[Analysis of corneal curvature alteration following intrastromal corneal ring implantation: experimental study in rabbits].

PURPOSE To evaluate the effect of intrastromal corneal ring implantation on corneal curvature in rabbits. METHODS Thirty eyes of 15 rabbits were divided into two groups: group 1 with 7 animals and group 2 with 8 animals. The left eye underwent surgery and the right eye was used as control. Ultrasound pachymetry and corneal topography were performed prior to surgery. Anterior segment biomicroscopy and corneal topography were performed after surgery. In group 1, implantation of two ring segments was performed. In group 2, ring segments were implanted separately. Topographical findings, before and after surgery, were compared through quantitative and qualitative alterations and divided into four quadrants. RESULTS Quantitative analysis showed no significant difference between the groups in the preoperative period. Experiment group 1 showed nasal (p=0.02) and temporal (p=0.04) corneal steepening, compared to control group 1. Experiment group 2 showed nasal and temporal corneal steepening and superior and inferior corneal flattening (p=0.02 for all quadrants) compared to the control group 2. Qualitative analysis showed uniform astigmatism in both control groups. In experiment group 1, against-the-rule regular symmetrical astigmatism was observed after surgery. In experiment group 2, against-the-rule regular asymmetrical astigmatism was found after implantation of the first ring segment, and against the rule regular symmetrical astigmatism was observed after implantation of the second segment. CONCLUSION In this study, significant corneal flattening occurred in quadrants where ring segments extremities were located and corneal steepening was observed in quadrants where its body was located. Implantation of one ring segment induces asymmetrical astigmatism.