Purpose: To quantify lipofuscin-associated fundus autofluorescence in patients with pseudoxanthoma elasticum (PXE), a model disease for Bruch's membrane pathology.
Methods: In this prospective, monocenter, cross-sectional case-control study, 49 patients with PXE (mean age: 46 years, range 18-62) underwent quantitative fundus autofluorescence (qAF) imaging with a modified scanning laser ophthalmoscope containing an internal fluorescent reference for normalization of images. The mean qAF values of a circular ring centered on the fovea (qAF8) were measured and compared to 108 healthy controls (mean age 40 years, range 18-64).
Results: Overall, patients with PXE showed lower qAF8 values compared to controls (difference from controls -23%, 95% confidence interval [CI] -29% to -16%, P < 0.001). The reduction was most pronounced in patients older than 40 years (-30%, 95% CI -36% to -23%, P < 0.001) and was negatively correlated with the extent of Bruch's membrane calcification (r = -0.49, 95% CI: -0.67 to -0.22). The topographic distribution revealed a greater reduction of qAF values toward the optic disc than temporally compared to controls (P < 0.001). The phenotype of patients with reduced qAF values was characterized by pattern-dystrophy-like changes (71%; 10 of 14), reticular pseudodrusen (71%; 10 of 14) and limited areas of atrophy (29%, 4 of 14).
Conclusions: Reduced qAF8 values are a characteristic finding in patients with PXE, indicating that Bruch's membrane disease may result in a modification of the accumulation, distribution, or composition (or a combination thereof) of lipofuscin in retinal pigment epithelial cells.