Studies have shown IOP lowering associated with procedure in patients with POAG
The effect appears to be durable for at least 24 months. The Hydrus maintained significant reductions in medications and IOP. More importantly, significantly fewer glaucoma operations were required in the Hydrus arm compared with two iStents arm after 2 years of follow up.
This study suggests that trabecular bypass with 3 clock hours of canal stenting—with its assured access to multiple collector channels within the treated quadrant—decreases pressure compared with trabecular bypass alone, where interaction with collector channels is unpredictable.
I have had excellent results in my patients with the Hydrus Microstent that are in line with the published studies. In my experience using the Hydrus Microstent, this is the most powerful MIGS device that can be placed in patients with mild to moderate glaucoma at the time of cataract surgery.
There are no serious risks or complications associated with the procedure.
At times the stent has not been able to penetrate a thickened heavily pigmented trabecular meshwork. Also at times the iStent inject penetrated through both the inner and outer wall of the Schlemm’s canal and is actually implanted into sclera, reducing its efficacy. This has been confirmed by others with AS-OCT imaging of iStent.5
The Xen subconjunctival stent has been not been fullproof in that the 45 μm small lumen will often get obstructed with subconjunctivally or intraluminally. Intraluminal obstruction cannot be overcome with needling or external revision of the Xen.
As we know, many glaucoma patients, despite intervention may progress to a more advanced disease stage.
Cataract surgery and implanting the Hydrus Microstent at an earlier stage will often serve to preserve the health of the patient’s collector channel and provide benefit from the beginning to the end of the disease. This could result in longer-term eye health.
Having performed over 70 of these procedures in patients with glaucoma, not only can I lower the IOP and dramatically reduce the amount of medications needed, but also improve vision from cataract extraction and refractive lens exchange.
This is currently my initial approach to patients with open-angle and angle-closure glaucoma over the age of 50. This does not apply to persons with other types of secondary glaucoma such a neovascular or uveitic.
In the future, use of Hydrus may not be limited to combination with cataract surgery.
In April 2017, the FDA granted Ivantis clearance to initiate a second IDE trial of the Hydrus Microstent. It was approved in 2018, based on results of the HORIZON trial.
The SUMMIT trial will investigate the Hydrus in more challenging cases and will include 60 patients with advanced glaucoma for whom conventional therapies have proven unsuccessful.
Patients in this trial will undergo standalone glaucoma surgery without combined cataract surgery.
1. Harry A. Quigley, MD; John D. Gottsch, MD; Jonathan Javitt, MD; Kuldev Singh, MD. Relationship between intraocular pressure and primary open angle glaucoma among white and black Americans: The Eye Survey. Arch Ophthalmol. 1991;109:1090-1095.
2. Pfeiffer N, Feijoo JG, Fea AF, et al. A randomized trial of a Schlemm’s canal microstent with phacoemulsification for reducing intraocular pressure in open-angle glaucoma. Ophthalmology. 2015;122:1283-1293.
3. Samuelson TW, Chang DF, Marquis R, Flowers B, Lim KS, Ahmed IIK, Jampel HD, Aung T, Crandall AS, Singh K; HORIZON Investigators. A Schlemm canal microstent for intraocular pressure reduction in primary open-angle glaucoma and cataract: The HORIZON Study. Ophthalmology. 2019;126:29-37.
4. Ahmed IK, Fea A, Au L, Ang RE, Harasymowycz P, Jampel H, Samuelson TW, Chang DF, Rhee DJ; COMPARE Investigators. A prospective randomized trial comparing Hydrus and iStent micro-invasive glaucoma surgery implants for standalone treatment of open-angle glaucoma: The COMPARE Study. Ophthalmology. 2019 Apr 26. pii: S0161-6420(18)31710-X. doi: 10.1016/j.ophtha.2019.04.034. [Epub ahead of print]
5. Gillmann K, Bravetti GE, Mermoud A, Mansouri K.A prospective analysis of iStent inject microstent positioning: Schlemm’s canal dilatation and intraocular pressure correlations. J Glaucoma. 2019 May 1. doi: 10.1097/IJG.0000000000001273. [Epub ahead of print]