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Detection and analysis of hard exudates by polarization-sensitive optical coherence tomography in patients with
Jan Lammer1, Matthias Bolz, Bernhard Baumann
1Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.
Purpose:
To image and analyze hard exudates (HEs) and their precursors in patients with diabetic macular edema (DME) by using polarization-sensitive optical coherence tomography (PS-OCT).
Methods:
Twenty-two eyes of 16 patients with DME were imaged by using color fundus photography (CF) and PS-OCT. In PS-OCT, HEs were automatically detected by their distinct polarization-scrambling qualities. Color fundus images were manually graded for the presence of HEs by two masked graders and correlated with the corresponding PS-OCT HE maps: corresponding images were overlaid and an identical grid of 128 × 128 fields was used for correlation of detected HEs.
Results:
In all eyes, HEs were present owing to DME. Agreement of a pixel-to-pixel analysis of HEs in CF images was 0.72 (Cohen's κ) between graders and 0.44 between graders and automated detection by PS-OCT. Mean ± SD detection of HEs was significantly higher in PS-OCT than in manual grading (1180.5 ± 1009.8 fields versus 828.8 ± 695.0 fields; P = 0.02). The higher detection rate of PS-OCT was confirmed by a linear regression analysis with a slope of β = 1.18 (r = 0.81).
Conclusions:
PS-OCT enables not only two-dimensional imaging of the extent of HEs, as in CF, but also allows tissue-specific, three-dimensional imaging of HEs throughout retinal layers, based on their distinct polarization-scrambling characteristics. The higher detection rate in PS-OCT images indicates an increased sensitivity of PS-OCT imaging over conventional CF.
