After the transplant, the researchers followed the volunteers for two years. They concluded that the implant was safe to use and restored the thickness and curvature of the recipient’s native cornea. Before surgery, 14 of the 20 participants were legally blind and the others were visually impaired. After two years, three participants who were blind before the study had 20/20 vision due to the use of bioengineered corneas and contact lenses or eyeglasses. For the others, their visual acuity improved on average to 20/26 (Indian group) and 20/58 with glasses (Iran group).
Christopher Starr, an ophthalmologist at an Weill Cornell Medicine and a clinical spokesperson for the American Academy of Ophthalmology, said that while the study was small, the results were encouraging. “The postoperative visuals are impressive — as good as, or better than, traditional transplant techniques,” he said. Participants also required fewer eye drops and a shorter course of immunosuppressive drugs than would normally be required for corneal transplants from human donors.
There have been other corneal implant attempts. Man-made versions made of plastic exist, but they are used when a patient has failed one or more donor transplants. Because they’re plastic, these implants don’t integrate into a patient’s own eye like human tissue, increasing the risk of infection. “Biological integration has been a huge challenge,” Starr said. “Without tight biological integration of the device, there is a much higher risk of bacteria entering the eye and causing a rare but catastrophic infection called endophthalmitis, which often leads to permanent and irreversible blindness.”
Immune system rejection, in which the body attacks the implant as a foreign body, is also a risk for any type of implant. But bioengineered corneas may also have a lower risk of rejection compared with human donor tissue, because the implants have already been stripped of living cells, Starr said.
Still, the process of insertion bioengineering the original cornea instead of replacing it may have some limitations. Akpek doubted the implant would be able to treat very severe cases of keratoconus, in which the cornea becomes cloudy. “By putting a clear layer on the cornea, they’re strengthening, thickening, and flattening the cornea, but they’re not treating the cloudy cornea, which is an advanced stage of keratoconus,” she said. In order for the bioengineered implant to work in these patients, she believes the damaged cornea also needs to be removed — but that requires special training and technology, which isn’t ubiquitous.
She noted that a transplant first requires a diagnosis of corneal disease, which can be difficult in low-income settings where people don’t have access to eye specialists. “It doesn’t solve poverty,” Akpek said. But if the bioengineered version is cheaper and more accessible than using a donor cornea, she said, it could potentially prevent more people from going blind.
Rafat’s company is planning a larger trial in patients with corneal disease. more advanced disease. They also want to test the implant in people with other types of corneal blindness. One unknown is how long the bioengineered cornea will last after transplantation. Donor corneas can be used for 10 years or more if there are no complications. “Our goal is a permanent implant,” Rafat said.