Dr Jackie Tan chats with Dr Maria Cabrera about a new technology to seal corneal wounds without stitches.
If you have any questions, comments or suggestions please send them to [email protected]
The Transcript is available in the 'Transcript' tab on this page.
Connect with Dr Jackie Tan:
Email: [email protected]
Don't forget to listen to our previous episodes -->
Ep4: Eye injury registry
Ep3: Herpes Simplex Keratitis
Ep2: Antimicrobial resistance in corneal infections
Ep1: Corneal infection and contact lenses
Connect with us on Twitter:
Dr Maria Cabrera: @CabreraMarie,
Corneal Research Group, Save Sight Institute, University of Sydney: @cornealresearch
Music provided by: Energized morning by Airae
Artwork: made by Freepik from www.flaticon.com
Maria Cabrera (MC): In our last episode, we talked about how an eye injury registry has helped researchers to understand how eye injuries happen to create prevention strategies. We explain that there are two main types of eye injuries: open or closed injuries. As a reminder an open injury is when the eye wall has a full thickness wound, for example a penetrating injury with a sharp object. In this episode, I will chat with Dr Jackie Tanwho will tell us about his project on a new surgical technique to close wounds in the cornea without stitches.
I am Maria Cabrera-Aguas. A Researcher at the University of Sydney, Save Sight Institute. Welcome to the Sydney Eye podcast!
Please consider subscribing to our podcast to receive a notification when a new episode is released. You can find us on Spotify, Apple Podcasts, Google Podcast, Stitcher and on YouTube.
Full-thickness corneal wounds occur with routine cataract surgeries, corneal transplantation, or penetrating injuries. Some complications of a corneal wound are leakage of the anterior chamber fluid resulting in low pressure and deformation of the eye. In addition, ocular surface contaminants can enter the eye’s internal sterile environment, potentially causing an infection in the interior of eye with risk of losing the sight and even the eyeball.
Our guest today is Dr Jackie Tan. He is a General Practitioner based in Adelaide with a passion for vision research and ophthalmology. Currently, Jack is undertaking his PhD under the supervision of Prof Stephanie Watson who is the Head of the Corneal Research Group at the University of Sydney, Save Sight Institute. He is going to share with us part of this project on testing a new technique to close wounds in the cornea without stitches.
MC: Hi Jack. Thanks so much for joining us in our show today.
Jackie Tan (JT): Pleasure.
MC: Jack, I’ve known you for some years now and heard that your project is about a new technique to close corneal wounds without stitches. Can you tell us how this technique works?
JT: Yeah. So it all stands from the fact that corneal sutures are highly skilled dependent, take years to learn and to perfect it, and they're still snaps, you know, they cost a lot of troubles. I suppose we will be using corneal sutures so long we know how well it works and how it wholly works. So we want to have a new technology to circumvent this a difficulty we have in the clinical field. And so well, we investigated this technology, which obviously not not not my I did not invent it, I'm not that smart, but one of our professors came up with this technology and probably part of the team to investigate this technique to overcome sutures in corneal surgery. So that that's my research in a nutshell.
MC: When did you start working on this technique? How many years ago?
JT: Makes me feel like a dinosaur. So I think I started 2015. I'm probably year six. Part time. Of course. I'm still doing a bit of work, clinical work while working on this PhD.
MC: It has been some time. Can you walk me and the listeners through the technique?
JT: Yes, So I think we should go back to if I cannot take the listeners back to basics science of how this technology works. My disclaimer. We haven't used this technology on humans yet, but we use it on several different models. Obviously, hopefully we're moving to humans eventually. So how this technology works. We primarily primarily it’s made of polysaccharide called Chitosan, Chitosan is a repeating monomers of sugar, So other examples of polysaccharides include starch, glycogen, cellulose in the cells’ wall. So it actually is a bio compatible molecule, so you're essentially making all sugar molecules join together to form a rigid structure. So that's Chitosan really, really basic form. With advancements in material science, this Chitosan can be made into a film. This film can be very, very thinly made, almost like a contact lens. You know how contact lens can stick onto the cornea’s surface. So this technology is a bit like that. So it's a tiny little thing, Chitosan film, they can stick onto the cornea surface. Chitosan, in his own, has this hydrostatic attraction to collagen. So it naturally sticks to collagen already. But we can enhance the stickiness of this Chitosan onto the cornea collagen by laser radiation. So that's how the basic science how this technology works. So we make a very, very thin film that sticks into the cornea with laser activation.
