Phacoemulsification Versus Phacoemulsification With Micro-bypass Stent

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.

• iStent implantation (Device): 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.

Primary outcomes

• Change in Intraocular Pressure Between Baseline and 1 Year [1 year]: change in mean unmedicated intraocular pressure between baseline and 1 year

Secondary outcomes

• Change in Glaucoma Medications [1 year]: change in number of topical glaucoma medications at 1 year post operation

Sex: All, ages: 21 Years to 80 Years

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

Participant flow

Outcome results

• Change in Intraocular Pressure Between Baseline and 1 Year (Primary), Mean, mmHg: Phacoemulsification Alone 15 +/- 2.5; Phacoemulsification and iStent 14.7 +/- 3.1
• Change in Glaucoma Medications (Secondary), Mean, number of glaucoma medications: Phacoemulsification Alone 0.75 +/- 1.0; Phacoemulsification and iStent 0.25 +/- 0.68

Adverse events

Time frame: 1 year

Other adverse events by term

• 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. PMID 22814041
• 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. PMID 20202537
• 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. PMID 26147908
• 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. PMID 20828829

• Study Protocol (PDF, 2015-10-06)
• Informed Consent Form (PDF, 2015-10-06)

• Philemon Huang, MMed, FAMS, Principal investigator, National Healthcare Group, Singapore

NIH grants: 2015