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    Single-use MIGS device demonstrates significant reduction in IOP in retrospective study

    Study compared two minimally invasive ab interno trabecular meshwork/canal-based procedures

    Ophthalmic surgeons have long pursued the ideal surgical approach to lowering intraocular pressure (IOP). In the past 5 years, micro-invasive glaucoma surgery (MIGS) has been introduced as an alternative means of improving patient outcomes by facilitating an efficient, effective and safe individualised treatment in the early to moderate stages of glaucoma. 

     

    We now have a host of modern ab interno options available to us, including the following:

    ·       Trabecular bypass procedures that open or facilitate flow through the trabecular meshwork (TM);

    ·       Supraciliary procedures that allow fluid drainage from the anterior chamber into the supraciliary space;

    ·       Transscleral procedures that carry fluid from the anterior chamber to the subconjunctival space, creating a low bleb.

     

    Each have advantages and disadvantages, but there is no doubt that the more options we have available for our patients, the better.

     

    This article reviews data that I presented at the 2017 European Society of Cataract and Refractive Surgeons (ESCRS) meeting in Lisbon, Portugal. It compares two minimally invasive ab interno TM/canal-based procedures; specifically, ab interno trabeculectomy using the Kahook Dual Blade (KDB; New World Medical SA) and implantation of the iStent (Glaukos Corp.).  

     

    It is commonly believed that the juxtacanalicular system is the site of greatest resistance in the conventional aqueous outflow system in most open-angle glaucoma (OAG) patients.1 The goal of canal-based procedures is to remove or bypass the inner wall of Schlemm’s canal to allow aqueous humour more direct access from the anterior chamber to the collector channels along the anterior wall of Schlemm’s canal.

     

    The KDB facilitates ab interno trabeculectomy by employing a single-use, micro-engineered excision blade that makes precise parallel incisions in the TM and inner wall of the Schlemm’s canal to enhance aqueous outflow (Figure 1). 

     

    The blade is introduced into the anterior chamber via a clear corneal incision under gonioscopic view. The tip (a) pierces the TM and the smooth footplate (b) is positioned against the anterior wall of the canal.

     

    The ramp (c) then elevates and stretches the TM, allowing the dual blade (d) to create two parallel incisions as the device is advanced, after which a free strip of TM is fully and cleanly removed through the original incision with minimal residual leaflets.

     

    By removing the desired section of the TM, the device gives aqueous direct access to the collector channels and distal outflow system. The technology is designed to not act upon the scleral wall, which spares the conjunctiva, does not create a bleb, and does not leave a foreign body in the eye.

     

    As with several MIGS devices, use of the KDB requires familiarity with intraoperative gonioscopy. A clear view of the angle is vital, especially as the blade is advanced through the canal. This can be optimised by injecting viscoelastic into the anterior chamber to pressurise the space and deepen the angle surrounding the treatment area.

     

    Proper positioning is also critical: a perpendicular approach to the TM allows for easy accessibility to the angle structures and proper presentation of the dual blades towards the treated TM. Typically, three to six collector channels are exposed with a 3-4 hour treatment using the device.

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