Corneal asphericity in eye bank eyes implanted with the intrastromal corneal ring.

OBJECTIVE To evaluate the effects of the intrastromal corneal ring, a device developed to reduce myopia, on corneal asphericity in a large set of eye bank eyes. METHODS Forty-one deturgesced eye bank eyes were implanted with intrastromal corneal rings of five different thicknesses, ranging from 0.25 mm to 0.45 mm. Corneal asphericity, before and after implantation, was examined using two different metrologies. Corneal asphericity profiles were produced from dioptric power data collected from videokeratography. To statistically assess the corneal asphericity differences between exam times for each intrastromal corneal ring thickness, dependent sample confidence intervals (95%) were calculated for the mean differences between preoperative and postoperative measures for each topographic diameter zone. Laser holographic interferometry was used to inspect corneal asphericity in one eye bank eye case study for four intrastromal corneal ring sizes. Wave unit map and geometric zonal spot ray tracing analyses derived from laser holographic interferometry topography were surveyed. RESULTS Videokeratographic analysis suggested that preoperative corneal shape was prolate, i.e., flattened from central to paracentral cornea. Corneal shape became more prolate with intrastromal corneal ring implantation for all intrastromal corneal ring thicknesses. Laser holographic interferometry demonstrated that prolate asphericity was preserved with the intrastromal corneal ring sizes tested and that optical collection efficiency of the cornea was not diminished. CONCLUSION Using two different measurement techniques, this eye bank eye study demonstrated that intrastromal corneal rings maintain prolate corneal asphericity.