Keratoprosthesis is an artificial cornea. It is not affected by environmental conditions, and therefore, it may function for a long term.
First of all, it is carried out for blind patients, who are not eligible for corneal transplantation or who could not benefit from the transplantation despite several attempts. For this reason, it is important for good canditate. It can restore the eyesight – just like a miracle. In our previous practices, high accuracy of eyesight was obtained in a patient, who was blind for 30 years, excluding minimal light perception. If the condition of the eye is appropriate in technical terms, 100% eyesight is even possible. However, the preoparative tests should verify that the posterior chamber of the eye, where vitreus, retina and optic nerve are present, should be intact.
Indications for the keratoprosthesis are diseases of skin and ocular surfaces, such as corneal burns, Steven Johnson Syndrome or Pemphigoid, failure of multiple previous corneal transplantations due to a reason whatsoever, and congenital corneal opacities associated with childhood corneal disability. (such as Peter's Syndrome or Congenital Endothelial Dystrophy)
The success rate is about 60 to 70%. Depending the disease, this success rate changes. Therefore, a variety of keratoprosthesis have been designed, with varying success rates.
Furthermore, the treating doctor should have been trained on this procedure. Special surgery techniques are required. Patients should be followed up well. The procedure poses numerous risks and difficulties. Therefore, patients should be closely monitored in the rest of the life, and additional surgical interventions should be carried out in a timely manner.
The prosthesis is placed into a different cornea by a special technique. Next, the prosthetic cornea is transplanted. Meanwhile, a surgery is carried out for glaucoma – increased intraocular pressure-, native lens is extracted and an intraocular lens is usually inserted for the cataract surgery, and the damage in the anterior chamber, if any, is repaired. The prosthetic transplant can be changed or repaired with other techniques. Therefore, it is not necessary to remove it immediately.
Since glaucoma is a common comorbidity in such patients, it may be necessary to insert a glaucoma tube, or since the eyes are dry, upper and lower eyelids are approximated to each other (pilar tarsorrhaphy) and an accompanying cataract surgery is often required. Therefore, an experienced surgeon should carry out various surgeries or the condition should be managed by an experienced surgical team.
It is important to know the patient must wear a contact lens continuously that is specifically manufactured, and an eye drop should be used every day.
Although the medicine covers all possibilities, loss of the light perception is not really likely. If interventions are made timely, it is almost impossible to experience such situations. If the prosthesis cannot be held in place, corneal transplantation with no prosthesis will restore the former condition at worst. In other words, loss of light perception or removal of eye will never be necessary unless an intervention delays.
In conclusion, in the keratoprosthesis surgery, it is possible, if required, to manage disorders of iris, glaucoma, cataract, cataract and retinal diseases.
Orkun Muftuoglu, Prof. MD.
Koc University Hospital