New contact lenses prevent contact lens-induced dry eye

Contact lenses to treat dry eye syndrome.

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The contact lens (CL) industry has dramatically improved CL-wearing experiences. However, many CL wearers continue to experience ocular dryness, known as contact lens-induced dry eye (CLIDE), stemming from the reduction in tear volume, tear film instability, and increased tear osmolarity followed by inflammation and resulting in ocular discomfort and visual disturbances.

Rewetting drops, gels, lubricants, more frequent lens replacement, or modifications to the lens material are currently available treatments for this issue. Treatments for the eyelids include warm compresses and eyelid massages. 

In more extreme circumstances, punctum plugs—devices that are put into tear ducts to prevent drainage—as well as manual stimulation of the tear glands may be used. However, the effectiveness of these treatments varies, as do the risks associated with medication buildup in the body and the unintuitive procedures that increase patient noncompliance.

A contact lens prototype specifically made to avoid contact lens-induced dry eye (CLIDE) has been created by a team from the Terasaki Institute for Biomedical Innovation (TIBI). By encouraging tear flow due to regular eye blinking, the lens helps treat this problem.

TIBI contact lens
The prototype TIBI contact lens. Credit: Terasaki Institute

There have also been previous attempts to use contact lenses in treating dry eye syndrome, such as graphene-coated lenses designed to minimize moisture loss and self-moisturizing lenses stimulated with metallic electrodes. But these methods are costly and impractical and may compromise patient safety and comfort.

In this new approach, the team used a contact lens design that includes microchannels to facilitate tear flow movement and flow so that dry eye can be avoided. No external devices are required because the pressure can be applied by natural eye blinking.

The team used a lens mold made of a silicone polymer mixture for fabrication. This allowed for easy removal of the lens cast on it by gently bending the mold. 

Earlier techniques required removing the lens for twelve hours in hot water. The method produced lenses that could be thirty times smaller than previous lenses and high-quality, smooth microchannels. Reservoirs for the input and outflow of liquids were constructed at the ends of each microchannel using a special device.

The team also used innovative methods to insert the microchannels in a sandwich-like assembly under a capping lens layer. The lenses first curled due to the dehydration that occurred while preparing the two lens surfaces for stronger bonding. The two lenses were attached to holders using water-soluble glue to overcome this issue. This not only helped the lenses connect more uniformly but also served to shield them from harm.

The team carefully examined the stability and leaking of their encapsulated microchannel lenses before putting them through a series of tests with a tool they developed to mimic an eyelid blinking. This mechanism was put into the lens prototype to pressurize the lens and encourage tear production artificially.

After various experiments, a configuration that proved effective was microchannels with square cross-sections arrayed in a novel circular pattern on the lens surface; this was compatible with the function and curvature of the lens and allowed for optimum liquid flow.

Ali Khademhosseini, TIBI’s Director and CEO, said“The inventive methods that our team has employed bring a potential solution for millions of people. It is the hope that we may extend our efforts to bring this solution to fruition.”

Journal Reference:

  1. Yangzhi ZHu et al. A Microfluidic Contact Lens to Address Contact Lens-Induced Dry Eye. Small. DOI: 10.1002/smll.202207017 
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