Gereon Hüttmann, PhD, introduces holographic OCT to a new audience

Many of the technologies discussed at the International SPECTRALIS Symposium (ISS) in Heidelberg, Germany, feel futuristic. That’s no surprise—after all, the keynote lecture is focused on the use of remote optical coherence tomography (OCT) in outer space. But the innovations discussed at the conference now underway in Heidelberg, Germany, are very real, even if clinicians may not have much experience with them yet.

Gereon Hüttmann, PhD

Gereon Hüttmann, PhD, closed the new technology session with his presentation on holographic OCT, also known as HOLO-OCT. Prof Hüttmann is deputy head of the Institute of Biomedical Optics, University of Lübeck, Germany. In conversation with Ophthalmology Times Europe, he shared details of his presentation and this new technology he’s excited to see in use across the globe.

Ophthalmology Times Europe: You’ll be talking about holographic OCT at the ISS. Can you please give a broad overview of what you’ll be presenting?

Gereon Hüttmann, PhD: OCT uses the phase of the scattered light only for obtaining depth information when recording cross-sectional images. Lateral information is obtained by scanning a focused beam. Due to eye motion and instabilities of the scanning, it is difficult to use the phase for other purposes.

In contrast, in holography, the full phase information is used at one wavelength for imaging surfaces. Holographic OCT combines both and aims to make full use of the phase information in a three-dimensional image of the retina. I will present the technology to achieve holographic tomographic imaging of the retina and show new applications enabled by holographic OCT, including measurement of pulse wave propagation and functional signals in the inner and outer neuronal retina.

OTE: What challenges does HOLO-OCT address, specifically when it comes to functional imaging VS structural imaging of the eye?

GH: The main challenge is currently clinical translation. Currently, we have to use a very expensive camera and suffer from a long duration for the reconstruction of the volumes. A further challenge is higher sensitivity to multiple scattered light. I will present efforts to tackle these problems and discuss the possibilities and limitations to achieve holographic OCT imaging with clinical OCT devices.

OTE: Do clinicians have common misconceptions about holographic OCT? What are the key differences from other imaging technologies, such as optical coherence tomography angiography (OCT-A)?

GH: At the moment, the concept of holographic OCT is largely unknown to clinicians. The aim of my talk is to create awareness for the new options holographic OCT could provide in clinical diagnosis. Holographic OCT is basically an extension of OCT which provides more information, especially on dynamic processes like vessel pulsation, or the response of photoreceptors and neurons to optical stimulation, which enables optical retinography (ORG). OCT-A is already one step in this direction, as it makes vessels visible by the motion of blood cells. Holographic OCT goes far beyond this since it can measure tissue change with higher sensitivity, over larger areas, and over a longer time span.

OTE: In 2023, research on HOLO-OCT from the University of Lübeck won the Heidelberg Xtreme Research Award. What's changed in the HOLO-OCT space in that two-year span?

GH: My group in Lübeck worked basically on clinical translation, completing a first study with 30 healthy subjects and starting soon the next study addressing certain pathologies. Dierck Hillmann, PhD, who won the award and is now working at the Free University of Amsterdam, is extending the concept of holographic OCT to go beyond the limits of resolution currently posed by the limited size of the iris. This will be achieved by diffuse illumination through the sclera. He recently won the ERC Consolidator Grant “FunMicroRetina“ on this topic.

OTE: Your presentation is part of the "new technology" section of the symposium. Which of the other presenters' topics are you most interested in learning more about?

GH: Basically, all the talks are very exciting as they address new options for diagnosis and treatment; we also worked on them in one way or another in our institute. It is very difficult to emphasise one of the topics. If I had to prioritise one, it is "In vivo functional imaging of single retinal ganglion cells with two-photon imaging,” since I was always very sceptical about nonlinear imaging of the retina. I would love to see progress here, since nonlinear imaging could open new avenues.

OTE: Is there anything else in the imaging space which you think deserves more credit or attention?

GH: Well, I think there are currently two frontiers in retinal imaging. One is getting more information from the retina to have better biomarkers for early disease. Here, new imaging technologies and computational imaging play an important role.

The second frontier is to make retinal imaging more available, by having mobile devices at lower cost and the consistent use of AI. For physicists and engineers in biomedical optics, it is very exciting to work on both frontiers and to make the progress in optical technology available for improving healthcare in ophthalmology.