Lipid deposits posterior to impermeable intracorneal lenses in rhesus monkeys: clinical, histochemical, and ultrastructural studies.

Synthetic materials are being evaluated for their potential long-term use in corneal refractive surgery. Clinical and histopathologic studies were performed with polymethylmethacrylate (PMMA) and polysulfone intracorneal lenses in rhesus monkey eyes that were followed for up to 3 years. The 5 mm diameter lenses were placed in the deep posterior corneal stroma of four eyes. Fine, polychromatic crystalline deposits formed a layer posterior to the implants. Enucleated eyes had the corneas either frozen for histochemistry or fixed for electron microscopy. Special stains included oil red 0 and filipin on fresh frozen tissue. The cornea, with a PMMA intracorneal lens showed myriad crystalline aggregates in the deep corneal stroma behind the implant. These crystalline deposits stained positively with oil red 0 and with filipin indicating the presence of neutral fat as well as unesterified cholesterol. The polysulfone implant showed no evidence of crystalline deposits histologically but was surrounded by homogeneous aggregates that could represent nonspecific reaction to the lens material or protein deposits. Electron microscopy of all four corneas revealed dissolved lipid aggregates and laminated electron dense material that were most abundant posterior to the implant where the keratocytes appeared disintegrated. The PMMA lens appeared to induce lipid keratopathy.