MC: Sounds like a very quick procedure…
JT: Yes, Yes, Very, very quick. So far, we have experimented on an eight-millimetre circular patch. So we got a whole round this eight millimetre in diameter and we're also tried a over patch four by six millimetre over shaped patch. We have a laser footprint of about one-millimetre diameter. So the laser beam that we used to so called Colour or shade the patch, that laser that it means footprint about one mm. So we're just gonna move it around the patch onto the whole patches covered, and that varies between 45 seconds to about a minute. So very quick. So considering each cornea’s suture can take you a few minutes. For me, I'm a novice surgeon. Stephanie, my supervisor could do it much quicker, takes me about 2 to 3 minutes at the minimum, one suture. Where's the patch? Let's put it on, laser it before you know it, done, very quick. I mean, this this technique it even being enhanced because at the moment, our laser footprint is one mm. But if the laser footprint can be designed to be bigger essentially put a patch on, you can be that quick, because if you can make beam bigger then this whole thing is covered in with.
MC: Well, indeed it is much quicker than doing some stitches in the cornea. After you laser the patch, what is the next step? Do you need to place a bandage contact lens or anything to protect the eye?
JT: We have at the moment we are seeing very, very strong adhesion onto the cornea surface to a point almost difficult to peel it off, if you want to call it. But it also depends on the native anatomical environment where this patch is deployed. For example, when we did this technology on an enucleated eye with normal eyelids left when you put a patch on, we don't have do anything, we just leave it there. However, with the eyes with an eyelid, we find that sometimes sometimes pushed the film off with the sweeping effect of the eyelids, and sometimes a bandage contact lens could be helpful. We may need to use a contact lens, just to see how things go if things go as well, when they say, look, we may not even need it. Ideally, we don't need it, but we may start with one.
MC: and then what happens with the patch? Is it reabsorbed?
JT: it's biodegradable but it’s quite slow in biodegradation. So I mean, I didn't do the breakdown experiments, but previous researchers have characterised the degradation of these Chitosan films. In lisozymes, lisozymes are found on your tears and that breaks down the Chitosan slowly. So it's a fine balance between how quickly you want the film to dissolve and how quickly you want, how long, you want the film to stay on for healing. So trying to find a balance is can sometimes be quite challenging, and the beauty of this patches that is also semitransparent. It has got a slight tinge, but you can see through it if you really look through it. So you can see whether the wound underneath the patch is healed before you peel it off. At the moment we're seeing weeks before the patch shows any signs of the structural degradation, so it's strong enough to last for weeks, but you can peel off anything you want. If that makes sense.
More on this new technology for closing corneal wounds up next…
But first, have you had any complication from a cataract surgery, corneal transplantation or penetrating eye injury? Tell us your story and email us at [email protected] or share on Twitter with the hashtag sydeyepod, that’s Hashtag S-Y-D-E-Y-E-P-O-D.
MC: Yes, ok, perfect. So, in theory, what would be the advantages of this technique compared to the stitches or to the other and traditional techniques?
JT: So lots of advantages! Sutures because they have to use a needle to pull into tissue and penetrate tissue and bring tissue together, you can cause damage to the surrounding tissue because sutures apply point to point tension on a cornea. The pool can cause unequal tensions caused ? on the surface of the eye, and we call that surgical induced astigmatism. And that's very, very difficult to correct, even with glasses, because these sutures are from materials that could be nylon and silk, they can create a foreign body reaction to the patient.
Then we also have Cyanoacrylate glue, essentially your medical superglue, they are not technically supposed to be using a cornea, but a lot of ophthalmologists are using them off label for saving the eye because when they cannot get anything else, that's like a backup plan, if you want to call it. Cyanoacrylate glue not biodegradable, so they are essentially plastic there are inflammatory because the breakdown product will cause inflammation on the surface of the eye. Cyanoacrylate glue seems very quickly, pretty much instant you know, if you have done any craft accidentally, you touch superglue. So that’s how it works, using the glue on the surface of the eye and it sticks so quickly, which is good. It seals quickly. Trying to be very precisely, those can be a challenge. So combined with the rough surface, inflammatory side effects, are not biodegradable. Cyanoacrylate glue obviously, it's not really approved for ophthalmic use, only uses for a worst-case scenario like a backup plan.
We also got the fibrin glue, which is also quite popular, has been around for 50 years. Fibrin glue is essentially biocompatible and biodegradable, very well tolerated by most patients. It's not uncomfortable but that's the result of a blood-borne virus transmission. Because fibrin glue is derived from blood bank, so depends on what the donor has, obviously was trying to screen it donors. But yes, there is some infection that doesn't get tested or cannot be tested. And there is always a risk of reactivation when you use that.
So that's the traditional techniques. So the advantage is that this technology they are working on has over the over these guys that because most of the glue will seem so far a liquid based so they have to draw it up, put this the liquid onto the wound, and they're forced to set. Ours is completely different. We got to patch, so it's like a band-aid taken to stick onto the eye and you can trigger the stickiness when you already there's actually can put this patch on the eye adjusted onto you. Yeah, this is a perfect orientation, I want this patch to be. And then you put your laser on and he sticks it on. So it gives the operator a lot of control over the adhesion property of our technology and also some of the glue after you put the components on, you gotta wait about half a minute. Sometimes a few minutes. Wait for it to set, especially if it’s fibrin glue. Ours once you put the laser on, it is stuck straight away and because ours is a patch, the size can be adjusted. So if you've got a small wound, you can have a small patch if you got a bigger wound you can make a bigger patch. You got a star shape wound when you can make a bigger patch to cover the star, and this has not yet been tested. But you should have a cornea graft, which is circular big disc. We came to make a little round ring. They go around the wound and that can work. So I think the combination is endless. So that is one of the benefits that we've got.
