Transparency is essential for eyes, which serve as cameras. However, decreased transparency caused by accumulation of abnormal proteins is commonly observed especially in elderly people. However, the mechanism of accumulation of abnormal proteins in various ocular diseases is still unclear. In the present study, we investigated the role of D-amino acids in the development of accumulation of abnormal proteins in age-related ocular diseases. Whole eyes with age-related macular degeneration were excised from four patients. Surgical specimens with pinguecula were excised from eight patients, and specimens with climatic droplet keratopathy were excised from three patients. Polyclonal antibody to the D-beta-Asp-containing peptide was prepared. Using the antibody, immunohistochemical localization of D-beta-Asp-containing proteins was determined. In eyes with age-related macular degeneration, accumulation of abnormal proteins was observed between the retinal pigment epithelial cells and Bruch's membrane. The accumulated abnormal proteins were positive for D-beta-Asp-containing peptides. In surgical specimens with pinguecula and climatic droplet keratopathy, abnormal accumulation of proteins seen in the superficial layer of the stroma was positive for D-beta-Asp-containing peptide. The results indicate that development of D-beta-Asp-containing proteins in vivo have a central role in the development of accumulation of abnormal proteins in age-related macular degeneration, pinguecula, and climatic drop-like dystrophy.