Hydrogel keratophakia: long-term morphology in the monkey model.

After 8.5 years a rhesus monkey with bilateral hydrogel (Permalens) intracorneal implants was evaluated by light microscopy and transmission electron microscopy to determine the long-term effects of a synthetic plastic upon the primate cornea. Light microscopy revealed that the hydrogel lenticules were implanted between 80 and 90% of stromal depth, causing posterior bulging of the stroma into the anterior chamber; this was also seen clinically with slit-lamp biomicroscopy. Some minor pathologic changes were also found elsewhere in the cornea, including epithelial remodelling anterior to the hydrogel implant and a few vacuolated endothelial cells posterior to the edges of the implant. Histologically, no inflammatory reaction was seen in either cornea. This primate demonstrates the long-term biocompatibility of hydrogel intracorneal lenses.