The Boston keratoprosthesis (KPro) is a special plastic device that is used to replace a sick cornea (transparent part of the eye, in front of the iris) in order to restore vision in patients who have failed traditional corneal transplants or have a very poor prognosis of success.
Glaucoma is a chronic disease which causes optic nerve damage secondary to high pressure inside the eye and could lead to vision loss in the long term. Glaucoma is highly prevalent in patients who require a KPro and even more after their procedure.
In order to decrease the intra-ocular pressure, surgeons can use multiple eyedrops. Unfortunately, following the KPro surgery, eyedrops lose their efficiency because they are less absorbed by the eye.
The transscleral cyclophotocoagulation (TS-CPC) is a laser treatment used in advanced refractory glaucoma. This laser helps decrease the intra-ocular pressure and have a better control of the disease. There are different methods of laser transmission, including the continuous transmission (G-Probe) and the micro-pulsation method (Micopulse). Given the high prevalence of glaucoma in patients receiving a KPro, the investigators are studying the effect of giving the TS-CPC treatment prophylactically to patients before their Boston keratoprosthesis.
Our hypothesis is that prophylactic TS-CPC will decrease glaucoma progression as well as the risks of developing glaucoma following the Boston keratoprosthesis .
METHOD The investigators aim to recruit twenty (20) patients who are scheduled to receive Boston KPro. Participants will be randomized into two groups: 1) Groupe 1 will receive a prophylactic treatment of transscleral cyclophotocoagulation a G-Probe. 2) Groupe 2 will receive a prophylactic treatment of transscleral cyclophotocoagulation with a micropulse transmission (MicroPulse). The patients will receive their laser treatment by a glaucoma specialist 4 to 8 weeks before their KPro surgery. One week following their laser treatment, the participants will be examined by their glaucoma specialist.
Following their KPro surgery, patients will have a follow-up at day-1, weeks 1 and 2, months 1 and 3, then every 4 to 6 months for 5 years. Additional non-invasive glaucoma tests will be performed twice during the first 3 months following the surgery and will be repeated every 4-6 months. Visual acuity results, the visual field tests and rates of post-operative complications will be compared between the different groups.
Adults patients
Able to give an informed consent
Capable of being followed during the study
Candidate for the Boston keratoprosthesis type I
Patients younger than 18 years old or older than 80 years old
Unable to give an informed consent
Participating to another interventional glaucoma study
Patients who received a glaucoma surgery or procedure (glaucoma drainage device or TS-CPC treatment) 3 months before their initial visit.
Parallel
Transscleral cyclphophotocoagulation using the Micropulse system ( IRIDEX IQ810 Laser systems, Mountain View, CA).
Procedure/SurgeryTreatment will be applied over the limbal area to treat the ciliary body. The treatment will be delivered with an energy of 2000mW, a cycle of 31,33% and an on/off time of 0,5ms and 1,1ms. It will be delivered around a 360° surface with avoidance of the 3 and 9 o'clock areas. The treatment will be delivered during 80 secondes in each hemisphere and will be repeated twice, for a total of 320 secondes.
G-Probe transscleral cyclphophotocoagulation (Iris Medical Instruments, Montain View, CA)
Procedure/SurgeryTreatment will be applied over the limbal area to treat the ciliary body. Sixteen (16) shots in total, which is four (4) shorts per quadrants, will be transmitted with a power from 1750 to 2000mV (titrating according to an audible "pop") for a length of 2,0 secondes per shots. Treatment will be delivered around a 360° surface and avoiding the 3 and 9 o'clock areas.
Cup-to-disc ratio
Rate of progression of the optic nerve cup-to-disc ratio
No light perception
Rate of patients with no light perception
Need of additional glaucoma intervention
Number of patients requiring any additional glaucoma surgery or procedure ( glaucoma drainage device, transscleral cyclophotocoagulation treatment etc.)
Goldman visual field loss of 30% or more.
Number of patients who lose more than 30% or more of their Goldman visual field during their follow-up. The first first two visual fields will be used at baseline as a baseline reference for comparaison.
Retinal Nerve Fiber Layer thinning
Percentage of patients with Retinal Nerve Fiber Layer thinning on Optical Coherence Tomography.
Complications related to transscleral cyclophotocoagulation treatment
Rate of known complications of transscleral cyclophotocoagulation treatment (hypotony, phthisis bulbi)
Complications related to the Boston keratoprosthesis
Rate of known complications of the Boston keratoprosthesis (corneal melt, retroprosthetic membrane, retinal or choroid detachment)
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Centre hospitalier de l'Université de Montréal (CHUM)
Lead sponsor
Fonds de recherche en ophtalmologie de l'Université de Montréal
Collaborator
