The management of severe anterior segment disease and intractable corneal opacities has evolved rapidly in the recent years. Whereas in the late 1990s there was a push for limbal stem cell transplantation in conjunction with aggressive systemic immunosuppression, the complications and practical difficulties associated with immune therapy have decreased the interest in this technique. Keratoprosthetic devices have been in development for decades. Claes Dohlman, at the Massachusetts Eye and Ear Infirmary, has developed and perfected the Boston keratoprosthetic device. His relentless pursuit of technical improvements of the device has allowed the recent popularization of the Boston keratoprosthesis and its more common utilization in a variety of disorders of the cornea and anterior segment (1).

One may classify vitreoretinal disorders associated with keratoprosthesis implantation into

1. Preexisting vitreoretinal conditions

Keratoprosthesis can be associated with various vitreoretinal disorders that may require vitreous microsurgery (2). The eyes that require keratoprosthetic implantations have commonly been operated on multiple times unsuccessfully and have sustained long-standing inflammation. These eyes may harbor preexisting retinal conditions that may be unmasked by the clear optics of the keratoprosthetic device, such as dense epiretinal membranes, retinal detachment, or macular holes, that may require surgery with the keratoprosthesis in situ.

2. Disorders secondary to the presence of the keratoprosthetic device

Keratoprosthesis can commonly present with retroprosthetic membranes that severely limit visual outcomes. These membranes are usually more frequent and severe in children but can also present in adults. Retroprosthetic membranes are usually too thick and adherent to be amenable to YAG laser and frequently require vitrectomy techniques for removal of the retroprosthetic membrane.

In addition, since the Boston keratoprosthesis never integrates with the host cornea or sclera, there will always be a permanent open wound around the keratoprosthesis that may be the route for bacteria to develop endophthalmitis. The Alphacor keratoprosthesis and the osteo-odontogenic keratoprosthesis designs are attempts to increase integration of the device. Dohlman has noticed that placement of a contact lens over the keratoprosthesis and chronic topical antibiotics decreases endophthalmitis rates.

Glaucoma is very common after keratoprosthesis, and many surgeons recommend primary placement of Ahmed valve glaucoma implants (3). In eyes that have undergone iridectomy, lensectomy, and keratoprosthesis that also have an Ahmed valve, vitreous occlusion of the tip of the Ahmed valve can require emergent vitrectomy for relief of the acute glaucoma attack.

3. Disorders associated with the surgical technique of keratoprosthesis implantation