A scanning transmission microscopy and energy-dispersive X-ray microanalysis of idiopathic ocular calcification and oxalosis in AIDS patients

In a series of 98 consecutive eyeballs enucleated at postmortem from 86 pat ients dying with AIDS, the incidence of calcium deposits was 14 and 18.6%, respectively, for oxalates and calcium hydroxyapatite. The calcific eyes we re examined by scanning electron microscopy (SEM) coupled with energy-dispe rsive X-ray microanalysis to confirm the elemental nature of the precipitat es. Transmission electron microscopy was used in 2 of the cases with oxalos is. Oxalates with a free end exhibited a plate-like shape at SEM and appear ed acicular at TEM, due to the reduced thickness of ultrathin sections. Cry stals that were embedded in tissues such as the sclera or degenerate detach ed retinal tissue formed either spherules or plates at SEM. No clear relati onship with intracellular structures could be found at TEM, possibly due to postmortem autolysis phenomena. Calcium hydroxyapatite deposits appeared a t SEM as fine granules distributed over the collagen fibers of the corneal and conjunctival stroma and the scleral lamellae, but were also present int racellularly, both in the nucleus and cytoplasm of epithelial cells.