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Glaucoma: The problem

Dr Coote discuses the medical problem of glaucoma and how 3D printing technology has improved the procedure.
My job is mainly around glaucoma which is a disease of pressure and flow of fluid through the eye. And so some people, not everyone, with glaucoma needs an operation to resolve it. And operations should be efficient, and should be predictable, and should work out the best for the patient. But glaucoma operations are imperfect. And so I spend a fair bit of my time doing the operations in a clinical sense, but also in researching how to make them better. And how to make them work more predictably and with less problems. What we did was we tried to take the approach that engineers and designers do which is to iterate and reiterate our designs.
Our problem though is we couldn’t take something from the shelf and just apply it to our models. The models and things that we had to investigate our glaucoma research were really pretty imperfect. And we had to, in a sense, start from scratch. So the first thing we did was engineer and model all– in an engineering paradigm all– of the things that were happening in terms of glaucoma. That included fluid flow in terms of sort of where the obstructions were occurring, where the absorption of fluid was occurring. We come up with the understanding that the fluid porosity, fluid flow through tissue, was the most important issue. But we didn’t have a way to test that.
So what we then built, as you know, is new implants that we could then test that particular characteristic. And what we’ve been able to do is iterate those rapidly. So the technology that’s now available to us through places like this is that it allows us to get inside problems and change them without necessarily creating an end product, but actually producing flexible research apparatus to understand the problem. I think once we get a deeper understanding of problems, often the solution then arises. But we didn’t have any of these things, and it was very difficult to produce them without 3D printing.
The principal about glaucoma implants is that it takes fluid from the inside of the eye and deposit it via a tube to a plate. And from the plate the fluid is absorbed into the bloodstream. So this is the inside of the eye. The fluid comes up. And then goes into what’s called a capsule– an area where there is increased density of tissue or decreasing permeability. So fluid, if you follow it, is going to exit from here, and go into around the plate, and then try to traverse this area. And from there, it’ll get absorbed. That ring– that red ring of porosity or loss of porosity– we call the capsule.
And managing the porosity across that space is the key to understanding how we’re going to solve the problem. The issue is that fluid actually causes a loss of porosity. Inflammation causes a loss porosity. Some of the sort of positive feedback mechanisms that occur in tissues as they’re stressed also cause a loss of porosity. And there’s no doubt that medication, and managing fluid, and changing the shape of this apparatus, are great ways to interact.
One of things that we’re currently talking about is how we might manage fluid presentation to this particular device at this level, how we might make it safer at this end so that it doesn’t effect the cornea of the eye, and how it might offer drug delivery– or drug pharmaceutical agents– into this space so that they’ll manipulate the process of healing. So currently our glaucoma– experimental glaucoma implant– now has a second tube which then gets attached to a picoliter pump, which is something that is particularly [INAUDIBLE] pressure. Dependent picoliter pump which contested exactly how porous the capsule is. So we’ve got very accurate methods of telling how this all works.
The glaucoma implants has posed us with quite a nice challenge that allows us to test the real capabilities of poly-jet printing. The limitations are in the areas of the internal tubing. We need to have small, controlled features that are 700 microns in diameter, that allow us to reliably place silicone tubes within the implants itself. We base it around a revolve structure. So a small profile that was revolved around an 8.3 millimetre diameter, then incorporated two fluidic pathways and two suture points which allow the clinician to fix the implants in place during procedures.
The problem

An iterative process

Professor Michael Coote, an eye specialist treating glaucoma spends a fair bit of time doing glaucoma operations and researching how to improve the procedure. Dr Coote takes an engineering or designing approach, and iterates and reiterates on his work.
3D modelling technology has improved this iterative process in that it allows researchers to go inside a problem and produce flexible research apparatuses to understand the problem. Previously, this was very difficult to produce without 3D printing.
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