Corneal Diseases | Timing of Glaucoma Drainage Device With Boston KPro Surgery

Corneal Diseases research study

What is the primary objective of this study?

Introduction: Boston keratoprosthesis (KPro) is a piece of specialized plastic that replace sick cornea (transparent structure at the front of the eye) in patients who have failed or those who are expected to have poor results with traditional corneal transplantation. While the Kpro can offer dramatic improvement in vision, it is also associated with several complications. Glaucoma (optic nerve damage due to high pressure inside the eye) is one of the most common complications after KPro surgery and can potentially cause irreversible vision loss. The implantation of a glaucoma drainage device (GDD), a tiny tube that drains the liquid inside the eye by bypassing the natural drainage system, is an effective option to lower the eye pressure in patients with KPro. Given the frequency and potentially devastating effects of glaucoma among KPro patients, some surgeons recommend to put in a GDD as a preventative measure. However, there is no consensus on when is the best timing to perform such surgery in relation to the Boston Kpro surgery. Hypothesis: For patients undergoing the Boston KPro surgery, implanting a GDD simultaneously, at the time of surgery, is more efficacious than at 6 months later, in the prevention of the progression of glaucoma and in maintaining better visual functions. Methods: We aim to recruit 40 patients over 4 years. Recruited patients will be randomly assigned to 2 groups: 1) simultaneous GDD implantation at the Boston KPro surgery, and 2) GDD implantation 6 months after the Boston KPro surgery. Once recruited, patients will be followed before the KPro surgery, postoperative day 1, week 1, month 1, 3, 6 and 12. Standard ophthalmological exam will be performed at each visit. Additional non-invasive glaucoma tests and evaluation (visual fields and optic nerve photo) will be performed on day 1, month 1, 3, 6 and 12. For patients assigned to group 2, a GDD will be implanted 6 months after the KPro surgery. They will have additional follow-ups on post-GDD surgery day 1, week 1 and month 1. Results of visual acuity, visual fields, optic nerve evaluation and complications will be compared between the two groups to determine the better timing of GDD implantation.

Who is eligible to participate?

Inclusion Criteria: - Candidate for corneal transplantation due to loss of corneal clarity - Verifiable history of one or more previous full thickness donor corneal transplantation failure - Pre-operative visual acuity of ≤20/80 or worse in the surgical eye - Age ≥18 years - Physical condition suitable for undergoing surgery Exclusion Criteria: - Terminal glaucoma - Terminal retinal diseases

Which medical condition, disease, disorder, syndrome, illness, or injury is researched?

Corneal Diseases

Corneal Opacity

Study Interventions

Interventions can include giving participants drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available or noninvasive approaches such as surveys, education, and interviews.

Device:Boston keratoprosthesis type 1The Boston KPro, purchased from Massachusetts Eye and Ear infirmary (Boston, MA), is implanted using the usual standard technique.

Device:Glaucoma drainage deviceThe GDD that will be used is the Ahmed implant (New World Medical, Rancho Cucamonga, CA). The Ahmed implant will be implanted using the standard technique either at the time of KPro surgery in group 1, or 6 months following KPro in group 2.

Study Arms

Research studies and clinical trials typically have two or more research arms. An arm is a group of people who receive the same treatment in the study.

Simultaneous implantationSimultaneous implantation of a glaucoma drainage device at the time of Boston keratoprosthesis type 1 surgery

Implantation at post-Kpro 6 monthsImplantation of a glaucoma drainage device 6 months after Boston keratoprosthesis type 1 surgery

Study Status


Start Date: March 2014

Completed Date: March 2020

Phase: N/A

Type: Interventional


Primary Outcome: Visual field mean deviation

Secondary Outcome: Disc Damage Likelihood Scale (DDLS) on clinical examination

Study sponsors, principal investigator, and references

Principal Investigator: Mona Harissi-Dagher, MD, FRCSC

Lead Sponsor: Centre hospitalier de l'Université de Montréal (CHUM)

Collaborator: Centre de Recherche du Centre Hospitalier de l'Université de Montréal

More information:

Chew HF, Ayres BD, Hammersmith KM, Rapuano CJ, Laibson PR, Myers JS, Jin YP, Cohen EJ. Boston keratoprosthesis outcomes and complications. Cornea. 2009 Oct;28(9):989-96. doi: 10.1097/ICO.0b013e3181a186dc.

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