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    Keratoprosthesis implantation potentially helpful, but tricky

    Important for physicians to manage patients expectations

    A permanent keratoprosthesis (KPro) can help restore the vision of patients with severe corneal disease, but clinicians must watch out for complications, according to Donald J. D’Amico, MD.

    Dr. D’Amico of the Weill Cornell Medical College, New York, described some of those complications in his Pyron Award Lecture during the American Society of Retina Specialists 2016 Annual Meeting.

    The “permanent KPro is increasingly used in ophthalmology and if you haven’t seen patients with a KPro, you soon will,” he said.

    KPros are typically used in patients whose corneal transplants have failed, in patients with chemical burns, and in Stevens-Johnson Syndrome, he said. “It compares favorably to repeat biologic penetrating keratoplasty in many eyes, even after a single failed corneal transplant,” he added.

    He focused on the Boston KPro, which he referred to as the Dohlman KPro in deference to its original designer, Claes Dohlman, MD, PhD.

    Two versions

    There are two types of Boston KPro. Type 1 consists of a plastic front and back plates with a donut of donor corneal tissue sandwiched between them, and a locking ring to hold it together.

    The type 2 Boston KPro, designed for severe, end-stage ocular surface disorders, is similar to the type 1 device but requires a permanent tarsorrhaphy to be performed through which a small anterior nub of the type 2 model protrudes.

    Recent models have featured a titanium back plate intended to enhance biointegration. Since some patients don’t like the way the titanium looks, so experiments are underway to dye the titanium a more natural color.

    Successful implantation begins with a careful history and detailed exam with ultrasound, and it is helpful to look at the optic nerve to see whether it is cupped out, said Dr. D’Amico. A wide-field camera provides a good view, he added, and should be used routinely to examine the fundus.

    In patients with uncertain visual potential, Dr. D’Amico and his team will often perform a brief exploratory surgery and endoscopy in a separate sitting to see if it is worth going forward with a KPro subsequently.

    Retro KPro membrane is opened with a bent needle during vitrectomy. Image courtesy of Donald J. D'Amico, MDIf the patient has decided to have a KPro implanted, it is important to manage the patient’s expectations. “Counsel patients that they will need contact lens and drops lifelong or as long as the KPro is in place,” he recommended.

    At Weill Cornell, Dr. D’Amico and his colleagues prefer to place a KPro in an aphakic patient rather than in a pseudophakic one. They perform a full pars plana vitrectomy at the time of implantation, routinely 25-gauge. They enter 4.5 mm to 7 mm from the center of the device, and always examine the posterior segment carefully while the eye is open prior to KPro placement.

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