Effect of Different Intracorneal Ring Composites Shift on Clinical and Optical Outcome

Abstract

Purpose: : To evaluate the outcome and potential of implanting methyl methacrylate/2 ethyl hexyl acrylate (MMA/EHA) acrylic copolymer as a device to correct, stabilize, and improve the effect of Poly(methyl methacrylate) (PMMA) intracorneal rings.

Methods: : MMA/EHA segments were implanted in the right corneas of ten Lohmann Classic hens. In the left fellow eyes PMMA rings (Ferrara) were implanted. The dimensions of the MMA/EHA and PMMA segments were the same (90º arc, 150 µm thickness). Corneal radius of curvature was measured using a custom-built videokeratometer, refractive state was analyzed with an automated eccentric infrared photorefractor and corneal thickness was assessed with ultrasound pachymetry. The outcomes were evaluated at 15, 30, 60 and 90 days in all eyes. Direct transmittance was measured at 30 and 90 days using a scatterometer developed by our group. All eyes were fixed for histological analysis.

Results: : Significant central and peripheral flattening of the cornea was obtained, the flattening reached the same extent and remains stable over time in both segments, MMA/EHA and PMMA. A significant difference in postoperative refractive state was observed in MMA/EHA and PMMA groups compared with preoperative values. At 15 days corneal thickness recovered its normal value in both groups. MMA/EHA segments showed a higher value of direct transmittance than PMMA.

Conclusions: : The experimental results obtained with this copolymer give reason to consider it suitable for a composite intracorneal implant.

Keywords: refractive surgery: other technologies • cornea: clinical science • keratoconus