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This ensures that the Boston KPro achieves uniform centration with the donor corneal disc. Optical functional properties of the Boston keratoprosthesis.

A device I helped design, the John Centration Ring (ASICO), is helpful in centering the central 3-mm trephination on the donor corneal disc. Current concepts and techniques in keratoprosthesis.

Other types of keratoprostheses of interest include: Alpha Cor artificial cornea; osteo-odonto keratoprosthesis (OOKP); The Alpha Cor was FDA approved in 2002, while the rest aren’t approved in the United States.

The BKPro consists of model types I and II, the former being used in patients with adequate tear function and the latter being used in ocular conditions with no surface tears and the presence of a keratinized ocular surface, where the device is placed through the eyelids to provide vision in an otherwise functionally blind eye.

Once the Boston KPro and the donor cornea areput together in one assembly, the surgeon attaches the entire unit to the patient’s cornea, which has been trephinated to full-thickness in a manner similar to conventional penetrating keratoplasty.

There are two types of backplate attachments: the newer click-on type that clicks onto the optic of the front plate and is made of titanium; and the older snap-on type of backplate that snaps onto the optic and is further secured with a locking ring.

The device has a collar-button configuration; the two main parts of the BKPro are the front plate with its integral optical cylinder or optical stem (3.35-mm diameter) that’s made of poly(methyl methacrylate), and the backplate that can be either PMMA or titanium.

The recent introduction of an enlarged titanium backplate to clamp the donor-host junction is aimed at decreasing the rate of RPM.

However, one should consider the potential postoperative challenges with BKPro, namely possible retro-prosthetic membranes (RPM) (), glaucoma and BKPro extrusion.

The clinical indications for a keratoprosthetic device such as the BKpro include refractory corneal blindness with very poor prognosis for conventional penetrating keratoplasty, such as failed corneal grafts, autoimmune ocular disorders such as Stevens-Johnson syndrome, toxic epidermal necrolysis, herpetic keratitis, congenital anomalies such as aniridia; chemical or thermal injury and pediatric corneal opacities.

Patients who have a high risk of failure with conventional penetrating keratoplasty, and therefore might require an artificial cornea, fall into two categories: those with optimal tear function and those who don’t have lubricating tears and therefore run the risk of surface keratinization and corneal blindness.