MC: For sure, this technique is very innovative and tackles several complications from the current corneal wound treatments. Is there any limitation in the size of the wound?
JT: We're hoping that this technology would have unlimited unlimited wound size consideration.
JT: But because this is only early stages of our characterisation, we haven't made them really, really, really big. As a starting point we are only targeting smaller corneal incisions now, so the small ones that we often see in cataract surgery, they usually between two and three mms. That’s perfect target for what we are hoping to use it on. Yes. So if they make sense, I would say we have endless possibilities, but we only starting small.
MC: Okay, all right, so, how far are you and your team to take this technique into the operation room? Because I understand that there is a long process, you have to do different clinical trials and then, how would be your forecast, if everything goes
JT: I have very thankful for the predecessor researchers. They have been and gone before me. And there's so much work. So previous researchers have done in vitro characterisation so in vitro characterisation means that they testing this material in a test tube, making sure it doesn't damage to cells that's been collected from the cornea. So far, there is, or has been, excellent. And then we move on to the cornea, we've done lots of the tensile strength tests not done by myself but by previously researchers, they've done tensile strength testing to see how much strength it takes to split the cornea bits. So, when you come to my turn. I'm actually testing the technology and intact, intact cornea. So, we're using burst pressure now instead of pulling the wound apart. So essentially what I'm doing now, it’s injecting water, fluid if you want to call it, increases pressure in the eye until the eye pops, where we did a cut and seal with the patch. So that's how I'm assessing the integrity of this point. That's what we call ex-vivo testing. So, the answer the question, when are we going to get the humans? I hope soon. But there are some consideration with human ethics committees to see what our investigations are sound worth moving on to a human model.
MC: before we get to the end of this exciting talk, are there any complications from this technique?
JT: Yes. Now we all new technology and new medications is always going to be potential risk. So let me just take you, takes the listeners to a few events, that unexpected event that happened during the course of study. So we've found that, yes, we laser the patch with a handheld laser slowly, but if we accidentally left the laser on one spot for too long, it actually burns the patch. Now what I know it causes any cornea damage, we're not sure, because once is charged, we're moving away and it hasn't really caused, the experiment we did it on eyes they are no live eyes anymore, so we don't know where they were scarring down track. Very important thing is, when you're operating, the laser will be very, very careful. There's also a theoretical risk, because Chitosan is derived from crustacean shells and sometimes with shellfish. So there's that theoretical possibility of patient with seafood allergy, they may not be able to have this technology put on your eyes.
MC: oh wow!
JT: because what about if you reacted that seafood on the cornea, but we do know that the cornea is avascular, that's limited blood supply, but in isometric conditions sometimes they are blood vessels coursing into the cornea. Whether or not you can cause an allergy reaction, we're not sure because we yet have not tested in humans, so it's a theoretical risk at the moment.
MC: Oh wow! Actually, it is a long, it’s a long process but hopefully, we can get it very soon into humans. So if people want to contact you, Jack, what would be the best way to do it? What would be your social media or email
JT: Yeah, I'm supposed to be young, but I'm not very good with social media. I would say best would be go to Save Sight. We have a cornea research group. Leave me a message there or I think my Twitter I think it's @ DrJack10, I think
MC: That’s ok, we can add it into the notes
JT: sorry Maria, not very good with social media. But I would say go to Save Sight, Corneal Research Group, my name should be there and I think there is a link to my email as well.
MC: All right, perfect Jack, no, thank you so much for sharing the project with us today, so we’ll keep in touch to see further advances in this technique
JT: Thank you, Maria. See you around.
MC: Bye, Bye!
In summary, this new technology uses a patch which sticks very strongly to the cornea upon laser activation, sealing full-thickness corneal wounds up to 6 mm in size. Possible applications of this technology include closing leaking, penetrating corneal wounds after routine cataract surgeries, closing traumatic corneal lacerations from battlefield injuries and replacing sutures during corneal transplantations.
I am Maria Cabrera-Aguas, thanks for joining us on the Sydney Eye Podcast. If you haven’t yet subscribed to this podcast you are invited to consider that to receive a notification when a new episode is released.
If you have any questions, comments or suggestions please send them to [email protected] and connect with us on Twitter @CabreraMarie, it’s
C-A-B-R-E-R-A-M-A-R-I-E or @cornealresearch using the hashtag S-Y-D-E-Y-E-P-O-D. Until next time. Bye!