Pentacam wave had better repeatability in eyes with a poor tear film as compared to iTrace. Tear optics affected repeatability of Pentacam wave and iTrace. Maximum variation was seen with HOA and minimum with LOA. In eyes with OSI ≥1, the repeatability with Pentacam AXL wave dropped with ICC ranging from 0.77 for HOA, to 0.84 for LOA with lower Sw, TRT, and COV of all aberration measurements as compared to iTrace. The Sw, TRT, and COV of all aberration measurements were significantly lower (better) than those of iTrace. All measurements with Pentacam AXL wave with OSI < 1 had excellent repeatability, intraclass correlation coefficient (ICC) ranging from 0.88 for HOA, to 0.92 for LOA.

OSI showed an inverse association with TBUT (P < 0.001). Repeatability of Pentacam AXL wave and iTrace in healthy and postrefractive eyes (OSI >1 vs OSI <1) was studied using within-subject standard deviation (Sw) test-retest repeatability (TRT), coefficient of variation (COV). They underwent optical quality analyzer (OQAS, Visio metrics S.L, Terrassa, Spain) to assess objective scatter index (OSI), three scans each on Pentacam AXL wave (OCULUS Optikgerate Gmbh, Wetzlar, Germany), iTrace (Tracey™ Technologies, Texas, USA) for flat, steep keratometry, thinnest corneal thickness, root mean square higher-order aberrations (RMS HOA), RMS lower-order aberrations (LOA), spherical aberrations, RMS COMA. One hundred healthy and 100 postrefractive surgery eyes underwent dry eye evaluation including Schirmer's test and tear film break-up time (TBUT). To assess impact of tear optics on repeatability of a Scheimpflug device with a Hartmann Shack aberrometer and a ray tracing aberrometer.

Tracey itrace used