Functional retinal imaging

Functional applications of optical coherence tomography (OCT) in ophthalmology are a research focus of AG Hüttmann. The Institute itself and the companies Heidelberg Engineering GmbH, Thorlabs GmbH and Visotec, which cooperate with the AG Hüttmann and have commercialized OCT technologies from our Institute, are developing state-of-the-art OCT technology that enables very fast tomographic imaging of the human retina.

For functional imaging, the smallest changes in the retinal structures are visualized in the nanometer range. This is realized by a phase-sensitive evaluation of the measurement data, in which not only the intensities but also the phases of the complex OCT data are evaluated.

Analysis of the pulsation of retinal vessels

By using extremely fast holoscopy, which was developed by AG Hüttmann in cooperation with Thorlabs GmbH, entire 3D volumes of the retina can be recorded in a phase-locked manner. This makes it possible, for example, to visualize the movement of retinal blood vessels and the surrounding tissue when the pulse wave triggered by the heartbeat hits them. By measuring the pulse wave velocity, biomechanical parameters of the vascular network can be determined non-invasively.

Measuring the reaction of photoreceptors to light

But even much smaller changes can be detected with the help of phase-sensitive holoscopy. In 2015, we succeeded for the very first time in the world in visualizing the visual process in the retina of a living person with spatial resolution. In conventional OCT, imaging errors in the eye prevent individual photoreceptors from being visualized. However, by means of numerical aberration correction, the imaging errors of the eye can be subsequently compensated for in our images so that individual photoreceptors can be resolved. Combined with a phase-sensitive evaluation of the complex OCT data, this makes it possible to directly visualize the reaction of individual photoreceptors to incident light

Reaction of the photoreceptors in a human retina to two different patterns projected into the eye of a test person.