Age-related changes in the morphology, absorption and fluorescence of melanosomes and lipofuscin granules of the retinal pigment epithelium.

The morphological and spectral characteristics of purified populations of melanosomes and lipofuscin granules from the human retinal pigment epithelium (RPE) were studied with respect to donor age. All melanosome and lipofuscin fractions exhibited the typical ultrastructural appearance associated with these granules. Absorption profiles of both melanin and lipofuscin granules demonstrated an increased optical density of the granules with increasing age. The former was associated with an overall increase of melanin within the granules. Melanosomes were weakly fluorescent; emission in the blue decreased with increasing age while emission in the red increased. The fluorescent intensity of lipofuscin granules increased with age. These results provide support for the concept that melanogenesis is occurring within the human RPE throughout life and that pigment granules within the RPE undergo age-related modifications during life.