Preserving Vision with Hydrogel
High axial myopia, or extreme nearsightedness, is one of the world’s leading causes of blindness. The condition stems from weakness in the sclera, the eyeball’s white outer wall, which causes it to deform even under normal pressure within the eyeball. James Su, a graduate student researcher co-advised by MSE and Bioengineering Professor Kevin Healy and School of Optometry Professor Christine Wildsoet, is developing a promising new treatment for the condition, based on a synthetic biomaterial known as hydrogel.
“The area hasn’t seen much research, because it isn’t prevalent in the United States,” Su explains, “but it’s a big problem in Asia, where myopia is at least three times more common than it is here. About 10 percent of the myopic population in Asia has a refractive error measuring –6 diopters or worse, which is considered high myopia.”
Inside such an eyeball, intraocular pressure causes it to elongate backwards, like a balloon squishing back when squeezed around its sides. In most cases, this just throws the eye’s focus off, requiring corrective lenses, but high axial myopia can lead to blinding complications such as retinal detachment, macular degeneration, cataracts and glaucoma. Sufferers rely on thick glasses or Lasik surgery, but even Lasik might be only a temporary fix as eyesight continues to decline — and most people’s corneas will withstand only one or two laser treatments in a lifetime.
“People who wear lenses or get Lasik think that the problem goes away,” says Su, “But these just treat the eye’s refractive error. That is just the symptom, not the underlying cause.”
To address the cause of the problem, you have to strengthen the eyeball against internal pressure so that it resists elongation, Su explains. One experimental treatment, which originated in Russia decades ago, involves suturing reinforcing strips around the back of the eyeball, which act like rubber bands pushing the sclera forward. These “scleral bands” are typically made out of donated eye tissue, which is scarce, or Teflon, which can cut into the eyeball underneath. Either way, sewing them on is a delicate and risky operation.
To simplify the treatment, Su uses a more advanced material, a biodegradable “functionalized biomimetic hydrogel,” which is an injectable liquid at cool temperatures that becomes a soft rubber-like solid at body temperature. The surgical procedure, which is currently undergoing animal testing, begins with a dose of local anesthesia; then the hydrogel is injected into the back of the eyeball under the Tenon’s capsule, a thin sheath that surrounds the posterior eyeball over the sclera. The gel conforms to the shape of the eye wall, then warms up and stiffens, adding strength. Because the hydrogel never enters the vitreous humor or touches the cornea, the procedure is safer and less invasive than the existing operation.
The hydrogel may also be formulated to contain and release drugs to enhance treatment. If an allergic reaction occurs, the gel will be easy to remove. One of the benefits is that patients will require injections just twice a year or less, a simple outpatient procedure.
Su hopes to patent and commercialize the treatment within several years, probably launching operations in Asia. With venture backing, he thinks FDA approval could be expedited because animal data on the hydrogel are established, and the drugs are already approved for other indications.
As a second phase, the treatment can also be used preventively for children diagnosed as progressing towards high myopia. “Vision care is going in the direction of prevention,” says Su. “This reduces lifetime vision care costs, and of course it’s better for the patient for other reasons as well.”