Cornea transplantation, commonly called keratoplasty, is an optical procedure where the damaged or scarred corneal tissue is replaced with a healthy tissue obtained from a donor.
Corneal grafting specifically replaces damaged central corneal tissue. The healthy corneal tissue is usually obtained from an eye bank. When corneal health deteriorates, it can lead to vision problems like distortion, light scattering, blurred vision, and glare. To restore functional vision, cornea transplantation is the only fruitful way.
How Will You Know if a Corneal Transplantation is Required?
If your corneal damage is not major, you may not require a keratoplasty surgery. In such cases, alternative options like laser procedures or contact lenses can be utilised to enhance vision. However, when your cornea’s clarity is significantly compromised, adversely affecting your vision, then the optometrist focuses on treating the underlying causes of the damage. If they find the damage to be severe, corneal transplantation is suggested. Some conditions that may require corneal graft surgery are listed below.
- Corneal scarring is a condition caused by infections like herpes simplex or keratitis
- Keratoconus and other corneal thinning disorders
- Corneal swelling
- Corneal dystrophies like Fuchs’ endothelial dystrophy
- Complexities post cataract and other eyes surgeries
- Cornea injury due to chemical burns
- Corneal grafting rejection from previously conducted corneal graft surgery.
Variants of Cornea Transplant
Innovations in corneal transplantation have revolutionised the potential to replace either the entire or specific portions of the cornea. Opting for a minimally invasive approach, like partial keratoplasty, offers numerous advantages, including reduced risks and shorter recovery periods. Below are the common cornea transplant procedures employed on people with corneal issues.
- Penetrating Keratoplasty (PK): It is a traditional treatment that involves a full-thickness transplant of the cornea.
- Endothelial Keratoplasty (EK): This is a more advanced technique and is also known as a back layer cornea transplant. This is a procedure that aims to restore vision in case of corneal inactivity due to bullous keratopathy, Fuchs dystrophy, and other disorders associated with endothelial.
- Anterior lamellar keratoplasty: This process involves the extraction of your outer corneal layer and replacing it with that of a healthy individual donor. This method is commonly employed for patients with scarring of the corneal uppermost layer and keratoconus.
- Keratoprosthesis: This is the process where the cornea is entirely replaced with an artificial cornea. When your cornea is completely or severely damaged, which cannot be rectified with the cornea of a natural donor, this is the only effective means.
What Happens Before a Corneal Graft Surgery?
After deciding to turn for corneal transplantation, your name and details are added to the waiting list of a nearby trusted eye bank. The availability of a suitable eye donor’s tissue may take between a few days and a few weeks.
Prior to being utilised for a keratoplasty, the cornea of a donor undergoes a comprehensive examination to assess its clarity. Plus, it undergoes rigorous screening for diseases like AIDS and Hepatitis. These evaluations adhere to the stringent medical standards penned under different governance across the globe. The corneal tissues that satisfy all these guidelines are selected for corneal graft surgery. This meticulous process guarantees the safety and health of the recipient of the graft.
What to Expect During Keratoplasty?
The process of keratoplasty is carried out precisely following several standardised steps. Below are the common procedures that take place during this surgery.
- The first step during keratoplasty is administering anaesthesia. Your doctor will either administer local or general anaesthesia as per your case. The factors influencing this decision include your age, specific eye condition, overall health, and personal preference.
- If you are given a local anaesthetic, it is introduced to your eye through an injection. Soon you will find the muscles of that region relaxed, inhibiting eye movement and blinking mechanism and making your eye numb. Throughout the procedure, you will remain awake.
- When the anaesthetic shows its effects, by using an instrument known as lid spectrum, your eyelids will be kept open.
- Further, your optometrist will carry out the needed measurement of the corneal area and conclude the required size of eye donor tissue.
For Penetrating Keratoplasty
• If you opt for penetrating keratoplasty, in the traditional procedure, a full-thickness portion of tissue shaped like a button is extracted from the diseased or affected area using the instrument like trephine or lasers like femtosecond.
• The tissue from the donor is used in the matching button-shaped pattern, is positioned over the extraction area, and then, is precisely sutured. After the surgery, these sutures will remain intact for as long as a year or more.
• For optimising healing, a plastic shield is kept over the eye.
• The whole procedure takes a maximum of a couple of hours, and no prolonged stay in the medical facility is required.
For Endothelial Keratoplasty
- In this corneal transplantation procedure, the cornea selectively replaced. It is associated with removing the cornea’s innermost layer (endothelium) while keeping the healthy overlying tissue as it is. The corneal fluid balance is maintained by the endothelium; a damaged endothelium means swelling of the corneal area and the chances of vision loss.
- Endothelial keratoplasty begins with a small incision. The surgeon put a thin disc obtained from the donor on the patient’s cornea’s back surface.
- With the help of an air bubble, the new layer of endothelium is properly placed.
- The incision made initially needs no further procedure to seal. It is a self-healing wound that does not require any stitches.
