Higher order wavefront aberrations and topography in early and suspected keratoconus

PURPOSE: To determine whether higher order wave-front aberrations or a combination of topography and wavefront variables distinguishes between early and suspected keratoconus. METHODS: This prospective comparative study evaluated 70 eyes using videokeratography (Tomey TIVS-1) and aberrometry (Alcon LADARWave). Videokeratography and clinical evaluation were used to divide the eyes into three groups: 50 normal eyes, 10 eyes with early keratoconus, and 10 eyes with suspected keratoconus. Data were analyzed to determine whether higher order aberrations could separate eyes with early and suspected keratoconus from normal eyes. The product of the Inferior-Superior (I-S) topographic value in combination with the wavefront vertical coma also was evaluated to determine whether this could distinguish normal eyes,from eyes with early and suspected keratoconus. RESULTS: Differences in vertical coma, root-mean-square coma, and secondary astigmatism for the three groups were statistically significant. Vertical coma was -0.03 +/- 0.28 for normal eyes, -0.525 +/- 0.253 for eyes with suspected keratoconus, and -1.949 +/- 1.416 for eyes with early keratoconus. Root-mean-square coma was 0.229 +/- 0.149 for normal eyes, 0.639 +/- 0.250 for eyes with suspected keratoconus, and 2.034 +/- 1.532 for eyes with early keratoconus. The product of vertical coma and the topographic I-S value separated the three groups better than aberrometry alone (P<.0001). CONCLUSIONS: Although both vertical coma and the I-S topographic value were useful for distinguishing among the three study groups, a combination of wavefront aberrometry and videokeratography appears to,be the most sensitive way for distinguishing among normal eyes, eyes with suspected keratoconus, and eyes with early keratoconus.