ABiC: A novel approach to ab-externo canaloplasty

TAKE HOME MESSAGE: Ab interno canaloplasty accesses, catheterizes, and viscodilates all sites controlling aqueous outflow. At 6 months, IOP lowering ranges from 33.3% to 38.4%, whether looking at all comers, eyes undergoing simultaneous cataract surgery, those not previously on glaucoma medications, and individuals with and without a history of glaucoma laser trabeculoplasty.

By Cheryl Guttman Krader; Reviewed by Mahmoud A. Khaimi, MD

Oklahoma City, OK-Ab interno canaloplasty (ABiC) is a unique microinvasive glaucoma surgery (MIGS) procedure that is delivering very positive early results, according to Mahmoud A. Khaimi, MD.

Performed in a temporal approach through a 1.8-mm temporal clear corneal incision and using an illuminated microcatheter (iTrack 250A, Ellex) that provides continual trans-scleral visualization, ABiC accesses, catheterizes, and viscodilates all sites controlling aqueous outflow. And, it does so while sparing conjunctiva and without requiring placement of a tensioning suture or leaving device behind.

To date, Dr. Khaimi has performed ABiC in eyes representing a spectrum from early to severe glaucoma. After 6 months of follow-up in 106 eyes with a baseline median IOP of 21 mmHg on 2 medications, IOPs are consistently in the low teens (average decrease ~35%) without any medication, and there have been no significant complications, he noted.

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“ABiC is essentially a foolproof technique because of the live feedback provided using the illuminated microcatheter, and it takes any guesswork out of the efficacy equation because it targets all potential sites of outflow resistance that may be present in the trabecular meshwork, Schlemm’s canal, or collector channels,” said Dr. Khaimi, clinical associate professor of ophthalmology, Dean McGee Eye Institute, University of Oklahoma College of Medicine, Oklahoma City. “In fact, it is the only MIGS procedure to address the collector channels.

“Results from follow-up to 6 months are very encouraging, and we are looking forward to analyzing our 1 year results soon,” he added.

Dr. Khaimi said the idea for ABiC emerged based on his follow-up of patients who underwent ab externo canaloplasty in whom viscodilation was performed only without placing the tensioning suture.. Looking at their outcomes after 3 years, Dr. Khaimi noticed that IOP control remained good, and his observation that 360º viscodilation alone was effective was corroborated by data from Richard Lewis, MD, and other surgeons performing traditional canaloplasty.

Patient selection

Patient selection

Although Dr. Khaimi considers patients on medical therapy for management of mild-to-moderate primary open-angle glaucoma as the primary candidates for ABiC, the procedure is also a suitable option for anyone who has been treated previously with laser trabeculoplasty or patients who are noncompliant with glaucoma medication.

Patients with pseudoexfoliation and pigmentary glaucoma are also candidates, but ABiC is not appropriate for management of neovascular, chronic angle-closure, and angle recession glaucoma.

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In addition, unlike other MIGS procedures that are only approved for use in combination with cataract surgery, ABiC has an indication for use as either a standalone or combination procedure.

“Subgroup analyses using data from my ABiC case series show that the magnitude of IOP lowering achieved is generally similar, ranging from 33.3% to 38.4%, whether looking at all comers, eyes undergoing simultaneous cataract surgery, those who were not previously on glaucoma medications, and individuals with and without a history of glaucoma laser trabeculoplasty,” Dr. Khaimi said.

Mahmoud A. Khaimi, MD

E: mahmoud-khaimi@dmei.org

Dr. Khaimi is a consultant and lecturer for Ellex. He is also clinical investigator for the ABiC procedure.