Are Eye Transplants on the Horizon?

The human body is incredibly resilient, and even after parts of it have been destroyed, it can accept foreign tissue via transplants–in certain circumstances–and continue to function as if nothing ever happened. Doctors today can transplant organs such as hearts, lungs, kidneys, and others from one person to another; there’s even a doctor who wants to perform a head transplant by next year. One organ that still cannot be transplanted is the eye, but thanks to a team of doctors and researchers in Pittsburgh, Pennsylvania, that may not be the case for very long.

Dr. Kia Washington, a plastic surgeon at the University of Pittsburgh Medical Center, is leading a research team with the goal of performing the first successful human eye transplant. She hopes that the procedure will be ready within the next 10 years.

In the United States, over one million people have vision impairments as a result of injuries. In fact, traumatic eye injuries are the fourth most common cause of combat injuries for American soldiers, which is why the Department of Defense is sponsoring Washington’s research: If she discovers a procedure for eye transplants, then it will go a long way toward treating soldiers, as well as the thousands of civilians who have impaired vision or no vision at all due to injuries.

Of course, this is all much easier said than done. A successful eye transplant would require, for one, a way of keeping the optic nerve alive during the procedure and reattaching it to the new host’s brain. Normally, upon removal, the cells in the optic nerve die immediately, thus rendering the eye useless; even if they didn’t, the new optic nerve would need to grow from the eye all the way back to the brain, which is no small feat.

However, one of Washington’s colleagues recently published a paper indicating that a cocktail of drugs, including the multiple sclerosis drug 4-AP, could help blind mice regrow their optic nerves and regain their sight after injury. This procedure, if replicable in humans, could lead to successful eye transplants. Although it is a “moonshot,” transplanting eyes in the next 10 years would be an incredible achievement that would help to treat cases of injury-related vision loss.

Keratoconus and New Stem Cell Research

Did you know the cornea is the only living tissue that has no direct or indirect connection to blood vessels to obtain the oxygen and nutrients it needs to remain healthy? Instead, it absorbs oxygen from the outside air (diffused through the tears) and it gains nutrients from the inside using the aqueous humor (fluid that fills the chamber behind it).

According to WebMD, we see through the cornea, which can be described as the clear outer lens or “windshield” of the eye. Normally, the cornea has a dome shape, like a ball. Sometimes, however, the structure of the cornea is just not strong enough to hold this round shape and the cornea bulges outward like a cone. This condition is called keratoconus.

Keratoconus is a progressive non-inflammatory disorder that causes a characteristic thinning and cone-like steepening of the cornea. According to WebMD, it is caused by a decrease in protective antioxidants in the cornea. The cornea cells produce damaging by-products, like exhaust from a car. Normally, antioxidants get rid of them and protect the collagen fibers. If antioxidants levels are low, the collagen weakens and the cornea bulges out.

How is Keratoconus treated?

Treatment usually starts with new eyeglasses. If eyeglasses don’t provide adequate vision, then contact lenses, usually rigid gas permeable contact lenses, may be recommended. With mild cases, new eyeglasses can usually make vision clear again. Eventually, though, it will probably be necessary to use contact lenses or seek other treatments to strengthen the cornea and improve vision.

However, most recently, researchers in Japan and Wales found that human cells reprogrammed to become stem cells were able to form cornea tissue in lab dishes. This was reported on March 9th in the Science and Medicine publication, Nature. The stem cell tissue was used to repair the damaged outer layer of the cornea in rabbits. In a separate study also published March 9 in Nature, researchers in China and the United States coaxed stem cells in the eyes of a dozen babies born with cataracts to regrow clear lenses.

The researchers also studied 37 babies who were born with cataracts. Regular cataract surgery, which involves removing the cloudy lens and replacing it with a plastic one, was done for 25 of the babies. In the remaining 12 babies, doctors made a small incision in the side of the sack containing the lens and extracted the cataract, but didn’t replace the lens. Stem cells in the sack generated a new lens within about three months of surgery.

While both studies are technically proficient and provide new approaches to treating cataracts or corneal injuries, neither will soon be ready for widespread use in the clinic, says Henry Klassen, an ophthalmologist at the University of California, Irvine School of Medicine.

Sources:

https://www.sciencenews.org/article/new-techniques-regrow-lens-cornea-tissue#video 

http://www.bbc.com/news/health-28106253

http://www.webmd.com/eye-health/eye-health-keratoconus

4 Signs of Graft Rejection

corneal_transplant Hargrave Eye Center BlogA cornea transplant is most often used to restore vision to a person who has a damaged cornea. A cornea transplant may also relieve pain or other signs and symptoms associated with diseases of the cornea.

In corneal transplant surgery the scarred or damaged cornea is removed and replaced by a human donor cornea called a graft. Corneal transplant surgery also is called penetrating keratoplasty or corneal grafting. Your eye is the recipient eye because it receives the graft. The other person’s cornea is the donor cornea or donor tissue because the cornea is being donated or given to you.

There always is a possibility that the body will reject the graft. This is like an “allergic” reaction of the body against the donor cornea. It can occur any time after the surgery. There is a good chance this can be treated successfully if you act immediately. There are four danger signs you must know, according to the University of Michigan Kellogg Eye Center in Ann Arbor.  If any of these occur and last for more than 12 hours, you should call your ophthalmologist – even if it is a weekend or a holiday.

To remember the signs of graft rejection, remember the letters: R S V P:

Redness – For a few weeks after surgery, your eye may be red. If at any time your eye begins to get redder, you should call your ophthalmologist. You easily can check the redness of your eye by looking into a mirror and pulling down the lower lid. Look carefully at the white part of the eye, especially in the area next to the cornea.

Sensitivity to light – Bright lights may seem irritating to your eye after surgery. This, too, slowly should get better. If you notice your eye becoming so sensitive to light that you feel like covering it, you should call your ophthalmologist.

Vision changes – Your vision most likely will improve gradually after your surgery. Make a habit of checking your vision every day. Check it at about the same time and in the same light. Pick an object in your house that has some pattern or detail to it. Look at the object with your operated eye while covering the other eye with your hand. If your vision seems to be getting worse, you should call your ophthalmologist.

Pain – It is normal to have occasional small twinges of pain in your eye. If your eye develops constant pain or dull aching that lasts several hours, call your ophthalmologist.

Make a habit of checking your eye every day. Check your vision at about the same time and in the same lighting each day, perhaps at the same time you do another routine activity, such as brushing your teeth.

Source: Mayo Clinic WebsiteUniversity of Michigan Kellogg Eye Center