SMILE causes less inflammation and apoptosis

Small incision lenticule extraction (SMILE) caused less keratocyte apoptosis, proliferation and inflammation compared with femtosecond laser LASIK, according to data from a recent animal model study.

Researchers at Fudan University, Shanghai, and Bronx Lebanon Hospital Center, Bronx, New York, USA, compared corneal wound healing and inflammation in 36 eyes of 35 rabbits undergoing SMILE to another 36 eyes of 36 rabbits undergoing femtosecond laser LASIK. All eyes were treated to a refractive correction of –6.00 DS/–1.00 DC. These eyes were then compared to 12 eyes that underwent no surgery as controls.

Corneal tissues were evaluated postoperatively at hour 4 and 24 with terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay to detect apoptosis. At postoperative day 3, week 1 and month 1, they underwent immunocytochemistry for Ki67 to detect keratocyte proliferation, at postoperative day 1, day 3 and week 1, with immunocytochemistry for CD11b to detect inflammation.

Researchers found no adverse events after either procedure and postoperative corneal healing was uneventful in all cases. In eyes that underwent the SMILE procedure, there were significantly less TUNEL-positive corneal stromal cells at 4 hours and 24 hours postoperatively compared with the LASIK procedure (P ≤ 0.01). In addition, there were significantly less Ki67-positive cells in the SMILE group compared with the femtosecond laser LASIK group at day 3 and week 1 postoperatively (P

"In our study, CD11b-positive monocyte mediated inflammation was significantly less severe in postoperative week 1 in the SMILE group compared with the femtosecond LASIK group. We hypothesize that this could be due to the following reasons: a small incision for the lenticule extraction will produce fewer chemokines to attract inflammatory cells in the injury; the intrastromal dissection by a femtosecond laser contributes to reduced tissue injury compared with the stroma ablation by an excimer laser; there was less necrotic debris in the interface after refractive lenticule extraction (ReLEx)," concluded lead author Dr Zixian Dong, PhD, of the Institute of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, and fellow researchers.

To access the abstract and full text of the study, visit the British Journal of Ophthalmology.