Cornea made from pig collagen restores sight in blind, visually-impaired people
- Keratoconus, which is a corneal eye disease that causes vision loss, affects between 50 to 200 out of every 100,000 people.
- About 12.7 million people around the world are currently waiting for a corneal transplant.
- Researchers from Linköping University in Sweden have designed a new, widely affordable corneal implant made from pig skin to help keratoconus patients.
- The research team also developed a less invasive method for performing a corneal transplant on people with keratoconus.
Keratoconus is a disease where the cornea of the eye thins and bulges, causing vision loss. The eye disease affects between 50 to 200 of every 100,000 people globally.
Although there are currently some treatment options available for keratoconus, they do not work for all people. Some people will ultimately require a corneal transplant to regain their entire vision.
Although corneal transplants are frequently performed — almost 185,000 occurred in 116 countries in 2012 — there remains a need for corneal material to transplant. An estimated 12.7 million people are currently waiting for a corneal transplant.
Now, researchers from Linköping University in Sweden have bio-engineered a new corneal implant made from pig skin and designed a less invasive method for performing a corneal transplant on people with keratoconus.
Following a pilot study in Iran and India, 20 patients who were blind or on the verge of losing their sight due to advanced keratoconus had their sight restored after two years.
This study was recently published in the journal Nature Biotechnology.
How does keratoconus affect the cornea?
In the eye, the cornea is the dome-shaped, outermost clear layer responsible for helping you see. The cornea controls how much light enters the eye, triggering the sight process. Additionally, the cornea helps protect the eye from bacteria and dirt and also filters some ultraviolet light when you’re out in the sun.
Keratoconus is characterized by a weakened cornea that loses its natural shape and starts to bulge, eventually becoming cone-shaped.
Eye doctors do not know what causes keratoconus, although researchers believe environmental and genetic factors may play a role. For example, past research shows a family history of keratoconus may make a person more susceptible to the disease. Another study found people who are Latino and Black had a higher chance of developing keratoconus than people who are Caucasian by 43% and 57%, respectively.
Keratoconus causes the cornea to become misshapen, affecting vision. Eye doctors can sometimes correct mild keratoconus with the use of eyeglasses or specific types of contact lenses, such as rigid gas-permeable contacts, scleral lenses, or piggyback lenses.
Doctors can also treat eye disease through cornea collagen crosslinking, which helps strengthen the cornea.
If this treatment does not help, the last resort for keratoconus is a corneal transplant.
Using animal collagen for an implant
Since a large proportion of the eye’s cornea is made from the protein collagen, researchers used highly-purified collagen molecules from pig skin to create an alternate corneal material.
According to the researchers, pig skin is easily accessible as it is a byproduct of the food industry. Additionally, while doctors must use donated human corneas within two weeks, they can store the pig skin-based implants for up to two years.
“We’ve made significant efforts to ensure that our invention will be widely available and affordable by all and not just by the wealthy,” says Dr. Mehrdad Rafat, an adjunct associate professor at Linköping University and founder and CEO of the company LinkoCare Life Sciences AB, which developed the bioengineered corneas used in the study. “That’s why this technology can be used in all parts of the world.”
According to Dr. Benjamin Bert, an ophthalmologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA, while in the United States eye banks and registered organ donors help make human corneas available for transplants, that is not the case in other parts of the world.
“Internationally especially there is a dearth of human corneal donor tissue to be used for these types of surgeries — it is a huge issue,” he explained. “And so these developments in this technology do have the potential to make a huge impact in those communities.”
From full transplant to implant
According to the research team, current corneal transplant methods include surgically removing a person’s damaged cornea and stitching in place a donated cornea.
“Because it is foreign human tissue, the patient must receive immunosuppressive eye drops for at least a year and must come back to the clinic several times for adjusting, replacing, and removing the sutures,” explained Dr. Neil Lagali, professor at the Department of Biomedical and Clinical Sciences at Linköping University and leader of the research group that developed the new keratoconus surgical method. “Even then, vision is not optimal and requires further corrective refractive procedures.”
Dr. Lagali told MNT through this new less invasive implant method, the patient keeps their own cornea. A surgeon makes a small incision within it and inserts the bioengineered implant.
“The implant does not have cells, so it does not trigger an immune response, and only an 8-week course of immune suppression eye drops are needed,” he continued. “No sutures are needed, so the procedure can be performed in a single hospital visit. We showed that this procedure has the potential to give 20/20 vision to initially blind patients without using donor tissue.”
Dr. Lagali and his research team also found the new implant method avoided inflammation and the wound healing was very fast.
“Having implants instead of a full transplant helps to retain more of the patient’s own tissue, which of course is preferable to prevent issues with rejection, neovascularization, or other complications that can happen,” Dr. Bert commented.
Researchers conducted a pilot clinical study involving 20 people with advanced keratoconus. Of the patient group, 14 were fully blind and the remaining six were on the verge of losing their vision before surgery. Surgeons in Iran and India conducted the new implant method using bioengineered corneal material.
The research team reported no complications immediately following the procedures, nor throughout the two years they followed study patients.
Two years after surgery, the 14 participants were no longer blind. And three participants who had no vision before the procedure had 20/20 vision afterward.
When will it be available?
Dr. Lagali hopes surgeons will adopt this method as a simpler, safer approach to treating advanced keratoconus, even if they use donor tissue.
“Because it does not require suturing skills and it does not open the eye, it could potentially be performed with less surgical training and in more locations,” he explained.
“Our ultimate hope is that the simplified procedure will be able to reach visually impaired people with poorer access to advanced healthcare. (And) our bioengineered implant removes the reliance on donor tissue and eye banks, so it could be shipped where it is needed.”
— Dr. Neil Lagali, lead researcher
Dr. Lagali said the next step in their research is to conduct randomized clinical trials with a larger number of patients.
“We are working on getting funding for that,” he said, adding: “Once we can demonstrate this works in a randomized trial, then we will apply for authorization to market this as a product. In terms of the new surgical procedure, it is not patented and is free for surgeons to use, and we hope they will try it with human donor tissue.”
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