Definition and Overview

Keratoplasty refers to any type of surgical procedure performed on the cornea, or the transparent front part of the eye that covers and protects the pupil, anterior chamber, and iris. The objective of the procedure is to restore the function of the diseased or damaged cornea, which contributes to around two-thirds of the eye’s total optical power.

One of the most common types of keratoplasty is corneal transplantation or grafting, which involves replacing the damaged cornea with a graft or corneal tissue from a donor. Ideal donors are individuals who have very recently passed away and did not have any diseases or conditions that affected their corneal tissues.

There are two general kinds of corneal transplantation, namely:

  • Penetrating keratoplasty, or when the patient receives an entire cornea for transplantation; and
  • Lamellar keratoplasty, or when the patient receives only a partial corneal graft
    Patients might be referred to an ophthalmologist for a keratoplasty for the following reasons:

  • For the improvement of visual acuity, especially in cases where the cornea has turned opaque or became distorted

  • For tectonic or reconstructive purposes, especially when a disease or injury affects the anatomy or integrity of the cornea
  • To remove inflamed corneal tissue, especially when the cornea is not responding to medications such as antibiotics
  • To improve the appearance of corneal scars, especially those that developed a white, opaque appearance.

Aside from corneal tissues sourced from human donors, a keratoplasty can also use synthetic corneas. These are recommended for patients who cannot find a compatible human donor, or those living in places where a corneal donor is rare. Below are some types of synthetic corneas:

  • Boston keratoprosthesis - This type is widely used and developed by the Massachusetts Eye and Ear Infirmary.
  • AlphaCor - This type is recommended for patients who have undergone several corneal grafts with little to zero success
  • Osteo-Odonto-Keratoprosthesis - This is a rare type of synthetic cornea often recommended for disabled patients. However, the replacement procedure using this synthetic cornea is quite complex and involves multiple steps, including using a lamina sourced from the patient’s teeth and grafting it into an artificial lens.

A keratoplasty can be performed on an outpatient basis, with the patient coming in for regular follow-up consultations after the procedure to prevent infections and ensure the overall success of the operation.

Who Should Undergo and Expected Results

Patients with the following conditions can be candidates for a keratoplasty:

  • Scarring in the cornea caused by illness, injury, or infection (such as herpes of the eyes or fungal infections in the cornea)
  • Poor vision that cannot be restored or augmented by prescription lenses (such as eyeglasses or contact lenses)
  • Painful inflammation of the corneal tissue, which does respond to treatment
  • Scarring of the cornea caused by trichiasis, a condition that involves the inward growth of eyelashes
  • Edema, or excessive swelling of the cornea.
  • Fuchs’ dystrophy and other hereditary conditions affecting the corneas
  • Conditions that cause corneal thinning
  • Chemical burns to the cornea
  • Rejection of grafted corneal tissues from a previous keratoplasty procedure
  • Complications of a LASIK or cataract surgery

In most cases, keratoplasty can successfully restore the patient’s vision and improve corneal and ocular health.

How Does the Procedure Work?

The way a keratoplasty is performed depends on the specific type of corneal transplant the patient requires. With a human donor, the corneal tissue must be harvested within 24 hours of the donor’s death.

  • Penetrating keratoplasty - In this procedure, the doctor will remove the corneal tissues from the human donor and the patient’s damaged cornea with a circular cutting device called a trephine. The graft will then be sewn into place using tiny sutures. The doctor will apply antibiotic eye drops to the patient’s eyes before placing a sterile dressing over them. The patient will be discharged after the anesthesia wears off. The first post-surgery consultation will be scheduled the day after the procedure.

  • Lamellar keratoplasty - This procedure is similar to a penetrating keratoplasty, but instead of a whole corneal graft, the doctor will replace only the diseased corneal layers and preserve the rest of the healthy tissues.

Possible Risks and Complications

Corneas are slow to heal when compared to other parts of the body because they are not connected to blood vessels that can speed up the healing process. This increases the risk of infection. Thus, patients are strictly advised to use antibiotic eyedrops until they have fully recovered from the procedure

Another risk of the procedure is the rejection of donor tissues, which occurs in approximately 20% of all cases.

References:

  • Chow J, Kim T. Penetrating and lamellar keratoplasty. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:vol 6, chap 26.

  • Yanoff M, Cameron D. Diseases of the visual system. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 431.

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