A Pilot Quantitative Study of Topographic Correlation between Reticular Pseudodrusen and the Choroidal Vasculature Using En Face Optical Coherence Tomography

Purpose: To analyze the topographic correlation between reticular pseudodrusen (RPD) visualized on infrared reflectance (IR) and choroidal vasculature using en-face volumetric spectral-domain optical coherence tomography (SD-OCT). Methods: A masked observer marked individual RPD on IR images using ImageJ (NIH, Bethesda, MD). Using the macular volume scan (Cirrus, Carl Zeiss Meditec Inc, Dublin, CA), the RPE slab function was used to generate a C-scan of the most superficial choroidal vasculature. An independent masked grader created a topographic binary map of the choroidal vasculature by thresholding the en-face image, which was overlaid onto the IR map of RPD. For each IR image, ImageJ was used to generate a random set of dots as control lesions''. Results: 17 eyes of 11 patients (78 +/- 13.7 years) with RPD were analyzed. The average number of RPD lesions identified on IR images was 414 +/- 71.5, of which 49.6 +/- 4.3% were located overlying the choroidal vasculature, compared to 45.4 +/- 4.0% in controls (p = 0.014). 50.4 +/- 4.3% of lesions overlay the choroidal stroma, of which 76.5 +/- 3.1% were <= 3 pixels from the choroidal vessels. The percentage of RPD lesions located within <= 3 pixels from the choroidal vasculature was significantly greater than the percentage located >= 7 pixels away. (p<0.0001). Compared to controls (71.6 +/- 3.8%), RPD were more likely to be located <= 3 pixels away from choroidal vessels (p = 0.014). In contrast, control lesions were more likely to be >= 7 pixels away from choroidal vessels than RPD (9.1 +/- 1.9% vs. 4.8 +/- 1.2%, respectively, p = 0.002). Conclusions: Our analysis shows that RPD lesions follow the underlying choroidal vasculature. Approximately half the RPD directly overlay the choroidal vessels and the majority of the remaining lesions were <= 3 pixels (<= 30microns) from the vessel edge, supporting the hypothesis that RPD maybe related to pathologic changes at the choroidal level.