Refractive keratoplasty procedures for large dioptric corrections utilize a lenticular addition to the cornea which is typically cut from a donor cornea, but can also be fabricated from hydrogel plastics (1). The success of an intrastromal hydrogel implant depends on the nonreactiveness of both the hydrogel to the stroma tissue and the tissue environment to the hydrogel. Permalens hydrogel (Cooper Labs, Inc.) was fabricated into 6 mm diameter, 0.24 mm thick, and +15.00 diopter lenticules and surgically implanted into intracorneal pockets of rabbit corneas for eleven months. Light and electron microscopy revealed scattered zones of abnormal fibroblast activity at the posterior interface of the hydrogel and stroma. The anterior pocket lining was covered with a single cell layer of keratocytes, but there were no irregular areas that might be light scattering. The remaining ultrastructure appeared normal. Preliminary work with primates did not reveal this type of abnormal fibroblast activity. The data indicates that hydrogels for intrastromal implantation in refractive keratoplasty have a promising future.