Advances in surgical procedures are opening up new opportunities to treat glaucoma, according to Iqbal Ike K. Ahmed, MD.
"We're really in a renaissance of surgical procedures," said Dr. Ahmed, medical director, Prism Eye Institute, and associate professor of ophthalmology, University of Toronto.
He gave an overview of glaucoma surgery options at the Glaucoma 360 22nd annual glaucoma CME program.
Until now, surgery has been considered a second-line treatment after medication and lasers because of the risks associated with trabeculectomy and tube shunts.
Now ophthalmologists can draw from a larger surgical tool chest. Dr. Ahmed divided these into internal microinvasive glaucoma surgery (MIGS), blebless ab-externo, bleb-forming with or without mitomycin c, and cycloablative.
"How do we get through all the options and where they may fit?" he asked. "For many of these options the data are limited."
He devoted the largest part of his talk to MIGS, which he subdivided into internal and external categories. He included in the talk some devices which have not yet received approval from the FDA.
He further divided the internal MIGS by their outflow targets. Those targeting Schlemm's canal include the Glaukos iStent and iStent inject, the Ivantis Hydrus Microstent, viscodilation, and gonioscopy-assisted transluminal trabeculotomy (GATT).
They are extremely safe, but require technical skill and their ability to lower IOP is limited by episcleral venous pressure, Dr. Ahmed said. These MIGS are currently used in combination with cataract surgery.
The outflow target of the Alcon CyPass Micro-Stent and the Glaukos iStent Supra is the supraciliary space. These benefit from a large potential space and are technically intuitive, said Dr. Ahmed. Their effectiveness varies depending on healing. Their IOP results are also modest, and they are also used in combination with cataract surgery.
Into the category of external MIGS, Dr. Ahmed put the Allergan Xen Gel Stent and the Santen InnFocus MicroShunt, both of which drain through the sclera from the subconjunctival space.
The external MIGS, which create a bleb, have greater probability of hitting target IOP levels without medication; IOP levels with these devices average around 13 mm Hg, said Dr. Ahmed.
The surgeon's choice of procedure depends on the patient's circumstances, Dr. Ahmed said.
"It's very much a matter of balancing out risk reward and effort," he said.
Other factors include the intensity of the postoperative management required, the speed of visual recovery the cost and reimbursement.
The more advanced the glaucoma case, the higher priority becomes the treatment's ability to lower IOP, Dr. Ahmed said. The less advanced the glaucoma, the more important is safety.
"The biggest question I have is whether the patient is controlled at time of presentation," he said.
He ranked procedures for glaucoma according to the levels of IOP they can achieve, from highest to lowest: phacoemulsification, internal MIGS, the external (subconjunctival) MIGS and trabeculectomy.
A patient who tolerates medication and has ocular hypertension or mild-to moderate glaucoma and a target IOP above 15 mm Hg might benefit from glaucoma surgery if cataract surgery created the opportunity, he said.
Patients who have trouble adhering to medication and have an IOP above the target level despite medical treatment could be candidates for laser trabeculoplasty, internal MIGS or subconjunctival MIGS, said Dr. Ahmed.
Those with fast progression might be especially good candidates for subconjunctival MIGS, he said. If the target IOP is very low, patients might go directly to traditional filtering surgery.
Dr. Ahmed is a consultant to Glaukos among many other ophthalmic device and drug companies.