Julia Hafner

Visualization of micro-capillaries using optical coherence tomography angiography with and without adaptive optics.

The purpose of this work is to investigate the benefits of adaptive optics (AO) technology for optical coherence tomography angiography (OCTA). OCTA has shown great potential in non-invasively enhancing the contrast of vessels and small capillaries. Especially the capability of the technique to visualize capillaries with a lateral extension that is below the transverse resolution of the system opens unique opportunities in diagnosing retinal vascular diseases. However, there are some limitations of this technology such as shadowing and projection artifacts caused by overlying vasculature or the inability to determine the true extension of a vessel. Thus, the evaluation of the vascular structure and density based on OCTA alone can be misleading. In this paper we compare the performance of AO-OCT, AO-OCTA and OCTA for imaging retinal vasculature. The improved transverse resolution and the reduced depth of focus of AO-OCT and AO-OCTA greatly reduce shadowing artifacts allowing for a better differentiation and segmentation of different vasculature layers of the inner retina. The comparison is done on images recorded in healthy volunteers and in diabetic patients with distinct pathologies of the retinal microvasculature.

Multi-modal adaptive optics system including fundus photography and optical coherence tomography for the clinical setting

We present a new compact multi-modal imaging prototype that combines an adaptive optics (AO) fundus camera with AO-optical coherence tomography (OCT) in a single instrument. The prototype allows acquiring AO fundus images with a field of view of 4°x4° and with a frame rate of 10fps. The exposure time of a single image is 10 ms. The short exposure time results in nearly motion artifact-free high resolution images of the retina. The AO-OCT mode allows acquiring volumetric data of the retina at 200kHz A-scan rate with a transverse resolution of ~4 µm and an axial resolution of ~5 µm. OCT imaging is acquired within a field of view of 2°x2° located at the central part of the AO fundus image. Recording of OCT volume data takes 0.8 seconds. The performance of the new system is tested in healthy volunteers and patients with retinal diseases.

Analysis of retinal layer thickness in diabetic macular oedema treated with ranibizumab or triamcinolone

To evaluate detailed changes in retinal layer thickness in spectral‐domain optical coherence tomography (SD‐OCT) images during a 1‐year follow‐up of patients treated for diabetic macula oedema (DME).

Correlation between corneal and retinal neurodegenerative changes and their association with microvascular perfusion in type II diabetes

The pathophysiology of diabetic neurodegeneration and microvasculopathy remains controversial. Neurosensory layer thickness and corneal nerve fibre loss represent potential biomarkers of neuropathy. The purpose of this cross‐sectional study was to determine the correlation between these neurodegenerative features and their association with retinal microvascular integrity in patients with type II diabetes without retinopathy.

Investigation of the benefit of adaptive optics optical coherence tomography angiography for the human retina (Conference Presentation)

In this work we investigate the benefits of using optical coherence tomography angiography (OCTA) in combination with adaptive optics (AO) technology. It has been demonstrated that the contrast of vessels and small capillaries can be greatly enhanced by the use of OCTA. Moreover, small capillaries that are below the transverse resolution of the ophthalmic instrument can be detected. This opens unique opportunities for diagnosing retinal diseases. However, there are some limitations of this technology such as shadowing artifacts caused by overlying vasculature or the inability to determine the true extension of a vessel. Thus, the evaluation of the vascular structure and density can be misleading. To overcome these limitations we applied the OCT angiography technique to images recorded with AO-OCT. Due to the higher collection efficiency of AO-OCT in comparison with standard OCT an increased intensity contrast of vasculature can be seen. Using AO-OCTA the contrast of the vasculature to the surrounding static tissue is further increased. The improved transverse resolution and the reduced depth of focus of the AO-OCT greatly reduce shadowing artifacts allowing for a correct differentiation and segmentation of different vascular layers of the inner retina. The method is investigated in healthy volunteers and in patients with diabetic retinopathy.