Refractive keratoplasty in monkeys using intracorneal lenses of various refractive indexes

The refractive power of the cornea can be altered with an intracorneal lens when it is inserted within a freehand lamellar-pocket incision. The effectiveness of the implant in altering the refractive power of the cornea depends on the refractive index of the intracorneal lens, since little change in the anterior corneal curvature occurs. Thirteen nonhuman primate eyes received intracorneal lenses made of synthetic polymers with refractive indexes ranging from 1.3686 to 1.633. The lidofilcon-B hydrogel (refractive index, 1.3686) lenses created no significant alteration in the refractive power of the cornea. The polymethylmethacrylate (refractive index, 1.4900D) and polysulfone (refractive index, 1.633) lenses created a predictable and significant alteration of corneal power that increased with each implant with a successively higher refractive index. The polymethylmethacrylate lens created a refractive alteration that was approximately 31% of the lens power in air. The polysulfone lens created a corneal power alteration that was approximately 40% of the lens power in air.