Purpose
We hypothesized that depolarization in polarimetry imaging is useful to evaluate the damage to the retinal pigment epithelium (RPE). In this study, we evaluated geographic atrophy in age-related macular degeneration, using polarimetry methods.
Methods
We prospectively examined 15 eyes of 14 patients with geographic atrophy in age-related macular degeneration . Depolarized light images were computed using a scanning laser polarimeter (GDx-N), with scanning polarized light at 780 nm. To obtain polarimetry information with improved axial resolution, we applied a custom-built a fiber-based polarization-sensitive swept-source optical coherence tomography system (PS-SS-OCT: central wavelength: 1040 nm, A-line rate: 100 kHz). We imaged 2 of the 15 eyes using PS-SS-OCT and measured the phase retardation and degree of polarization uniformity (DOPU). Each polarimetry image was compared with autofluorescence (AF) images recorded with confocal scanning laser ophthalmoscope (F-10).
Results
In all eyes, decreases of AF were observed at the atrophic areas. In depolarized light images, these areas could be detected as low-intensity areas, and low-intensity areas in depolarized light images were wider than AF images in 12 of 15 eyes. In PS-SS-OCT, high DOPU (low polarization scramble) at RPE was observed in these areas. In 14 eyes, increases of AF were observed at the junctional areas. These hyper-AF areas showed high-intensities areas in depolarized light images in 5 of 14 eyes. In other eyes, no specific findings in depolarized light images could be detected at hyper-AF areas. In 12 of 15 eyes, depolarized light images showed high-intensity spots at junctional zone, not related with AF findings. These spots were low DOPU (high polarization scramble) masses in the RPE and choroid in PS-SS-OCT images.
Conclusions
Depolarized light image and AF images showed different features in geographic atrophy. Depolarized light images might reflect the abnormalities of melanin, and melanin in RPE might be more widely damaged than AF findings. Polarimetry imaging may assist the non-invasive assessment of geographic atrophy.
Keywords: 412 age-related macular degeneration •
550 imaging/image analysis: clinical •
701 retinal pigment epithelium