Transformation and cytotoxicity of iron in siderosis bulbi

Ocular tissues from two enucleated and one trabeculectomized human eyes with siderosis bulbi were studied by electron microscopy. Ferritin particles were demonstrated in various cell types of the three eyes. Other types of iron were not identifiable. The ferritin particles were scattered throughout the cytoplasm, with a few particles in the nucleus and extracellular space. More ferritin particles were seen in tissues near the iron foreign body. The cells which contained numerous ferritin particles also had siderosomes, most of which were thought to be conglomerates of the ferritin particles in the secondary lysosomes. Cells with numerous ferritin particles, particularly in the siderosomes, showed vacuolar degeneration. The present study indicated that in siderosis bulbi, iron released from the iron foreign body is deposited as ferritin scattered throughout the cytoplasm and is sometimes accumulated as siderosomes, in the affinitive cells. In siderosis bulbi, the cells become damaged by the deposition of ferritin in the cytoplasm, especially in the form of siderosomes.