3-D Shape of Biomimetic Corneal Substitutes in the Living Human Eye

Abstract

Purpose: : To characterize the 3-D shape of corneas implanted with the first biomimetic corneal substitutes (BCS) and to compare this shape to that of normal corneas, based on the integrated analysis of Orbscan corneal topography average models (atlases).

Methods: : This study was conducted on 10 eyes of the first 10 subjects implanted with biomimetic corneal substitutes. All surgeries were performed by Dr. Per Fagerholm at the Linköping University Hospital, Sweden, between October and November 2007. Serial Orbscan II (Bausch and Lomb, Rochester, New York, USA) corneal topographies were performed on all eyes and several topography parameters were analyzed. Four-year follow-up was available for most subjects. Ten normal controls (spherical equivalent within ± 2.00 D and cylinder within ± 1.00 D from emmetropia) were matched for age and gender to each tested subject. 3-D atlases were constructed for the 10 BCS corneas and all 100 controls. Each atlas illustrated mean anterior elevation, mean posterior elevation and mean pachymetry. Difference maps and statistics maps were generated to compare the "BCS corneas" and "All controls" atlases.

Results: : Preliminary results show a smooth integration of the BCS surgical wound within the anterior surface profile, without significant steps or gaps. The Thinnest point was thinner (mean ± SEM: BCS: 266.22±29.88 µm; Controls: 570.86±4.03 µm; p < 0.001) and more inferiorly located (BCS: -1.04±0.24 mm from the center of the topography; Controls: -0.13±0.05 mm; p < 0.001) in BCS corneas, but did not seem to be displaced laterally (BCS: -0.21±0.29 mm, Controls: -0.42±0.04 mm; p = 0.1900). In the central 3.0 mm radius area, Surface irregularity (BCS: 8.81±1.15 D, Controls: 1.26±0.04 D; p < 0.001), Mean power (BCS: 49.23±1.92 D; Controls: 43.60±0.16 D; p <0.001) and Astigmatic power (BCS: 5.46±1.83 D; Controls: 0.74±0.05 D; p < 0.001) were increased in BCS corneas. Similar findings were observed in the annular 3.0-5.0 mm zone (p < 0.001).

Conclusions: : This comparative study will allow detailed characterization of the differences in shape between BCS corneas and corneas of normal emmetropic subjects matched for age and gender, in order to help optimize the shape of future BCS corneas.

Keywords: topography • transplantation • cornea: clinical science