ARTIFICIAL CORNEA TRANSPLANT
The artificial cornea transplant, referred to as a keratoprosthesis, can be used as a replacement to a human cornea transplant procedure. The definition of a keratoprosthesis is a synthetic or partially synthetic device to replace an opaque human cornea to provide a clear view through the front of the eye.
Two devices are approved for use in the US, the AlphaCor developed in Australia and the Boston Keratoprosthesis developed by Dr. Claes Dohlman, MD. Indications include previous failed human grafts, a poor prognosis for future human grafts, suboptimal vision in both eyes (worse than Big “E” on eye chart), no end stage glaucoma or retinal disease.
The AlphaCor is made of a plastic-type material known as pHEMA and includes a transparent central core with low water content and a cloudy outer porous skirt with high water content as seen below.
The procedure is performed in two stages typically performed three months apart. The first stage uses a 180 degree incision to place the implant within the central portion of the diseased cornea and the outer conjunctiva is placed over the implant to allow for healing (Figure 1). The outer half of the cornea is removed three months later to clear the view into the eye (Figure 2).
Figure 1 Figure 2
The Boston Keratoprosthesis, also sometimes referred to as the Dohlman KPro, uses a central plastic-like material used in old hard contacts, known as PMMA with a surrounding human donor corneal skirt. The advantage of this procedure is its similarity to a traditional cornea transplant procedure with only one stage. Thus, if the rest of the eye is healthy, vision will return more rapidly than with AlphaCor.
KPro assembly uses a central front collar button made of PMMA and a back plate with porous holes which sandwich the inner human cornea.
The donor cornea
is placed on the
front collar
button
A titanium screw
locks the KPro
device into proper
alignment.
While the artificial cornea can restore sight to the blind without rejection, concern for potential complications still include infection, melting of the device, hemorrhage during surgery, worsening glaucoma, and potential for poor vision return if the retina and optic nerve are unhealthy. Risks of this procedure are otherwise similar as with cornea transplantation. Human donor corneal tissue is always preferred over artificial devices; however, artificial corneas can help restore sight to some patients with corneal blindness as seen below.
Patients with the artificial cornea wear a therapeutic bandage lens and administer topical antibiotics indefinitely to lower the risk of the above potential complications.
W. Barry Lee, MD, FACS
W. Barry Lee, MD, FACS
W. Barry Lee, MD, FACS
W. Barry Lee, MD, FACS
W. Barry Lee, MD, FACS
W. Barry Lee, MD, FACS
Typical Eye Prior to KPro
W. Barry Lee, MD, FACS
A hole is punched in the center of the donor cornea