Pilot Study of the Topographic Correlation Between Reticular Pseudo-drusen and the Choroidal Vasculature Using En Face Optical Coherence Tomography

Abstract

 

Purpose

 

To study the topographic correlation between reticular pseudo-drusen (RPD) lesions seen on infrared (IR) reflectance and the choroidal vasculature on en face volumetric spectral domain optical coherence tomography (SD-OCT).

 

Methods

 

A total of 17 eyes from 11 patients with RPD were analyzed. We used the macular volume scan (6x6mm cube) reviewed on Cirrus (Carl Zeiss Meditec Inc, Dublin, CA) to study the choroidal vasculature. OCT slab function was used to create a topographic map of the most superficial choroidal vasculature just below the retinal pigment epithelium. ImageJ was used for analysis. RPD lesions were defined as hypo-reflective lesions seen on the registered IR reflectance image and marked by a masked reader. A different masked grader created a topographic binary map of the choroidal vasculature by thresholding the en face slab. Random sets of dots for each IR image were generated and used as control “RPD Lesions” for subsequent analysis. The percentage of RPD lesions located either overlying choroidal vasculature or stroma was compared to the percentage of random dots. Further analysis compared proximity of RPD lesions to the choroidal vasculature in pixels to those of the random dots, as categorized into two groups (1-3 pixels away from vasculature and 7+ pixels). A student t-test with a p-value <0.05 were used in analysis.

 

Results

 

Of the 11 patients, 9 were female, with an average age of 80 years (range: 51-92 years). An average of 50.7% of RPD lesions fell over choroidal stroma (range: 24-69%). Of those lesions, an average of 76.7% fell within 3 pixels away from choroidal vessels (range: 57-93%). Comparing the location of RPD lesions to control, RPD lesions over choroidal vasculature were not statistically different from randomly distributed dots (p = 0.07), while there was a statistically significant difference (p <0.04) for lesions in stroma within 3 pixels of the vasculature.

 

Conclusions

 

Using SD-OCT and registered IR, we found that RPD lesions appear to follow the path of the underlying choroidal vasculature, supporting the hypothesis that RPD are located at the choroidal level. Our data suggests that the majority of RPD lesions lie within 3 pixels from the edge of, but not overlying the choroidal vasculature.

 

 

A: RPD, which appear as hyporeflective lesions (IR), B: Choroid vasculature (c-scan)

 

Keywords: 412 age-related macular degeneration • 688 retina • 452 choroid