Purpose:
Polarization sensitive (PS) OCT enables imaging of biological tissues with additional contrast based on their light polarizing properties. This contrast aids diagnosis and quantitative assessment of retinal diseases such as age-related macular degeneration (AMD) and glaucoma. Swept source / Fourier domain OCT enables 3D structural imaging of the retina. The properties of new swept laser light sources enable new PS-OCT imaging schemes which allow for retinal imaging at ultrahigh speed.
Methods:
An ultrahigh speed PS-OCT system was developed based on a swept laser source at 1050nm. The sample was illuminated with two orthogonal polarization states simultaneously using a polarization delay unit in the sample beam path. The orthogonal polarization components for the depth multiplexed signals from the two input states were detected using PS detection. The system operated at 100,000 axial scans per second, up to 5X faster than commercial OCT systems. In vivo PS-OCT imaging was performed in the eyes of healthy human subjects. Further, PS-OCT imaging was performed in a rat model. In addition to conventional OCT images based on reflectivity, PS-OCT images displaying the birefringent or depolarizing tissue properties were computed.
Results:
Ultrahigh speed OCT allows 3D imaging of the retina with dense sampling and reduced motion artifacts. Imaging at 1050nm wavelength enables enhanced penetration in deep structures of the optic nerve, the lamina cribrosa and the sclera. PS-OCT images revealed birefringent structures such as the retinal nerve fiber layer and the sclera, and depolarization in the retinal pigment epithelium. Maps displaying the retinal polarization properties were generated. The imaging results in the rat and human retina were compared quantitatively.
Conclusions:
Ultrahigh speed OCT based on swept laser technology enables rapid 3D imaging of the retina and new schemes for PS-OCT. Imaging and quantification of polarization properties is demonstrated in the human and rat retina. The additional contrast provided by PS-OCT might be beneficial for detection and quantification of disease progression and therapeutic response in small animal models.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • sclera