Phacoemulsification Versus Phacoemulsification With Micro-bypass Stent

Phacoemulsification Versus Phacoemulsification With Micro-bypass Stent Implantation in Primary Angle Closure and Primary Angle Closure Glaucoma: Randomized Double-masked Clinical Trial

Assessing the safety and efficacy of a micro-bypass stent in combination with cataract surgery in subjects with primary angle closure. Subjects are randomized into two arms: phacoemulsification cataract surgery alone versus phacoemulsification cataract surgery combined with the micro-bypass stent implantation. Post surgery intraocular eye pressure will be recorded to assess the efficacy of both arms.

Aim: To assess the safety and efficacy of the iStent trabecular micro-bypass stent (Glaukos Corporation, Laguna Hills, CA) in combination with cataract surgery in subjects with primary angle closure and mild to moderate primary angle closure glaucoma Method: Prospective, randomised controlled trial, blinded to patient and intra-ocular pressure measuring staff. 32 patients, 1:1 ratio, in 2 arms of phacoemulsification alone compared to phacoemulsification with iStent. Hypothesis: Phacoemulsification with micro-bypass stent has a better intraocular pressure (IOP) lowering effect compared to phacoemulsification alone in primary angle closure and primary angle closure glaucoma at 1 year after surgery. Importance: Primary angle closure and primary angle closure glaucoma are conventionally treated with eye drops that lower the intraocular pressure (IOP). Phacoemulsification/lens extraction can often help lower the eye pressure by widening the drainage angle and via ultrasound mechanisms, however, in some cases the IOP is not lowered, or even can cause the IOP to be higher. The iStent implant can be used together with phacoemulsification to lower the IOP and in Primary open angle glaucoma, it gives an additional 20% IOP reduction. It is unclear what effect the iStent has in primary angle closure or primary angle closure glaucoma as it has never been studied. It is important because primary angle closure glaucoma is much more common in the Singaporean Chinese population and the iStent can potentially be used to control the IOP instead of conventional eye drops and glaucoma surgery which have their own potential adverse effects. Potential Benefits: iStent with phacoemulsification may control the IOP better than phacoemulsification alone, reduce the need for IOP lowering medication after surgery, and prevent the need for glaucoma surgery in the future. Potential Risks: The iStent has risks of IOP spikes, bleeding in the anterior chamber and iStent dislocation.Phacoemulsification has the risks of: infection, bleeding, reduced vision, inflammation, posterior capsular rupture, vitreous loss, retinal detachment, endophthalmitis, suprachoroidal haemorrhage and Intraocular Lens dislocation.

Single centre, randomised prospective trial, the patient and the intraocular pressure (IOP)checking staff will be blinded. Randomised by random envelope shuffle technique. 1:1 ratio allocation 2 arms: phacoemulsification alone and phacoemulsification and iStent. 16 patients in each arm, 32 patients in total. The post-operative management is the same for both arms After operation the patient will be followed up at day 1, week 1, week 2, months 1, 3, 6 and 12. At each visit the patient will have the following tests: Tonometry (IOP check) - Not to be taken by the operating surgeon, to be taken by 2 people, one IOP checker and one reader.

Shuffled envelope system. Patient will be blinded to the procedure. The intraocular pressure (IOP) measure and reader will be blinded to the procedure. There will be no planned breaking of randomization. Unplanned breaking will happen if any envelopes are damaged or lost. Unmasking will take place after 1 year post operation by the study team to inform the patient of the procedure.

phacoemulsification cataract surgery with intraocular lens implantation combined with iStent implantation

The iStent is a FDA and Health Sciences Authority (HSA) approved micro-bypass stent device that bypasses the trabecular meshwork (filtration membrane of the aqueous fluid exit pathway) and reroutes aqueous from the anterior chamber directly into canal of Schlemm and out of the eye. It lowers the intraocular pressure (IOP) by increasing the outflow of fluid from the eye from the micro-bypass. In angle closure, the lens has to be removed to create enough space for the iStent to be inserted.

Inclusion Criteria: able to provide informed consent Previous diagnosis of Primary Angle Closure or Primary Angle Closure Glaucoma Intraocular Pressure above 21mmHg at 3 separate visits On 1 or more hypotensive medications Pre-operative visual acuity of no better than 6/12 Exclusion Criteria: Other glaucoma diagnosis: Primary Open Angle Glaucoma, secondary glaucoma Peripheral Anterior Synechiae in the nasal and inferior quadrant Cloudy cornea affecting view for iStent implantation Previous glaucoma surgery History of Ocular trauma Ocular surface disease Pre-proliferative or proliferative diabetic retinopathy Age related macular degeneration with macular scar or macular atrophy

Craven ER, Katz LJ, Wells JM, Giamporcaro JE; iStent Study Group. Cataract surgery with trabecular micro-bypass stent implantation in patients with mild-to-moderate open-angle glaucoma and cataract: two-year follow-up. J Cataract Refract Surg. 2012 Aug;38(8):1339-45. doi: 10.1016/j.jcrs.2012.03.025.

Fea AM. Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary open-angle glaucoma: randomized double-masked clinical trial. J Cataract Refract Surg. 2010 Mar;36(3):407-12. doi: 10.1016/j.jcrs.2009.10.031.

Malvankar-Mehta MS, Iordanous Y, Chen YN, Wang WW, Patel SS, Costella J, Hutnik CM. iStent with Phacoemulsification versus Phacoemulsification Alone for Patients with Glaucoma and Cataract: A Meta-Analysis. PLoS One. 2015 Jul 6;10(7):e0131770. doi: 10.1371/journal.pone.0131770. eCollection 2015.

Samuelson TW, Katz LJ, Wells JM, Duh YJ, Giamporcaro JE; US iStent Study Group. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology. 2011 Mar;118(3):459-67. doi: 10.1016/j.ophtha.2010.07.007. Epub 2010 Sep 15.