Polarization-sensitive adaptive optics enhanced optical coherence tomography with dynamic focus

Abstract

Optical Coherence Tomography (OCT) is an in vivo imaging technique which is able to perform tomographic or crosssectional images of biological tissues. It's main field of application lies in ophthalmology for acquiring 3D volumes of the retina. Thereby unique information about macular diseases such as diabetic retinopathy, or age related macular degeneration can be obtained. However, image contrast may be rather poor in conventional OCT imaging which can be overcome using polarization sensitive OCT (PS-OCT). Another limitation of state of the art is the limited transverse resolution of OCT instruments. The resolution can be improved using adaptive optics. In this thesis an existing adaptive optics-scanning laser ophthalmoscope (AO-SLO) in combination with a time domain OCT (TD-OCT) was upgraded by an additional polarization sensitive channel in order to provide PS-OCT images with cellular resolution. PS-OCT improves the image contrast. Thereby additional information of the retina can be gathered, because several retinal structures (e.g. retinal pigment epithelium) change the polarization state of the light which can be detected using PS-OCT. Furthermore a dynamic focus scheme for achieving isotropic resolution through the whole volume OCT scan was calibrated. To improve the signal-to-noise ratio, the system was partially further developed. The new instrument was tested on technical samples as well as for in vivo retinal imaging. Representative images recorded in healthy volunteers are presented.