The lipid composition of drusen, Bruch's membrane, and sclera by hot stagepolarizing light microscopy

PURPOSE. To detect and identify, in situ, the lipid composition of drusen, diffuse Bruch's membrane deposits, and sclera in aging human eyes using hot -stage polarizing microscopy (HSPM), a method that allows qualitative deter mination of lipid subtypes within histologic sections based on morphology a nd melting temperatures of liquid crystals as monitored by birefringence du ring heating and cooling. METHODS. Full-thickness buttons of the central macula and the periphery of human eyes from 17 patients were fixed in 5% calcium-buffered formalin. Fro zen sections were stained with oil red O or Sudan black or were analyzed by HSPM. RESULTS. Birefringent anisotropic droplets ("maltese crosses") with melting characteristics of cholesterol esters were identified within diffuse Bruch 's membrane deposits, drusen, and sclera. Deposits that melted from crystal to oil without any maltese cross formation when cooled were present in the sclera and are consistent with triglyceride-rich deposits. Deposits with o ptical properties consistent with phospholipids were identified in a single aged eye. Eyes from young donors did not show these changes. CONCLUSIONS. HSPM is a valuable technique for evaluating the nature of lipi d deposits in aging eyes. Further studies are warranted to determine whethe r similar changes are also present in eyes with age-related macular degener ation.