Countless people suffer from vision problems ranging from blurred vision to blindness. But not everyone wants to wear glasses or contact lenses. That’s why many sufferers undergo eye surgery, including LASIK – a laser-assisted procedure that reshapes the cornea and corrects vision. However, the procedure can have unwanted side effects, which is why researchers are trying to remove the laser from LASIK by reshaping the cornea instead of cutting it in initial animal trials. Michael Hill, professor of chemistry at Occidental College, presented his team’s findings at the American Chemical Society (ACS) Fall Meeting. The ACS Fall Meeting features around 9,000 presentations on various scientific topics.
LASIK Method Could Soon be Replaced
The human cornea is a curved, transparent structure located at the front of the eye. The corneal stroma consists of orthogonally stacked collagen fibril lamellae whose molecular composition and precise macromolecular geometry eliminate backscattered light and maintain the shape of the cornea. The cornea refracts light from the environment and focuses it onto the retina, where it is transmitted to the brain and interpreted as an image. However, if the cornea is deformed, it cannot focus the light properly, resulting in blurred images. In fact, anatomical variations, birth defects, trauma and various pathologies can alter the shape, structural stability and transparency of the cornea, thus affecting vision. The LASIK method uses special lasers to reshape the cornea by removing precise pieces of tissue. This common procedure is considered safe, but has some limitations and risks, and cutting the cornea compromises the structural integrity of the eye. Hill explains, “LASIK is just a fancy way of doing traditional surgery. Tissue is still cut out – just with a laser.” But what if the cornea could be reshaped without any incisions?
This is exactly what Hill and his colleague Brian Wong are investigating using a process known as electromechanical reshaping (EMR). “The whole effect was discovered by accident,” explains Wong, a professor and surgeon at the University of California, Irvine. “I was looking at living tissue as a moldable material and discovered this whole process of chemical modification.” In the body, the shapes of many collagen-containing tissues, including the cornea, are held in place by the attractive forces of oppositely charged components. These tissues contain a lot of water, so applying an electrical voltage lowers the pH value of the tissue and makes it more acidic. By changing the pH value, the rigid attractive forces within the tissue are loosened and the shape becomes malleable. When the original pH value is restored, the tissue is fixed in the new shape. Previously, the researchers had used EMR to reshape cartilage-rich rabbit ears and to modify pig scars and skin. However, one collagen-rich tissue they were keen to investigate was the cornea.
In this work, the team constructed special platinum “contact lenses” that served as a template for the corrected shape of the cornea, and then placed them over a rabbit eyeball in a saline solution designed to mimic natural tears. The platinum disk acted as an electrode to produce a precise pH change when the researchers applied a small electrical voltage to the disk. After about a minute, the curvature of the cornea adjusted to the shape of the disk – about the same amount of time as a LASIK treatment, but with fewer steps, less expensive equipment and no incisions.
Investigation Into Which Types of Vision Correction are Possible
They repeated this procedure on 12 separate rabbit eyes, 10 of which were treated as if they had myopia or nearsightedness. In all “myopic” eyeballs, the treatment restored the desired focusing power of the eye, which corresponds to an improvement in vision. The cells in the eyeball survived the treatment as the researchers carefully controlled the pH gradient. In addition, the team was able to show in further experiments that their technique may be able to reverse chemically-induced corneal opacity – a condition that can currently only be treated by a full corneal transplant.
Although these initial results are promising, the researchers emphasize that they are still at a very early stage. Next up, according to Wong, is “a long road of detailed and precise animal experiments”, including tests on live rabbits and not just their eyeballs. They also want to find out what types of vision correction are possible with EMR, such as myopia, hyperopia and astigmatism. Although the next steps are planned, they have been put on hold for the time being due to uncertainties regarding the team’s scientific funding. “There is still a long way to go from what we have achieved so far to clinical application. But when we are ready, this technique will be widely applicable, much cheaper and possibly even reversible,” summarizes Hill.