Endoscopic Assisted Anterior Hyaloid Peeling in Boston Type 1 Keratoprosthesis (KPro-HP-Endo)

Boston keratoprosthesis type 1 (KPro) surgery is the most common corneal graft and is used to restore vision in patients with high risk of failure with traditional penetrating keratoplasty. Common complications of KPro surgery include retroprosthetic membrane formation behind the backplate of the KPro. Glaucoma is the most common threat to vision rehabilitation in patients with KPro. Glaucoma is often present before surgery and progresses after KPro, seven times faster than in patients with only glaucoma. Retinal detachment is a common posterior segment complication that arises post-KPro and can lead to a serious loss of vision. Pars plana vitrectomy (PPV) is the standard treatment for patients with vitreoretinal diseases and opacities. PPV can include peeling of the anterior hyaloid membrane to ensure total resection of the vitreous body. PPV allows for example for retroprosthetic membrane excision, installation or revision of a glaucoma drainage device, or repair of retinal detachment. Often PPV is performed at the same time as KPro surgery for different indications. It has been shown to reduce postoperative complications in comparison to when it is performed after the KPro surgery. Patients who receive a complete PPV with peeling of the anterior hyaloid membrane have a lower incidence of retroprosthetic membrane formation and less vision loss due to glaucoma when compared to patients with partial PPV or anterior vitrectomy. Combined surgeries of KPro and PPV offer a complete evaluation of the optic nerve and of the retina, which would not be possible otherwise. During a complete PPV, peeling of the anterior hyaloid membrane is a difficult step because visualisation is poor, especially with a KPro in place. Visualisation can be improved using endoscopy to visualize the inside of the eye over 360 degrees. The investigators suggest that peeling of the anterior hyaloid membrane assisted by endoscopy during KPro surgery would decrease postoperative complications in comparison to a PPV done after KPro surgery and without endoscopy.