الفهرس 
STRUCTURE OF THE CORNEAOnly 14 pages are availabe for public view
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Abstract
Cadaveric corneal transplantation is generally successful for restoring vision in corneal blindness. However, there are corneally blind patients who are not suitable for ordinary penetrating keratoplasty. These patients either have severe dry eyes or keratinized ocular surface with altered limbal stem cells, as in cases of: chemical burns, ocular cicatricial pemphigoid, Steven Johnson’s syndrome, keratoconjunctivitis sicca, and multiple graft rejections.
Keratoprosthesis is the only answer for corneal blindness that can’t be treated with keratoplasty. Keratoprosthesis surgery is a surgical procedure by which an artificial cornea is introduced through the diseased cornea.
There are different types of keratoprostheses which have been developing and improving since 1789. Keratoprosthesis devices differ in materials, designs, and technique of application, in a trial to improve the efficacy and the benefit of keratoprosthesis surgery.
Boston keratoprosthesis is fixed to a corneal graft, and then the prosthesis-graft combination is sutured to the host’s cornea.
This type of surgery requires more or less a healthy tearing to preserve the health of the corneal graft, it can be used in chemical burns, early stages of ocular cicatricial pemphigoid, Steven-Johnson syndrome, as there is still sufficient tearing and a considerable corneal bed in the early stages of these diseases. But it is not suitable in cases of repeated graft failure as the body is already synthetized with antibodies that will result into graft rejection, corneal melting and extrusion of the keratoprosthesis.
AlphaCor keratoprosthesis (a soft prosthesis) is inserted inside the host’s cornea. This requires good corneal thickness as its application includes intralamellar dissection. This type of surgery can be used in cases of repeated graft failure, mild-moderate chemical burn, severe dry eye, where the corneal thickness is enough to allow proper application.
Osteo-odonto keratoprosthesis is a prosthesis where a tooth root is used in its manufacture and fixed to the host’s cornea. It can be used in end stage of ocular cicatricial pemphigoid, Steven-Johnson syndrome, severe chemical burns, or repeated graft failure, based on; It is a true autograft (likely will not be rejected), it doesn’t depend on corneal thickness. But being a heroic procedure, requiring highly technical and surgical skills of both dentists and ophthalmologists, it can be postponed as a last option for these patients if other designs failed, and this is; in a trial to avoid many systemic complications associated with OOKP other than the ocular complications in these fragile patients. Also it is not preferred in children to avoid facial asymmetry. In children, Boston keratoprosthesis has the best results in comparison with other types
Till now, it seems that there is no truly ideal keratoprosthesis that can suit all patients who are indicated for the keratoprosthesis surgery. But the surgeon still can choose from the available designs the most appropriate one for every specific patient regarding the following:
-The underlying pathology resulting in the corneal opacity, the age of the patient, the central and the peripheral corneal thickness and the tearing function of the eye.
Keratoprosthesis with better biocompatibility, better fixation techniques, and better long term stability have to develop in the future, as the difference the procedure can make in the lives of those patients is the difference between being immobile to being mobile.