Immunohistochemical study of corneal inflammation after femtosecond laser clear corneal incisions or manual surgery

Purpose To use immunohistochemical staining to evaluate corneal inflammation and apoptosis induced after femtosecond laser incisions or manual incisions. Setting Ophthalmology Clinic, University G. d'Annunzio, Chieti, Italy. Design Experimental study. Methods Ninety human cadaver corneas were cut manually or with the femtosecond laser at different energies and analyzed by immunohistochemistry after 5 minutes or 4 hours. The corneas were divided into 5 groups: untreated (Group 1), cut manually (Group 2), and treated with the femtosecond laser with increasing energies (Groups 3 to 5; 3.0 μJ, 6.0 μJ, and 15.0 μJ, respectively). Results At 5 minutes, increased expression of interleukin (IL)-18 was observed in the femtosecond laser groups compared with the manual group (P < .01). Interferon gamma (IFNγ) positivity was significantly higher in Groups 4 and 5 than in Group 2 and between Groups 3 and 4 (P < .05). The terminal uridine deoxynucleotidyl nick end-labeling (TUNEL) positivity increased with higher energy (Group 2 versus Group 4 and Group 2 versus Group 5; P < .05). After 4 hours, IFNγ positivity was higher in Group 5 than in Group 2 (P = .0021) and between Group 5 and Groups 3 and 4 (P < .05). No sign of IL-18 positivity was found after 4 hours in any sample. Group 5 showed significant higher TUNEL positivity than all other groups (P < .0001). Conclusion The femtosecond laser technique at high energies induced a higher corneal inflammatory response and a higher corneal cell apoptosis than the manual technique. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned.