Effects of Intrastromal Air Injection Compared to Hydro-injection on Keratocyte Apoptosis

ABSTRACT

PURPOSE: To evaluate the effects of intrastromal air injection and intrastromal balanced salt solution (BSS) injection on corneal keratocyte apoptosis. METHODS: Twelve right eyes of New Zealand White rabbits were divided into an air-injected group (n=6) and a hydro-injected group (n=6). Contralateral eyes served as a control. Air or Balanced salt solution (BSS(R), Alcon, USA) was injected into the deep corneal stroma at the paracentral area to propagate into nearly the entire cornea. To reduce the intraocular pressure, anterior chamber paracentesis was performed. The animals were sacrificed 4 hours (n=6) and 24 hours (n=6) after surgery. Central cornea buttons were retrieved to stain with Hematoxylin & Eosin and TUNEL (Apoptag(R), Chemicon). The mean number of apoptotic keratocytes was counted in 24.67+/-4.04 consecutive high power field (HPF). RESULTS: The mean number of TUNEL-positive cells at 4 hours was 12.85+/-7.25/HPF and 0.25+/-0.44/HPF in air-injected and hydro-injected eyes, respectively. It was reduced to 6.25+/-4.02/HPF and 0.15+/-0.37/HPF in air-injected and hydro-injected eyes after 24 hours. The air-injected group showed significantly more TUNEL-positive cells compared with the hydro-injected or control group until 24 hours (p=0.001, p=0.001, Mann-Whitney U test). CONCLUSIONS: Intrastromal air injection induces significant apoptosis of keratocytes suggesting some damages in the peripheral cornea when used in deep lamellar keratoplasty.