Corneal surface topography and associated visual performance with INTACS for myopia: Phase III clinical trial results

Abstract

Objective To characterize corneal topography with INTACS (KeraVision, Inc., Fremont, CA) an ophthalmic device designed to correct myopia, and relate findings to visual performance. Design Prospective nonrandomized self-controlled comparative intervention study. Participants/intervention Patients were participants in the INTACS FDA phase III clinical trials. Main outcome measures Preoperative and postoperative month 6 videokeratographic corneal topography (EyeSys, Houston, TX) was analyzed for 165 eyes from eight clinical sites. Topographic flattening, asphericity, and surface characteristics were statistically evaluated for relationship to visual acuity, refractive data, contrast sensitivity, and subjective visual symptoms. Results Corneal radius of curvature flattening was aspheric in nature and increased incrementally and significantly for progressively thicker INTACS ( P < 0.05). Comparative stratification analyses suggest potential interactions between existing preoperative asphericity and myopia, postoperative asphericity, and visual performance outcomes. Qualitative symmetric and asymmetric toric topography patterns were related to the postoperative self-reported visual symptoms of “double images” ( P ≤ 0.05) and “halos” ( P ≤ 0.10), respectively. Conclusions The anterior corneal surface is aspherically flattened (prolately) with INTACS, whereas postoperative corneal asphericity is significantly more prolate than preoperative. Specific qualitative postoperative topography patterns were associated with subjective clinical visual performance.