Two-year observation of morphologic and histopathologic changes in the monkey cornea following small incision allogenic lenticule implantation

To observe the morphologic and histopathologic changes of femtosecond laser assisted small incision allogenic intrastromal lenticule implantation (AILI) in monkey corneas.

6 healthy adult monkeys were included. One eye of two monkeys and both eyes of one monkey received femtosecond lenticule extraction with a -4.0 diopter (D) correction. Each extracted refractive donor lenticule was immediately allogeneically transplanted into a corneal stromal pocket created by a femtosecond laser in another monkey's eye. A postoperative two-year follow-up was performed with slit lamp microscopy, corneal topography, anterior segment optical coherence tomography and in vivo confocal microscopy. All eyes were enucleated for Hematoxylin-Eosin staining and transmission electron microscopy (TEM) observation.

No complications were observed in the follow-up period. At postoperative 2 years, the corneas remained clear and the lenticules were integrated with the surrounding tissue under slit lamp microscopy. Nerve fiber regeneration was detected in the lenticule layer as observed through confocal microscopy. Corneal power was increased by 1.83 ± 1.36 D after 2 years, which was less than at 6 months (3.27 ± 1.2 D). Disordered fibers and decreased keratocytes in the implanted lenticules could be detected under light microscopy and TEM, with a clear boundary between the lenticules and the surrounding tissue.

Small incision AILI is feasible and safe for reshaping the cornea. Corneal healing remained stable while refraction showed a moderate regression within postoperative 2 years.