ARVO 2024: How delayed onset of vision impairment alters auditory distance estimation

Ahead of this year’s ARVO meeting, the Eye Care Network team spoke with industry leaders who are scheduled to present at the conference. Ahead of her presentation on Sunday, we spoke with Professor Shahina Pardhan, BSC, PhD, MBCO, H DHealth Brad, who is the Director of the Vision and Eye Research Institute, School of Medicine, at Anglia Ruskin University in Cambridge, United Kingdom.

In this video, Professor Pardhan discusses her presentation, researchers’ misconceptions about the relationship between vision and hearing and the real-life impact of her team’s findings.

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

Hattie Hayes: Hi, my name is Hattie Hayes, and I'm the editor of Ophthalmology Times Europe. This year's ARVO meeting is taking place in Seattle, and we here at the Eye Care Network are speaking to some of the attendees about what they're going to be presenting at the meeting. Joining me today, I have Professor Shahina Pardhan. We are going to be talking about her presentation, which is titled, "Comparison between early onset and late onset vision impairment and age-matched sight controls for auditory distance estimation." Thank you so much for joining me today. I'm really excited to learn more about your presentation and what you have planned for ARVO.

Shahina Pardhan, BSC, PhD, MBCO, H DHealth Brad: Thank you. Good to talk to you, Hattie.

HH: Just to start off, give me a brief overview of what your presentation is about and what people at ARVO could expect to see.

SP: So, the work that we did was to look at how people who've lost their vision estimate the distance of sounds, and estimate the distance of sound sources, in different environments. So this could be environments which have echoes and environments which don't actually have echoes. And what we did was we compared those people who had partial vision loss, and we looked at how their estimation of sounds compared to those who had a late onset of vision loss, and compared that to normal people, too, because this is really quite important. People with vision loss tend to use their auditory performance; they use sounds to navigate safely around the world. They're so much reliant on sound because they've lost their vision. So we wanted to know whether people who had early vision losses faired differently compared to those who had late vision losses, and how both groups actually compared to normal participants.

And what we found was quite interesting, actually. So we found that people who had vision loss estimated distances that were closer, up to about five meters, they estimated these distances to be further away compared to those who didn't have vision loss, so the normal participants. But more importantly, what we did find was those who had vision losses before the age of 10 years, actually estimated these sounds even further away than those who'd lost their vision later on, suggesting that there is something in the brain that hasn't calibrated properly. And they're not actually able to estimate where those sound sources are coming from accurately enough. This has really quite important ramifications. Because if you think about people with vision loss wanting to travel around, and navigate safely in their environments, they actually might think that what they're hearing is further away than they think, so there's quite a lot of safety ramifications on that.

HH: Is there anything that surprised you when you were conducting this research, whether it's an assumption you had about a patient group going in, or whether it's about, you know, the patients' response to the data that you've been collecting? I'm interested to know if there's anything that took you by surprise as a researcher.

SP: The significant difference between the late onset and the early onset group. I was just expecting that to be similar. And it wasn't. So it's almost like, if you've lost your vision earlier, then you can't calibrate to your sound sources, and the distance of sound sources, as long as there is no other reference point to compare with. So there are differences.You are much worse if your vision has got lost earlier compared to if you've lost your vision later. And what was quite surprising was that our data didn't show a difference between late onset and normal participants. And that was, although there was a trend to it, there were no significant differences between the two groups.

HH: What is it like researching this interplay of visual and auditory sciences?

SP: So when I first started, I just assumed that if you've lost your vision, your hearing is going to get better. What we wanted to know was how much has it gotten better? And you know, whether we can model the amount of vision loss to the improvement in your hearing. And therefore we were quite surprised that, in a task where we actually had that discrimination, people who were completely blind were much better. But people who had still some remnants of vision, which is what I call partial vision loss, then they didn't do any better than normal [patients with no vision loss]. So for that particular discrimination task, vision had to be lost completely before hearing got better. And then it actually did get better.

Your hearing performance, when you've lost vision, is very much task-dependent. So if you have, for example, and we've shown this in a laboratory, if you have two sound sources, and you have to discriminate between the distance between those two sound sources, then people who've lost their vision actually do so much better than those who have who have got good vision. So, there are instances and tasks, and perhaps methods, that will show you that...in fact, people who've lost their vision will hear better, because there is what we call sensory substitution in the brain. So part of the brain that was using, or that uses vision to see tends to get used by auditory [procession], by hearing. But only for some tasks, not for everybody, and not for every task.

So there are some tasks, that hearing gets better. And for some tasks, hearing does get worse. In terms of the actual distance of sound sources, which doesn't actually have any reference sound to support it or to discriminate against, we found that, you know, hearing doesn't get better with vision loss. And that vision actually is required for us to calibrate our internal representation of the hearing space that we use. I was quite surprised, because I just assumed that hearing will get better no matter what when vision is lost. And it's really, really quite important because as vision is lost, I mean, hearing is the second most important sense that we have. And although there is some sort of brain activity that does use the part that vision uses when you when you lose your vision, it's not uniform, and it's not uniform for all the tasks. So I was quite surprised about that. And that then enabled us to do a whole lot of different projects on this.

HH: Well, it sounds like there's a lot of surprises, and really fascinating aspects to this research. And I'm curious to know, how do you hope all of these findings will be applied in patients' day-to-day lives? You spoke a little bit to the safety aspect of this earlier, but I'm also just curious to know, how are these new and surprising findings going to translate to to the patient experience?

SP: And that's a really good question, because there's no point doing any research if it's not going to help patients, really. So I think, what we would like to do, based on all the work that we've done and informed by the research that we've done, what I would like to do is train people to recognise and appreciate distances properly, so that they don't start bumping into things, or even worse, think that something coming to them is actually further away than it is. So we can actually look into how we would rehabilitate patients in terms of training them on accurate distance recognition and estimation, so that they know exactly where these sound sources are and be able to navigate themselves around safely in their environments.

HH: What are you most looking forward to at ARVO?

SP: Well, everything actually! Going to the States, I always enjoy going to the States. Looking forward to going to Seattle, meeting up with people, colleagues from all over the world that I haven't seen and we just meet up every year. I've got a whole diary booked now for when I'm meeting friends for dinner. And also, really, it's like a shot in the arm–I really get to know and learn so much from ARVO. So I'm really looking forward to it.

HH: That's wonderful. Take lots of pictures, get some postcards, have a great time. And thank you so much for sharing a little bit of the joy of ARVO with me here today.

SP: Thank you, Hattie.