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Expert Interview Glaucoma
Recent Developments in Glaucoma Therapy
An Expert Interview with Nils A Loewen
Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, US
Nils A Loewen
Nils A Loewen is an Associate Professor in the Department of Ophthalmology at the University of Pittsburgh. At the UPMC Eye Center, he is
the Director of the Glaucoma and Cataract Service, the Vice Chair, Electronic Health Records, and the Director of the Glaucoma Fellowship.
He has 16 years of experience managing basic science and clinical teams. He has mentored 36 trainees. A comprehensive body of
publications and training systems for glaucoma surgery attest to his passion for education. Clinically, he is specialised in minimally invasive
glaucoma procedures that are bleb-free, and has published extensively on his outcomes. In his basic research, his lab is focused on
bioengineering of the ocular outflow system (National Institutes of Health [NIH] K08EY022737). He spearheaded gene therapy for glaucoma
with lentiviral vectors. His current research is focused on using these tools to reverse-engineer a working outflow tract with stem cells. His
research group has published more than 90 articles, book chapters and patents. He is a reviewer for 17 scientific journals and a member
of the American Glaucoma Society, American Academy of Ophthalmology and the Association for Research in Vision and Ophthalmology.
Keywords MIGS simulator, surgical training, microincisional
glaucoma surgery, irrigation and aspiration,
anterior chamber maintainer, viscoelastic,
learning curve, glaucoma severity index,
Disclosure: Nils A Loewen has received honoraria from
Neomedix for lectures and wet labs. No funding was
received for the publication of this article. This is an
expert interview and as such has not undergone the
journal’s standard peer review process.
Authorship: All named authors meet the International
Committee of Medical Journal Editors (ICMJE) criteria
for authorship of this manuscript, take responsibility
for the integrity of the work as a whole, and have
given final approval to the version to be published.
Open Access: This article is published under the
Creative Commons Attribution Noncommercial License,
which permits any non-commercial use, distribution,
adaptation and reproduction provided the original
author(s) and source are given appropriate credit.
Received: 6 July 2017
Published Online: 21 July 2017
Citation: European Ophthalmic Review,
2017;11(1):19–20 Corresponding Author: Nils A Loewen, 203 Lothrop St,
Pittsburgh, PA 15213, US E: firstname.lastname@example.org
G laucoma is one of the leading causes of visual impairment worldwide. Traditionally,
treatment of glaucoma has involved pharmacologic and laser treatment, until the
disease progresses to a stage that warrants the need for trabeculectomy. In recent
years, microinvasive glaucoma surgery (MIGS) procedures have emerged, creating new options
for those who do not meet the criteria for trabeculectomy. In an expert interview, Nils Loewen
of the University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, discusses the latest
development in MIGS, as well as the new glaucoma severity index developed by his research
team. Finally, he describes his work in locating and modifying the main impediment to outflow in
Q. Could you tell us a little about the ex vivo training model your
research group have used for MIGS?
MIGS is performed in a submillimeter-wide space approximately 200 times smaller than what is
used in epibulbar glaucoma surgery. It is surprisingly difficult to master, even for confident anterior
segment surgeons: one has to avoid injuring the ciliary body band, iris root and cornea and learn
to respect the outer wall of Schlemm’s canal. Any undue outward pressure can ruin the collector
channel openings. This is not trivial, and is similar to cataract surgery, where trainees improve
from a 20% complication rate (capsule rupture) to 2% towards the end of their residency training.
Cataract complications simply look more dramatic when they happen. Until now, MIGS trainees
learned by improving in actual patients, but the use of pig eyes is an inexpensive and effective
alternative, as we have shown in our training system. 1 Trainees can estimate their learning curve
by infusing a dye into the eye afterwards and measuring the extent. The main challenge in
learning MIGS is actually the continuous visualisation of the target structure with a goniolens.
This visualisation and the tactile feedback in pig eyes are very similar to human eyes, even though
pig eyes do not have a single Schlemm’s canal lumen but rather Schlemm’s canal-like segments
hidden behind a thick trabecular meshwork.
Q. How do active irrigation and aspiration affect interior anterior
chamber maintenance and ease of handling in MIGS?
In a recent study, we found that the biggest differences are visualisation and versatility. 2 Until now,
the only system that maintained the anterior chamber actively with an irrigation and aspiration
system was the Trabectome (Neomedix Inc.; Tustin, CA, US), while the other surgical modalities
used a viscoelastic device. MIGS that do not have an active chamber maintenance include
a passive dual blade goniectome that excises the trabecular meshwork (TM) 3 and TM bypass
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