Profound vision loss can occur in people living with keratoconus. The progressive corneal thinning of the abnormally-shaped cornea causing nearsightedness and astigmatism typically worsens over time. Meanwhile, corneal pain, sensitivity to light, and/or experiencing persistent “dry eyes” can also affect people living with severe keratoconus. While addressing nearsightedness and astigmatism through the use of corrective lenses or minimally-invasive surgery can alleviate the symptoms of early-to-moderate keratoconus, a corneal transplant may be needed for keratoconus-afflicted adults with severe symptoms.
The Precision Keratoconus Center can assist you in determining which type of treatment may be most appropriate for your needs and life circumstances.
What is a Cornea Transplant?
Removal of the cornea and replacement with a “donor” cornea occurs in a cornea transplant. Cornea transplants are usually performed in an outpatient surgical setting, and either local or general anesthesia is utilized. In a penetrating keratoplasty (PKP) procedure, the entire cornea is removed and replaced. However, keratoconus-afflicted people who undergo a partial thickness corneal transplant (called an endothelial keratoplasty) have their properly-functioning corneal layers left “intact” and only the affected layers of their corneal tissue removed and replaced.
In either case, the deceased donor’s cornea needs to be a tissue-type “match” so the donor tissue is not rejected when transplanted into the recipient. According to the National Keratoconus Foundation (NKF), the risk of rejection of the donor’s corneal tissue is highest in the first two years after the transplant surgery.
Immunosuppressant Medications and Cornea Transplants
An immune system reaction to a perceived “foreign body” is the main reason that rejection of the cornea transplant (or any other organ transplant) occurs. For this reason, immunosuppressant medications are normally required by people who have received an organ transplant for the rest of their lives. A medical research article in the Journal of Ophthalmic and Vision Research in 2017 reported the following as five of the most common immunosuppressant medications used in high-risk corneal transplant patients (i.e., patients with a high level of corneal vascularization):
- Cyclosporine A;
- Mycophenolate mofetil;
Oral immunosuppressant drugs are often prescribed to patients following a corneal transplant, in addition to daily eye drops containing immune system-suppressing medications. However, taking immunosuppressant drugs can lead to a heightened risk for an infection since the immune system is weakened.
Glaucoma Risk, Immunosuppressant Medications, and Corneal Transplants
Topical steroid use has been linked to elevated intraocular pressure in 35 percent of all people prescribed this type of immunosuppressant medication. While people who have normal intraocular pressure can actually have glaucoma, high intraocular pressure usually precedes glaucoma and is considered a significant risk factor for its development.
According to the Glaucoma Research Foundation, high intraocular pressure alone does not cause glaucoma. However, high intraocular pressure can cause optic nerve damage, and the resulting optic nerve damage can cause blindness. Meanwhile, topical corticosteroids are the usual treatment regimen for corneal transplant recipients experiencing rejection of the transplanted tissue.
Three Cornea Transplant Rejection Signs
Corneal edema (swelling) is one of the most common signs of cornea transplant rejection (per the American Academy of Ophthalmology). Another sign is the presence of stromal blood vessels in one (or more) quadrants of the cornea. Keratic precipitates on the donor epithelium following transplantation into the recipient is a third sign that cornea transplant rejection is occurring.
Notably, keratoconus-afflicted people who have previously experienced a total cornea transplant rejection are at higher risk of rejection following another cornea transplant operation. Therefore, preventing rejection is a high priority during (and following) cornea transplantation.
How Successful are Cornea Transplants?
Cornea transplants can restore vision in many keratoconus-afflicted people who have progressed to legal blindness. Indeed, the success rate for cornea transplantation in “low-risk” cornea transplant patients is considered to be at 95 percent. On the other hand, the success rate in “high-risk” patients is far lower.
While immune system reactions resulting in rejection occur in 18 percent of “low-risk” patients, these reactions occur in 75 percent of “high-risk” cornea transplant patients (per an article in BMC Ophthalmology).
By scheduling an appointment at one of the numerous Precision Keratoconus Center sites, you can learn more about preparing for cornea transplant surgery.