Advancing beyond gauze and pirate eye patches to protect injured eyes

USC scientists and engineers develop an on-the-spot, temperature-sensitive gel that could seal eye injuries on the battlefield. The gel has only been tested on rabbits. Human clinical trials could begin in 2019.

When traumatic eye injury on the battlefield or in civilian life, any delay in treatment may lead to permanent vision loss. With medical facilities potentially far away and no existing tools to prevent deterioration, medics are in a high-stakes race against the clock.

The gel seals eye injuries. When the patient is ready for surgery to repair the injury, the seal can be removed by adding cool water, the researchers said.

* The gel seals the damaged eyeball like using bathroom caulking so it simple to use
* it takes about 5 minutes to apply
* it directly seals the eyeball

Currently covering eye injury and using some gauze

More about the new gel

“If you look at historical data over the last several decades, the rate of war-related ocular [eye] injuries has steadily increased from a fraction of a percent to as high as 10 to 15 percent,” said John Whalen. He is an assistant professor of research in the department of ophthalmology at the University of Southern California.

The battlefield isn’t the only place the gel could be used.

“First responders at a mass casualty incident could deploy the hydrogel while patients wait for their injuries to be completely repaired by an ocular surgeon in appropriate microsurgical facilities,” Whalen noted.

“It could also be useful in emergency rooms in rural areas where there isn’t an eye center with such capabilities nearby,” he added. “It may even have potential for temporarily treating gunshot wounds.

A custom fit
The material the group was working with for retinal implants was a hydrogel called PNIPAM, poly(N-isopropylacrylamide), which had a unique attribute that made it a natural fit for this application: When cooled, the hydrogel became a liquid for easy application, and when heated, it became a viscous semi-solid with strong adhesion. All that was needed was some tailoring.

“Since the initial hydrogel’s transition temperature was very close to the temperature of the human eye, we had to modify its properties to ensure that it would form a solid seal as soon as the gel was applied to the eye by a soldier or medic,” said lead author Niki Bayat, a doctoral candidate in the Mork Family Department of Chemical Engineering and Materials Science at USC Viterbi. “Providing a perfect, yet reversible seal, the smart hydrogel shows promise for the next generation of tissue adhesives.”

When an ophthalmologist is ready to repair the eye, the hydrogel can be extracted by applying cool water and converting it back to a less adhesive state.

Special delivery
The research team also developed a special syringe for the hydrogel that would be easy to use on the front lines and capable of quickly cooling the hydrogel before application. The syringe has a cooling chamber filled with calcium ammonium nitrate crystals — the type used in instant ice cold packs. By adding water to the chamber, the crystals activate and cool the hydrogel to operating temperatures within 30 seconds.

“We were able to optimize the delivery device so that it not only rapidly cools the hydrogel but also holds it at that temperature, giving users a 10-minute window to fill penetrations in the eye,” Whalen said. “It’s very simple to use — almost like caulking a bathroom seal.”

The customized seal and delivery device will also reduce the amount of time it takes to close penetrating eye injuries overall.

“This temporary intervention could decrease repair time from 30 minutes or longer to less than five minutes, freeing up valuable time for first responders and trauma units,” said principal investigator Mark Humayun, University Professor of Ophthalmology and co-director of the USC Roski Eye Institute, director of the USC Institute for Biomedical Therapeutics and a professor of biomedical engineering at USC Viterbi.

To establish the material’s efficacy, a rabbit model was used. Results showed that when applied to eyes with penetrating injuries, the hydrogel improved pressure within the eye, which may be critical for preventing retinal detachment that can ultimately lead to vision loss. There also was no evidence of inflammation or infection for up to four weeks of use. The researchers hope to initiate clinical safety testing in humans in 2019.

Whalen envisions applications for the hydrogel that go beyond the battlefield.

“First responders at a mass casualty incident could deploy the hydrogel while patients wait for their injuries to be completely repaired by an ocular surgeon in appropriate microsurgical facilities,” he said. “It could also be useful in ERs in rural areas where there isn’t an eye center with such capabilities nearby. It may even have potential for temporarily treating gunshot wounds.”

Science Translational Medicine – A reversible thermoresponsive sealant for temporary closure of ocular trauma. Dec 6, 2017. Niki Bayat, Yi Zhang, Paulo Falabella, Roby Menefee, John J. Whalen III*, Mark S. Humayun and Mark E. Thompson

A sealant to save sight

Traumatic eye injuries require rapid treatment to prevent deterioration of vision. As an alternative to suturing or adhesives, Bayat and colleagues developed a temperature-responsive synthetic hydrogel that acts as a temporary sealant. Testing the hydrogel in a model of open globe injury in rabbits showed that the sealant was easily deployed from a custom-designed temperature-controlled syringe device and preserved intraocular pressure without evidence of chronic inflammation or toxicity. After gelation, the sealant could be removed by exposure to cold water. In combat or low-resource settings, this hydrogel could close wounds temporarily to prevent further tissue damage or vision loss before surgery.

Abstract

Open globe injuries are full-thickness injuries sustained to the eye wall (cornea or sclera), which cause immediate drops in intraocular pressure that may lead to retinal detachment and permanent vision loss if not treated rapidly after injury. The current standard of care for open globe injuries consists of suturing the margins closed, but the technique can be time-consuming, requires specialized training and equipment, and can lead to patient discomfort, abrasion, and infection from eye rubbing. We engineered an injectable, thermoresponsive sealant (TRS) and a custom tool to occlude open globe injuries. The smart hydrogel sealant consists of physically cross-linked N-isopropylacrylamide copolymerized with butylacrylate. At low temperatures, it can be injected as a liquid, and when raised to body temperature, a heat-induced gelation converts the hydrogel into a solidified occlusion. The sealant can be repositioned or removed without causing additional trauma via exposure to cold water. In vitro and ex vivo assessments of mechanical adhesion to eye tissue revealed maintenance of intraocular pressure that is five times greater than the physiological range with reversible seal strength comparable to cyanoacrylate (super glue). In vivo assessment in a rabbit model of ocular trauma demonstrated ease of use for TRS deployment, statistically significant improvement in wound sealing, and no evidence of neurotoxicity, retinal tissue degradation, or significant chronic inflammatory response after 30 days of exposure. Given the advantages of body heat–induced gelation, rapid reversible occlusion, and in vivo safety and efficacy, shape-adaptable TRSs have translational potential as smart wound sealants for temporary occlusion of surgical incisions or traumatic injuries.

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