Abstract
Surgical microscopes are vital tools for ophthalmic surgeons. The recent development of an integrated OCT system for the first time allows to look at tissue features below the surface. Hence, these systems can drastically improve the quality and reduce the risk of surgical interventions. However, current commercial OCT-enhanced ophthalmic surgical microscopes provide only one additional cross sectional view to the standard microscope image and feature a low update rate. To present volumetric data at a high update rate, much faster OCT systems than the ones applied in today’s surgical microscopes need to be developed. We demonstrate live volumetric retinal OCT imaging, which may provide a sufficiently large volume size (330x330x595 Voxel) and high update frequency (24.2 Hz) such that the surgeon may even purely rely on the OCT for certain surgical maneuvers. It represents a major technological step towards the possible application of OCT-only surgical microscopes in the future which would be much more compact thus enabling many additional minimal invasive applications. We show that multi-MHz A-scan rates are essential for such a device. Additionally, advanced phase-based OCT techniques require 3D OCT volumes to be detected with a stable optical phase. These techniques can provide additional functional information of the retina. Up to now, classical OCT was to slow for this, so our system can pave the way to holographic OCT with a traditional confocal flying spot approach. For the first time, we present point scanning volumetric OCT imaging of the posterior eye with up to 191.2 Hz volume rate. We show that this volume rate is high enough to enable a sufficiently stable optical phase to a level, where remaining phase errors can be corrected. Applying advanced post processing concepts for numerical refocusing or computational adaptive optics should be possible in future with such a system.
Highlights
Optical Coherence Tomography (OCT) [1] is a non-invasive imaging modality, which uses usually near-infrared light to create three dimensional images with μm-scale resolution
We present live 4D OCT at 1060 nm with 330x330x595 voxels at 24.2 V/s corresponding to 1.58 GVoxels/s, which sets a new record for live OCT imaging and processing and enables new perspectives towards an OCT-only surgical microscope
Live video rate volumetric OCT imaging of the retina with multi-MHz A-scan rates chapter, we describe in detail our setups by starting with the FDML laser itself
Summary
Optical Coherence Tomography (OCT) [1] is a non-invasive imaging modality, which uses usually near-infrared light to create three dimensional images with μm-scale resolution. 4D-OCT without real-time display (4D-OCT with offline processing) has some applications at the posterior eye, where a short update interval between the individual volumes is required. The two last applications are more demanding, as they compare the phase between multiple volumes, where motion artifacts changing the phase should be avoided and the time interval between the volumes should be short enough to evaluate the dynamics of the process They have been exclusive to full field OCT because it intrinsically features a stable phase within a volume and is capable of high volume rates. We combine our fast MHz FDML laser at 1060nm [24, 50] to create high volume rate OCT images with and without our live processing demonstrated previously at 1300nm. We start with a detailed outline of our setup, we show examples of retinal imaging and discuss the challenges related to these experiments such as eye motion, image processing and the necessity of multi-MHz A-scan rates
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