Abstract
Purpose: :
To describe the prevalence, distribution, morphology, and relationship of Lipid Wall (LW) and basal linear deposits (BlinD) in eyes with ARM. LW is a densely packed layer of lipoprotein particles rich in esterified and unesterified cholesterol external to the retinal pigment epithelium (RPE) basal lamina in aged human eyes. BlinD is a lipid-rich extracellular lesion, specific to ARM, located at the same plane.
Methods: :
32 donor eyes with grossly visible chorioretinal pathology consistent with ARM were studied (23 women, 9 men, ages 64-97 yr, 9 clinical diagnoses of ARM). Globes were preserved in mixed aldehyde fixative, and then blocks from the macula (fovea and temporal parafovea) and temporal equatorial periphery were post-fixed with osmium- tannic acid- paraphenylenediamine to enhance neutral lipid visualization. Sections (1 µm) of RPE/Bruch’s membrane (BrM) complex examined by light microscopy revealed 24 dry and 8 wet ARM cases. In vertically oriented sections examined by transmission electron microscopy, LW was recognized by 1 or more rows of 60-100 nm electron-dense particles. BlinD was recognized by larger and more irregularly-shaped particles, with or without contents, that were bounded by highly electron-dense membranes (EER, 80:761). Lipid preservation in 90% of blocks was adequate to permit confident evaluation.
Results: :
All eyes with interpretable BrM images showed significant lipid particle accumulation. LW was found in 24 (67%) eyes, including the periphery of 16 eyes (50%). Progressive stages of LW maturation were noted, beginning with a patchy 1-particle-thick layer, a continuous 1-particle thick layer, and multiple-particle-thick layers with an undulating inner surface. Focal areas of membranous material appeared within thicker LW. Of 32 eyes, 14 (44%) had BlinD in the macula, including the periphery of 2 (6%) eyes. Thinner layers of BlinD contained solid particles and membranous vesicles, and thicker layers contained only membranous vesicles.
Conclusions: :
Both LW and BlinD were originally identified in the macula. Our results extend recent findings in a smaller sample (Curr Eye Res, 32:791) that LW occurs in periphery and further indicate that even BlinD also occurs in the periphery. LW occupies the same location as BlinD, and transitional forms between these two aggregations are now discernable. Therefore, LW is an immediate precursor to BlinD.
Keywords: Bruch's membrane • lipids • microscopy: electron microscopy