[The histopathological observation of rabbit corneas after small incision lenticule extraction].

OBJECTIVE: To evaluate the morphological changes during corneal wound healing after small incision lenticule extraction (SMILE).

METHODS: Twenty-one New Zealand white rabbits were randomly divided into 2 groups (group A of 12 rabbits and group B of 9 rabbits) using the toss of a coin. All the right eyes were treated. Group A underwent SMILE, and group B underwent femtosecond laser-assisted in situ keratomileusis (LASIK), with the same refractive corrections of-6.00 DS/-1.00 DC. The surface regularity on the refractive corneal lenticules and flaps was evaluated by scanning electron microscopy. Light microscopy and transmission electron microscopy were applied to observe changes in the cornea on postoperative week 1, months 1 and 3. The contralateral eye of three rabbits served as control.

RESULTS: All the operations were successful, and the postoperative corneal healing was uneventful in both groups. The recovery of corneas was faster in the SMILE group by slit-lamp examination. Light microscopy confirmed the mild edema of corneal stroma with a clear intrastromal crevice in the SMILE group and the adhesion of the flap and stromal bed in the LASIK group on postoperative week 1. The filling of epithelial cells at the flap margin and the irregular arrangement of collagens were demonstrated in both groups. On postoperative month 1, stromal edema was dissipated, and collagens became more regular in both groups. The intrastromal crevice in the SMILE group disappeared on postoperative month 3. Transmission electron microscopy also revealed the edema of keratocyte mitochondria within 1 month, and the keratocytes recovered to normal on month 3. The surface regularity of the front surface was better than that of the back.

CONCLUSIONS: Smooth intrastromal lenticules can be safely prepared by femtosecond laser. The corneal healing in the SMILE group was better than that in the LASIK group. The intrastromal crevice in the early postoperative period after SMILE should be paid attention to clinically. (Chin J Ophthalmol, 2016, 52: 507-513).