A scanning transmission microscopy and eneregy-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 patients dying with AIDS, the incidence of calcium deposits was 14 and 18.6%, respectively, for oxalates and calcium hydroxyapatite. The calcific eyes were examined by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray microanalysis to confirm the elemental nature of the precipitates. Transmission electron microscopy was used in 2 of the cases with oxalosis. Oxalates with a free end exhibited a plate-like shape at SEM and appeared acicular at TEM, due to the reduced thickness of ultrathin sections. Crystals that were embedded in tissues such as the sclera or degenerate detached retinal tissue formed either spherules or plates at SEM. No clear relationship with intracellular structures could be found at TEM, possibly due to postmortem autolysis phenomena. Calcium hydroxyapatite deposits appeared at SEM as fine granules distributed over the collagen fibers of the corneal and conjunctival stroma and the scleral lamellae, but were also present intracellularly, both in the nucleus and cytoplasm of epithelial cells.