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.