What Happens After Keratoplasty?
Every detail of the expected changes in your eyes will be discussed by your optometrist. Usually, patients return home on the same day, provided they have someone to accompany them. You should diligently follow the postoperative instructions and be on the prescribed medicine as recommended. You have to take steroid drops for several months so that the graft used is accepted by your body. Moreover, anti-infection and swelling-diminishing medications are a must. For several days, you will have to wear a pair of protective gear to avoid any dust particles or harsh light entering your eyes.
Immediately consult your doctor if you experience any complications. The symptoms might include pain, sensitivity to light, redness, and vision decrease.
For a short while post-surgery, your visibility will be almost nil as the transplant starts to heal. As per data, most individuals who go through any of the cornea transplantation processes experience improved sight for several years.
Are You Eligible for Donating Corneal Tissue?
The recent advancements in the field of medicine have made it possible for people above the age of 65 years to donate corneal tissue, unlike previously. However, according to the Cornea Donor Study, there is a 75% chance of you being an ideal donor if you have a healthy cornea and are in the age group of 34 to 71 years. In the USA, it is found that 3/4th of the corneal donations are done by individuals between the mentioned age group, and 1/3rd is done by individuals in the aged group of 61 to 71 years.
As individuals below 34 years of age have healthier and well-performing corneas, it is suggested that the younger patients get the cornea of younger donors. Many organisations like NHS Organ Donation and the American Academy of Ophthalmology accept such donations after testing the candidates’ eye health rigorously.
Risks Associated with Corneal Transplantation
Even though cornea transplantation is a safe procedure, there are some associated risks.
- Graft rejection (elaborately discussed further) may occur.
- The risk of postoperative infections like bacterial, viral, and fungal keratitis is predominant.
- Graft failure is a situation where the transplanted cornea does not properly integrate and cannot function optimally. As a result, the graft fails to be a part of the body.
- Astigmatism is the formation of an irregular corneal curvature that distorts vision.
- Some patients witness increased inocular pressure within the eye, requiring over-the-counter medication.
Rejection of the Corneal Graft
A corneal graft is rejected as a consequence of a complex immunological response that results after a keratoplasty surgery. In these cases, the immune system of the recipient considers the transplanted cornea to be a foreign entity, thus imparting an immune response against it. Even though there have been numerous advancements in the techniques associated with corneal transplantation, along with the emergence of immunosuppressive medicines, rejection of graft remains a potential concern.
The severity of rejection varies from person to person. Common signs of corneal graft rejection include redness, pain, and decreased vision. Besides, you will sense an increased sensitivity to light and a hazy appearance. It is crucial to promptly report any of these symptoms to your optometrist to ensure timely management.
Several risk factors contribute to the likelihood of corneal graft rejection. These include a history of previous graft rejection, pre-existing ocular surface inflammation, or infection. Furthermore, incompatible blood types between the donor and recipient and non-compliance with the immunosuppressive medication regimen are also responsible for such events. In addition, certain corneal diseases, like herpes simplex keratitis and corneal vascularisation, elevate the risk of rejection.
Managing corneal graft rejection primarily involves a combination of immunosuppressive medications like corticosteroids and various immunomodulatory agents. These two treatments work together to suppress the immune response and reduce inflammation. During the treatment, the patient needs to be monitored closely with frequent follow-ups to check the status of the graft.
Minimising Graft Rejection Risks
Preventing corneal graft rejection is a primary goal in transplantation. This is achieved through keen donor tissue selection, careful surgical technique, and adherence to postoperative care guidelines. Using immunosuppressive medications before and after the procedure helps to minimise the risk of rejection.
Artificial and Biosynthetic Corneas
Also known as keratoprosthesis, artificial corneas are innovative findings that help in restoring vision among people with corneal blindness. This solution is employed specifically when corneal transplantation fails to help the patient. This is a highly recommended advanced technology that is seen as a promising alternative for traditional transplantations.
Artificial corneas are synthesised using biocompatible materials, like polymers or plastics, designed to replace the damaged or diseased cornea. They consist of an optical component that restores vision. With that, they have a supporting structure that allows integration with the surrounding eye tissue. These devices can be manufactured in various shapes and sizes to match individual patient needs.
On the other hand, biosynthetic corneas involve bioengineered materials that counteract the structure and function of the natural cornea. These constructs aim to replicate the biological properties of the cornea for long-term positive outcomes. Biosynthetic corneas can be composed of synthetic materials and biological components, like collagen or stem cells, to facilitate cellular integration and tissue regeneration.
Takeaway
Cornea transplantation is a transformative procedure that offers an improved vision for individuals with corneal diseases, injuries, or impairments. Although there are potential risks associated with the surgery, the majority of corneal transplantations are successful in restoring functional vision. Ongoing advancements in surgical techniques, immunosuppressive medications, and alternative approaches like artificial and biosynthetic corneas are making positive advancements in the field to increase success rates.
