We present a new method for identifying and segmenting the retinal pigment epithelium (RPE) in polarization sensitive optical coherence tomography (PS-OCT) images of the human retina. Contrary to previous, intensity based segmentation algorithms, our method uses an intrinsic tissue property of the RPE: its depolarizing, or polarization scrambling effect on backscattered light. Two different segmentation algorithms are presented and discussed: a simpler algorithm based on retardation data, and a more sophisticated algorithm based on local variations of the polarization state calculated from averaged Stokes vector elements. By using a state of the art spectral domain PS-OCT instrument, we demonstrate the method in healthy and diseased eyes.

PS-OCT represents a powerful tool for increasing image contrast in ocular tissues. The observed polarization-scrambling nature of the RPE may be used in diseased eyes to locate the RPE or remains of the RPE definitively in OCT images.

Licence for PublicationThe Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, an exclusive licence (or non exclusive for government employees) on a worldwide basis to the BMJ Publishing Group Ltd to permit this article (if accepted) to be published in BJO and any other BMJPGL products and sublicences such use and exploit all subsidiary rights, as set out in our licence (http://bjo.bmj.com/ifora/licence.pdf).Competing Interest: None declared. BRVO) were enrolled in the study. Three intravitreal injections of 1 mg bevacizumab (0.04 ml) were administered at 4 week intervals; further retreatment was based on optical coherence tomography (OCT) findings. Follow-up examinations were done at days 1, 7 and 28 and at monthly intervals thereafter. Results: Mean baseline central retinal thickness (CRT) in OCT was 558 µm (range 353 to 928 µm) and mean BCVA was 20/100. One day after the first injection, CRT significantly decreased to 401 µm (p < 0.01). Three injections reduced macular edema to 328 µm CRT (p < 0