Parapapillary drusen of the retinal pigment epithelium

AbstractPurposeTo describe the occurrence, morphology and associations of parapapillary drusen of the retinal pigment epithelium (RPE‐drusen).MethodsUsing light microscopy, we histomorphometrically examined enucleated human eyes.ResultsThe study included 83 eyes (axial length: 25.9 ± 3.2 mm; range: 20.0–35.0 mm). Eyes with parapapillary RPE‐drusen (n = 29 (35%) eyes) as compared to those without drusen had a significantly shorter axial length (24.0 ± 1.8 mm vs 27.0 ± 3.3 mm; p < 0.001), higher prevalence (27/29 vs 12/54; p < 0.001) and longer width (213 ± 125 μm vs 96 ± 282 μm; p < 0.0001) of parapapillary alpha zone, and thicker BM in parapapillary beta zone (8.4 ± 2.7 μm vs 3.9 ± 2.0 μm; p < 0.001) and alpha zone (6.6 ± 3.9 μm vs 4.4 ± 1.5 μm; p = 0.02). Prevalence of parapapillary RPE‐drusen was 27 (69%) out of 39 eyes with alpha zone. Beneath the RPE‐drusen and in total alpha zone, choriocapillaris was open, while it was closed in the central part of parapapillary beta zone. BM thickness was thicker (p = 0.001) in alpha zone than beta zone, where it was thicker (p < 0.001) than in the region outside of alpha/beta zone. BM thickness outside of alpha/beta zone was not correlated with prevalence of parapapillary RPE‐drusen (p = 0.47) or axial length (p = 0.31). RPE cell density was higher in alpha zone than in the region adjacent to alpha zone (22.7 ± 7.3 cells/240 μm vs 18.3 ± 4.1 cells/240 μm; p < 0.001). In the parapapillary RPE‐drusen, RPE cells were connected with a PAS‐positive basal membrane.ConclusionsParapapillary RPE‐drusen as fibrous pseudo‐metaplasia of the RPE were associated with shorter axial length, higher prevalence and larger size of alpha zone, and thicker BM in alpha zone and beta zone. The RPE‐drusen may be helpful to differentiate glaucomatous parapapillary beta zone from myopic beta zone.