Abstract
Purpose: :
To evaluate the different features of the macular disease with polarimetry images.
Methods: :
We prospectively examined cases with central serous chorioretinopathy, epiretinal membrane, early cases of age related macular degeneration, Vogt-Koyanagi-Harada disease, and malignant melanoma. Polarimetry images were digitized using a GDx-N (Laser diagnostic technologies), with scanning polarized light at 780 nm. We computed 18 different image types According to polarizeation content, to probe different features of macular diseases. The image types were as follows: 1.Depolarized light image, 2. Maximum of the crossed detector, 3. Birefringence image, 4. Ratio of the crossed detector, 5. Minimum of the parallel detector, 6. Maximum of the parallel detector, 7.Modulation of the parallel detector, 8. Ratio of the parallel detector, 9. Mean Parallel Polarized, 10. Mean Modulation of the Crossed, 11. Average reflectance image, 12. Ratio Depolarized [ 2 x min( crossed ) ] / [ Mean_Parallel_Polarized + mean(crossed )], 13. Mean of the Crossed Polarizer, 14. Mean of the Parallel Polarizer, 15. mean( parallel ) - modulation( parallel ), 16. mean( crossed ) + mean( parallel ) - mod( parallel ), 17. Phase retardation map 1(Crossed Detector Phase Plot), 18.Phase retardation map (Parallel Detector Phase Plot)Our new metric, the ratio depolarized light image, is designed to emphasize light scatter due to structural changes, because it divides out the index of refraction changes that cause more light return at a given location regardless of polarization content. This is of particular interest in diseases with lesions deep to the retina that may be masked by the overlying bright retinal layers.
Results: :
In both the depolarized light images and the ratio depolarized images, deeper retinal lesions were particularly well-visualized. These results demonstrated the interaction of light and tissue in patients with a new image type, the ratio depolarized images, as well as in diseases with potential changes deep to the retina and not studied previously with this type of technique: Vogt-Koyanagi-Harada and malignant melanoma.
Conclusions: :
Polarization sensitive imaging is an effective tool as a non-invasive assessment of macular disease.
Keywords: image processing • macula/fovea • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)