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Subspecialties Glaucoma, Glaucoma

Segmented, Pulsatile and Dynamic

At a Glance

  • For the first time, aqueous angiography has been applied to living subjects (both humans and non-human primates)
  • Real-time data from live patients was consistent with previous post-mortem aqueous angiography: outflow is segmentally heterogeneous
  • Furthermore, live-patient data confirmed a pulsatility to outflow and resulted in the discovery of dynamic features of aqueous outflow – a unique observation
  • Increasingly, aqueous angiography appears to have the potential to guide surgery to patient-specific regions, thereby enhancing MIGS outcomes.

Impaired aqueous humor outflow (AHO) is usually associated with resistance in the trabecular outflow pathways – the trabecular meshwork (TM), Schlemm’s canal (SC) and collector channels (CC). So it makes sense (on the face of it) that procedures aiming to bypass or ablate the TM – minimally-invasive glaucoma surgery (MIGS) – are increasingly popular. Big question then: why don’t trabecularly-oriented MIGS procedures drop IOP dramatically in every patient? At least part of the problem may be that AHO is not uniform around the limbal circumference. As some segments have better outflow than others, it’s almost certain that some are better sites for a MIGS procedure than others.

Clearly, we need a tool that allows detailed visualization of the AHO idiosyncrasies in each individual patient, helping us identify sites of outflow resistance. Such a tool would take the guesswork out of the MIGS game, and might permit truly personalized glaucoma surgery. But what would be the key features of such a tool? The ideal tool would be able to provide real-time, physiologically-relevant and comprehensive information from the patient’s eye in situ. In this context, ‘comprehensive information’ would cover structure and function across all trabecular AHO pathways in their entirety: both linearly (from the anterior chamber [AC] to the episcleral vein) and circumferentially (360° of coverage). But how close are we to this ideal?

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About the Author

Alex Huang

Alex Huang is Assistant Professor at the Doheny and Stein Eye Institutes, Department of Ophthalmology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA. Huang is a glaucoma specialist and advanced cataract surgeon who supports all current and minimally invasive glaucoma surgical procedures. Huang carries his interests regarding angle-based approaches and native outflow pathway improvement into the laboratory as a National Institutes of Healthsupported clinician-scientist. His lab explores post-trabecular meshwork outflow resistance as well as real-time aqueous outflow imaging technologies for the development of customized glaucoma surgeries. Huang’s clinical practice emphasizes a balance of modern surgical techniques with traditional approaches to ensure optimal glaucoma management. In 2017, Huang was voted #1 on The Ophthalmologist Rising Stars Power List.


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