Cataract surgery is a unique opportunity to treat glaucoma in patients with concomitant disease. Unfortunately, many surgeons miss the opportunity out of fear that combining a glaucoma procedure negatively will impact the refractive results, especially those patients investing in a premium intraocular lens (IOL).
However, in my experience, a well-chosen minimally invasive glaucoma surgery (MIGS) procedure will, at worst, have no effect on the refractive outcomes, and may actually improve outcomes.
When physicians are evaluating glaucoma procedures to combine with cataract surgery, they worry about any procedure impacting a patient’s refraction or astigmatism. The next concern may be how an added glaucoma procedure might burden the physician with additional post-operative care.
Surgeons often fail to consider the risks involved with leaving patients on topical glaucoma drops. Anything that interferes with or irritates the corneal epithelium, such as dryness, will affect the patient’s vision, particularly with multifocal and extended depth of focus (EDOF) IOLs.
Unfortunately, chronic use of glaucoma medications causes epithelial dryness and/or toxicity issues. While glaucoma medications help preserve vision by protecting the optic nerve, many patients experience vision compromised by irritation of the corneal epithelium. If drops can be eliminated or reduced, not only will the glaucoma be better controlled, the patient can experience better vision.
I suggest MIGS for all mild-to-moderate glaucoma patients undergoing cataract surgery, particularly premium IOL patients. Performing a MIGS procedure may be the best, and possibly only, chance to reduce medications and better protect the patient’s eyes with lower intraocular pressure (IOP).
I have the most experience with the iStent trabecular microbypass (Glaukos). The iStent bypasses the trabecular meshwork (TM) by increasing aqueous flow into Schlemm’s canal from the anterior chamber.
The pivotal trial[i] proved its safety and efficacy, and as surgeons have become proficient with the iStent, subsequent trials[ii],[iii],[iv] and a recent meta-analysis[v] have illustrated better long-term results with this procedure when combined with cataract surgery. Additionally, with the iStent, cataract post-operative care protocol remains the same and the surgery schedule remains highly efficient.
Typically, within one to three weeks post procedure, I taper off the glaucoma medications and see how the patient responds. On average, patients experience a 25% lower IOP and decrease medications by at least one drop about 80% of the time.
Pearls for use and insertion
There is a learning curve for this procedure, one that most surgeons are not familiar. The insertion technique needs to be mastered.
First, there is a misconception that this technique causes bleeding. While there may be some reflux, blood in the tube is actually a positive sign, which indicates placement near a collector channel. Blood is rarely present the next day.
In terms of technique, I recommend not over-magnifying. I was taught to utilize high magnification. However, I have found moderate magnification works better as all the landmarks are more visible.
My initial procedures were performed by approaching the TM at a 20º angle, puncturing the TM at this angle, then flattening out the iStent and proceeding to canalize into the TM.
However, I have found it works better to lay the inserter flat against the trabecular meshwork rather than angling at the puncture, as temporal or nasal as possible. I then rotate it centrally, following the curve of the eye wall.
The iStent will naturally burrow into the TM and insert itself easily. This method is dramatically easier in my hands, reducing my frustration as well as that of the OR staff.
Providing premium IOL care
Patients want premium IOLs. They want better vision and they do not want to use drops. Word of mouth is powerful, and patients who hear about a procedure that will reduce or eliminate drops will come.
Physicians need to stay up-to-date, both to remain relevant in today’s world and to provide the best possible care for patients. It is imperative to keep up with the times and changing technology to better serve the patients.
If a surgeon has abandoned the technology because of problems inserting the stent, I recommend working with a successful surgeon on the technique and try again. Both physicians and patients will find it worthwhile.
In today’s environment, not offering a MIGS procedure to a patient who is undergoing cataract surgery is a missed opportunity. In the United States, most MIGS procedures are indicated during cataract surgery.
If that window is missed, surgeons have missed this opportunity to help the patient. Physicians should do all in their power to help patients. Therefore, when implanting an IOL to improve patient vision, surgeons cannot forget to treat the glaucoma as well.
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;118:459-467.
Arriola-Villalobos P, Martínez-de-la-Casa JM, Díaz-Valle D, et al. Combined iStent trabecular micro-bypass stent implantation and phacoemulsification for coexistent open-angle glaucoma and cataract: a long-term study. Br J Ophthalmol. 2012;96(5):645-9.
Fea A. M., Consolandi G., Zola M., et al. Micro-bypass implantation for primary open-angle glaucoma combined with phacoemulsification: 4-year follow-up. Journal of Ophthalmology. 2015;2015:4. doi: 10.1155/2015/795357.795357
Neuhann T. H. Trabecular micro-bypass stent implantation during small-incision cataract surgery for open-angle glaucoma or ocular hypertension: long-term results. Journal of Cataract & Refractive Surgery. 2015;41(12):2664–2671. doi: 10.1016/j.jcrs.2015.06.032.
Malvankar-Mehta M. S., Iordanous Y., Chen Y. N., et al. iStent with phacoemulsification versus phacoemulsification alone for patients with glaucoma and cataract: a meta-analysis. PLoS ONE. 2015;10(7) doi: 10.1371/journal.pone.0131770.e0131770.