrograms of DMPC emitted from the lens (comparable to the amount of natural phospholipids excreted in normal tears in 10 hours), whereas after 72 hours there were 2 micrograms, in a lens initially loaded with 33 micrograms of DMPC.

The rate of elution was proportional to the amount of DMPC loaded into the lens. “It was very consistent,” Dr. Pitt said. “Elution was also about five times faster in ATF than in water.”

Moreover, treated lenses retained the same water content, wettability angle, optical clarity and lens modulus as the untreated lens controls, he said.

Dr. Pitt noted that while humidity would not affect the elution rate, “perhaps in a very hot environment (greater than 35° C or 95° F) the elution may occur slightly faster.

Dr. Pitt believes it is possible to load contact lenses on a commercial scale that would look like a normal lens and perhaps be priced at a slight premium.

“I hope this lens comes to fruition because it could be a great benefit for many, many people,” he said.

Primary Care Optometry News Editorial Board member Milton M. Hom, OD, FAAO (Dip CL) commented on Dr. Pitt’s research.

“Contact lens dryness is a common condition; it is a rare day when I’m not dealing with it,” Dr. Hom said. “Supplementation of the lipid layer for dryness works, especially for evaporative dry eye.

“Currently, lipid supplementation is only available in artificial tears,” he continued. “The Achilles heel of artificial tears is residence time. Even the best tears have residence times lasting about an hour. The residence time of the lipid supplementation should be greatly extended if this technology works in real time clinical practice.” – Bob Kronemyer

Reference:

• Pitt WG, Jack DR, Zhao Y, et al. Loading and release of a phospholipid from contact lenses. Optom Vis Sci. 2011;88(4):502-506.

• Milton M. Hom, OD, FAAO (Dip CL), can be reached at 1131 East Alosta Ave., Azusa, CA 91702-2740; (626) 963-7100; eyemage@aaahawk.com.
• William G. Pitt, PhD, can be reached at 350 Clyde Bldg., Brigham Young University, Provo, UT 84602; (801) 422-2589; pitt@byu.edu.
• Disclosures: Dr. Hom has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned. Dr. Pitt has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.