Purpose
Reticular pseudodrusen (RPD), most prominent on infrared reflectance (IR), are a phenotypic finding of age-related macular degeneration (AMD) and a risk factor for increased incidence of progression to late stage AMD. The relationship between RPD and subretinal drusenoid deposits (SDD) has not been systematically evaluated. The goal of this study is to evaluate the quantitative and topographic relationship between RPD on IR and SDD on en-face volumetric spectral-domain optical coherence tomography (SD-OCT).
Methods
RPD were marked on IR images by a masked observer. SDD were visualized on en-face sections of SD-OCT immediately below the external limiting membrane and identified by a semi-automated technique using NIS-Elements Ar (Nikon Instruments Inc., Tokyo, Japan). Control RPD lesions were generated in a random distribution for each IR image using ImageJ (NIH, Bethesda, MD). Binary maps of control and experimental RPD and SDD were merged and topographically and quantitatively analyzed using ImageJ.
Results
54 eyes of 41 patients diagnosed with RPD were included in this study. The average number of RPD lesions on IR images was 320±44.62 compared to 127±26.02 SDD lesions on en-face (P<0.001). The percentage of total SDD lesions overlapping RPD was 2.91±0.87% compared to 1.73±0.68% overlapping control RPD lesions (P<0.05). The percentage of total SDD lesions between 1-3 pixels of the nearest RPD lesion was 5.08±1.40% compared to 3.33±1.07% between 1-3 pixels of the nearest control RPD lesion (P<0.05).
Conclusions
This study identified significantly more RPD lesions on IR compared with SDD lesions on en-face SD-OCT and found that a large majority of SDD (>90% of lesions) were greater than 3 pixels away from the nearest RPD indicating that RPD and SDD are two distinct lesions. The minority of SDD lesions (7.99±2.22%) that were either overlapping or between 1-3 pixels from RPD were more likely to be in that location than predicted by randomly distributed control RPD lesions. Together, our findings indicate that RPD and SDD are two entities that are only occasionally topographically associated, suggesting that at some stage of their development, they could be pathologically related.