[Results of a 2-year animal experiment with reticulated polyethylene oxide intrastromal rings]

Gel Injection Adjustable Keratoplasty (GIAK) is a technique previously described by G. Simon for the correction of myopia. Following pachometry, a 0.8 mm wide, 80% deep linear incision is performed 2.5 mm from the apex. Using a guide, a 1 mm wide, 5 mm diameter annular spatula is introduced to dissect an interlamellar canal and the crosslinked polyethylene oxide hydrogel is injected with a modified 23 gauge needle. The biocompatibility to 13 PEO batches was studied on 21 albino rabbits (Follow up 15 to 135 days). In nineteen, the cornea remained perfectly transparent. Two animals presented an infection at POD 1. Histopathology showed no endothelial deterioration, no anomaly of the thickness or of the cellular morphology around the injected zone. However some mononuclear cells were noticed surrounding the hydrogel in some rabbits together with thinning of the corneal epithelium anterior to the injected zone. A pilot refractive study was conducted on 5 cats using 2 PEO gels. One cat developed an infection following surgery. A second developed an inflammatory response with corneal neovascularization at POD 8. Thus, these animals were not included in the follow-up study which ranged from 6 to 28 months. Immediately after surgery, the refractive effect, measured with the Canon SK-1 digital autokeratometer, was 5.22 +/- 0.46 D (SD) of flattening. The long term effect (26 months) of the GIAK procedure appears to be stable and safe when using sterile PEO gels made of highly purified materials.