The cornea is a transparent layer that protects the eye, covering the iris, pupil, and anterior chamber. It works with the lens to focus light onto the retina and accounts for approximately two-thirds of the eye's total optical power. A healthy cornea is, therefore, incredibly important to good vision.
The cornea contains corneal epithelium stem cells that allow it to regenerate and repair when it becomes damaged. These stem cells, however, can be destroyed by disease (such as infection) or by trauma (for example, objects entering the eye). When these stem cells are lost, the corneal epithelium is unable to repair and renew itself. This results in epithelial breakdown and persistent corneal defects, such as corneal opacity, scarring and chronic inflammation. All of these contribute to loss of corneal clarity and potential loss of vision.
Currently it is possible to perform corneal transplants replacing the damaged cornea with a cornea taken from a donor who has died. However good-quality tissue is scarce: in the UK approximately 250,000 people receive corneal transplants every year, but this figure is approximately 21% less than is needed. In addition, conventional corneal transplant operations are not always successful; donor corneas are prone to rejection by the patient because immune cells from the donor are implanted along with the rest of the cornea. Rejection is when the organ recipient's immune system recognises the donor organ as foreign and attempts to eliminate it. An alternative is therefore needed in order to treat patients who have suffered damage to their cornea but are not selected to receive a transplant, or whose bodies reject a donor cornea.
A team led by ophthalmologist Kohji Nishida at Osaka University may have created a new treatment for those suffering from corneal disease by using sheets of tissue made from induced pluripotent stem cells (IPS cells). Stem cells are the blank tiles of the human body with the capacity to develop into cells of different types. Scientists at Osaka University have developed a method of reprogramming IPS cells from a donor into an embryonic-like state that can then transform corneal cells.
On 25 July 2019 a patient with very poor vision because of corneal epithelial stem cell deficiency – her corneal stem cells were damaged and her cornea was unable to regenerate - underwent treatment during which sheets of IPS cells were implanted into her left eye. After treatment, she was monitored in hospital for almost one month before being discharged. Upon leaving hospital she had considerably improved vision from her left eye and it has been reported that this treatment has been a success. To date the patient has not experienced any problems with the transplanted tissue: the team at Osaka University have said that the IPS cells do not contain immune cells, so are unlikely to be rejected like a traditional cornea transplant, and one transplant should remain effective throughout a patient’s lifetime.
Arran Macleod, a solicitor in the clinical negligence team at Penningtons Manches Cooper LLP, said: “This is an encouraging development. We act for clients who, as a result of infection or traumatic injury to their eyes and delays in diagnosing and treating those conditions, suffer from corneal disease and permanent loss of vision. We would welcome a new treatment which would restore the damaged corneal epithelium and enable our clients to have the opportunity of having improved vision for the rest of their lives. We will continue to monitor this research and subsequent developments with interest.”