Air and SF6 Corneal Endothelial Toxicity

Abstract

Purpose: : In vivo assessment of corneal endothelial toxicity of AIR and SF6 in the feline model.

Methods: : In a prospective randomized study, in which the observers were blinded to choice of treatment, 12 healthy adult animals received an anterior chamber (AC) injection of 0.7 ml of AIR in one eye and 0.7 ml of 20% SF6 in the contralateral eye. Pre and postoperative daily examination included slit lamp assessment, pachymetry and tonometry. Specular microscopy was performed before and after injection at day 7 and 10. The animals were euthanized on day 10 and all eyes were fixed in formaldehyde for histopathology (hematoxylin and eosin stain).

Results: : Preliminary results showed that SF6 remained longer than AIR in the AC (p<0.001). No difference in IOP was observed between the AIR and SF6 eyes (p=0.740), both groups showing a moderate IOP raise early after surgery, followed by a rapid return to normal values (mean ± SD on day 10: AIR:18.1±3.9 mmHg and SF6: 15.4±5.5 mmHg). In both groups, a postoperative inflammatory response was observed, which was greater in eyes injected with SF6 (AC cells: p=0.004; flare: p=0.027). A significant decrease in endothelial cell counts was observed at days 7 & 10 (mean cell count ± SD (cells/mm² )): AIR: 2441±163 and SF6: 2303±201) compared with preoperative values (AIR: 2401±123 and SF6=2469±210) (p=0.022).

Conclusions: : Preliminary results seem to indicate that in the feline model, SF6 is more toxic than AIR in terms of endothelial cell counts and anterior chamber inflammation. Determination of AIR vs SF6 endothelial toxicity will be important for surgeries such as Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) in which air is routinely injected in the anterior chamber and for increasing periods of time.

Keywords: cornea: endothelium • ocular irritancy/toxicity testing • inflammation