MICS MEETS MIGS
Performing micro-incision cataract surgery (MICS) with minimally invasive glaucoma surgery (MIGS) combines the benefits of both techniques in terms of refractive stability and intraocular pressure (IOP) reduction, said Boris Malyugin MD, PhD, Fyodorov Eye Microsurgery Complex, Moscow, Russia.
“MICS and MIGS is a new trend in combined cataract and glaucoma treatment. The techniques are generally safe and easy to perform. But of course there is a learning curve involved,” Dr Malyugin told the XXXII Congress of the ESCRS in London.
MICS refers to procedures using incisions less than 2.0mm in size to remove the lens with coaxial or biaxial instrumentation with the aim of reducing induced astigmatism to a minimum. The term MIGS refers to a range of techniques, generally ab interno in approach and performed under gonioscopic view, which are designed to create new channels for the outflow of aqueous from the anterior chamber into either Schlemm’s canal or the suprachoroidal space, with minimal trauma to the eye and few complications.
Most of them are associated with the use of the micro shunts inserted into the Schlemm’s canal (for instance iStent) or suprachoroidal space (CyPass), while the others are aimed on opening the trabecular meshwork (Trabectome).
He noted that approximately one out of seven patients undergoing cataract surgery also has glaucoma. Included in their number is a population of patients who are in an early stage of the disease and who maintain good control of their IOP but require many medications to do so. It is those patients for whom the MIGS and MICS combined procedures are best suited.
In several published studies, MIGS techniques combined with phacoemulsification have appeared to achieve significantly greater IOP reduction than was achieved with phacoemulsification alone. As a result, patients who have undergone the two procedures require fewer medications postoperatively.
Apart from the presence of well-controlled glaucoma, the indications and contraindications for MIGS and MICS combined procedures are broadly similar to those of cataract surgery alone. One important additional requirement is that patients need to be cooperative and able to follow the surgeon’s instructions, since the procedures are generally performed under local anaesthesia.
Dr Malyugin noted that the literature is sparse regarding the safety and efficacy of combined MIGS and cataract procedures in pseudoexfoliative patients, as they are generally excluded from the clinical trials involving the MIGS devices.
However, one published study showed that pseudoexfoliative glaucoma patients who underwent treatment with the Trabectome in conjunction with a phacoemulsification procedure had greater reductions in IOP than did patients with primary open-angle glaucoma who underwent the same two procedures.
There is a general consensus that the cataract surgery should be performed before the glaucoma surgery. In addition, clear corneal incisions are preferable so that blood does not go under the gonioscopic lens. Furthermore, the incisions should be placed temporally to make it easier or the patient to turn his head or eye as required for the surgery. The surgical microscope should be tilted at a 30 to 45-degree angle.
Dr Malyugin pointed out that eyes with glaucoma represent a special challenge to the cataract surgeon because they are prone to compromised endothelia, small pupils and loose zonules.
“In spite of all this, by using proper technique and utilising intracameral mydriatics with viscoadaptive OVDs to stabilise the pupil, decreasing fluidic parameters and manipulating the nucleus in the very centre of the anterior chamber, it is possible to safely perform a MICS procedure even in a patient with pseudoexfoliative syndrome and a relatively small pupil,” Dr Malyugin said.
He added that the surgeon should use quick-chop manoeuvres to fragment the nucleus. Irrigation and aspiration is best performed using a bimanual method either with a coaxial handpiece, using the second instrument to expose the equatorial portion of the capsular bag in order to completely evacuate the cortical material or with two biaxial handpieces (one used for irrigation, while the other one for aspiration).
If zonular damage should occur during surgery, the placement of a capsular ring can safely repair zonular defects of up to 90 degrees of the capsular bag’s circumference.
In eyes with small pupils, pupil expander rings (such as Malyugin Ring) are extremely useful. In cases with small pupils associated with loose zonules, pupil-expanding hooks, specifically double-threaded hooks having elongated working elements help in stabilising the capsular bag and reducing the amount of stress placed on the capsular bag. That, in turn, reduces the risk of anterior capsulorhexis radial tears and the vitreous loss that might follow.
Patients undergoing the MIGS/MICS procedures do not require special intraocular lenses (IOLs) or special IOL power calculation formula. However, multifocal IOLs are generally contraindicated in such eyes because of the loss of contrast that will occur with progression of their glaucoma.
Cataract surgeons who are unaccustomed to gonioscopic surgery will need to refresh their knowledge of the anterior chamber’s anatomical landmarks before they start performing MIGS procedures.
The choice of which MIGS technique to use is another consideration, Dr Malyugin said. Those currently available have a relatively low complication rate and a good safety profile, and decrease patients’ dependency on medication. However, they also entail some risk of complications such as hyphema, iridodialysis and iritis.
Boris Malyugin: firstname.lastname@example.org