AAOpt 2022: The emerging role of biomechanics in glaucoma

Phillip T. Yuhas, OD, PhD, FAAO, assistant professor at The Ohio State University College of Optometry, speaks with Optometry Times®' Kassi Jackson on highlights from his discussion titled, "Stress management: the emerging role of ocular biomechanics in glaucoma," which he presented during the 2022 American Academy of Optometry (AAOpt) annual meeting in San Diego.

Editor's note: This transcript has been edited for clarity.

Jackson:

Hi everyone, I'm Kassi Jackson with Optometry Times, and I'm joined today by Dr. Phillip Yuhas, assistant professor at The Ohio State University College of Optometry. He's here to share highlights from his discussion titled, "Stress management: the emerging role of ocular biomechanics in glaucoma," which he is presenting during the 2022 American Academy of Optometry meeting held this year in San Diego. Thank you for being here. Dr. Yuhas.

Yuhas:

I'm happy [to be here]. Thanks for having me.

Jackson:

Absolutely. So would you please share with us the key takeaways from your presentation?

Yuhas:

Sure. So as clinicians who manage glaucoma, we often think the importance of intraocular pressure. As you all know, intraocular pressure is the leading risk factor for the development and the progression of glaucoma. However, we don't always think about why intraocular pressure is so important.

In glaucoma, of course, high intraocular pressure can press against the optic nerve, damaging the axons of retinal ganglion cells as they pass through the globe and head back towards the optic chiasm. But it's really the structure and the biomechanical parameters of the eye itself that dictate how much of that pressure actually gets passed on to the nerve.

So if you think about intraocular pressure, some patients who have high intraocular pressure never develop glaucoma. On the other hand, other patients who have relatively low intraocular pressure do develop the disease. So what's the difference between those two populations? And emerging evidence suggests that the role of ocular biomechanics—which is defined as the eyes response to an applied force—dictates this difference.

Until recently, we weren't able to measure ocular biomechanics in the clinic, it was purely a research field with little clinical application. However, with the introduction of 2 new noncontact tonometers... we are now able to measure the biomechanical parameters of the eye in the clinic in a very noninvasive manner—with an air puff, essentially. And what studies on this have shown ("this" being ocular biomechanics), is that patients who are unable to dissipate the energy of of high intraocular pressure are more likely to develop glaucoma or to advance in their disease.

The Ocular Response Analyzer has an outcome measure called corneal hysteresis. Again, which measures the eye's ability to dampen forces. So eyes with a high corneal hysteresis are able to dissipate the energy of high intraocular pressure, keeping the optic nerve safe as it leaves the globe and lowering the risk for the development or progression of glaucoma. On the converse, patients with low corneal hysteresis can't dissipate energy and therefore transmit a lot of that energy back to the optic nerve, which can then become damaged in glaucoma.

The Corvis ST is able to measure the stiffness of the eye. And this is very much a new field. There's some evidence that suggests that a stiffer eye is more likely to have glaucoma.; there's other evidence to suggest that a softer eye—a more compliant eye—is at higher risk.

So this is a topic that's just emerging and needs more research done, but it's certainly something that has the potential to influence how we all practice in the upcoming future.

So really, the point of this talk is just to introduce some of those very basic, ocular biomechanical parameters, stiffness, hysteresis, and then to point out that this is an emerging field, there is evidence that this plays a role in glaucoma, and to stay tuned for further developments.

Jackson:

That's great. It sounds like there's a lot of exciting things kind of coming down the pipe with this research. Why is this so important for optometrists to discuss; why do they need to know this?

Yuhas:

That's a great question. So as optometrist, we are often the eye care providers, the doctors who make an initial diagnosis of glaucoma; so being able to have all the information and evidence necessary to make a diagnosis is a critical part of our job, because we don't want to miss patients who do have glaucoma, but we also don't want to diagnose glaucoma patients who don't have the disease. So the more information we can get about the eye, including intraocular pressure, health of the optic nerve, and also corneal biomechanics, as we move forward, will help us to better detect glaucoma and patients who truly have it, and then decide which patients are at lower risk.

Jackson:

Great, and then it's kind of implied, but what does this mean for patient care?

Yuhas:

Well, for patient care, anytime a doctor can have better information in order to make make an accurate diagnosis, the better it is for patients. Again, over diagnosing a disease is just as bad as under diagnosing, especially in glaucoma where a diagnosis of glaucoma often necessitates a lifelong regimen of treatment. And that comes with cost, it comes with lifestyle changes, side effects, the whole thing.

So, the more accurate we can make a diagnosis, the less risk there is of unnecessarily treating. And the earlier we can make a diagnosis of glaucoma, potentially incorporating accurate biomechanical parameters into that decision making process, the sooner we can intervene and prevent vision loss from happening. Because in glaucoma, all treatment is preventative. Once you lose vision in glaucoma, it's gone forever.

So the name of the game—like I tell my patients—is early detection, early management if necessary, and ocular biomechanics have the potential to move that process forward.

Jackson:

Great. there anything we didn't touch on that you'd like to be sure to discuss.

Yuhas:

I just wanted to make people aware that, again, this technology is available now in the clinic and a lot of optometrists who are trained even 10-15 years ago, this wasn't a possibility. So there are all kinds of new technologies coming out. So stay tuned for more on the horizon.

Jackson:

Great. Well, Dr. Yuhas, thank you so much for your time today.

Yuhas:

Thanks for having me.