Repeatability of automatic measurements performed by a dual Scheimpflug analyzer in unoperated and post-refractive surgery eyes.

PURPOSE

To assess the repeatability of the anterior segment measurements performed with a dual Scheimpflug analyzer (Galilei) in unoperated and post-refractive surgery eyes.

SETTING

Private practice.

DESIGN

Evaluation of diagnostic test.

METHODS

Three consecutive scans were acquired in unoperated eyes and in eyes that had excimer laser surgery for myopia. Unoperated eyes were enrolled from 3 subgroups: younger than 50 years, aged between 50 and 70 years, and older than 70 years. The following parameters were evaluated: simulated keratometry, posterior corneal power, total corneal power, anterior and posterior best-fit sphere radius, mean and thinnest central corneal thickness, anterior chamber depth and volume, horizontal and vertical corneal diameter, iridocorneal angle in the 4 quadrants, and corneal spherical aberration. Repeatability was assessed using analysis of variance (ANOVA), the coefficient of variation (COV), intraclass correlation (ICC), and test-retest variability.

RESULTS

The study evaluated 45 unoperated eyes (n = 45) and 15 post-refractive surgery eyes (n = 15). Each age subgroup in the unoperated group comprised 15 eyes. The ANOVA did not detect significant differences between the 3 measurements for any parameter. The COV was less than 0.5% for corneal power measurements and less than 3.5% for all remaining parameters except spherical aberration (16.68%). The ICC was more than 0.99 for corneal power measurements and more than 0.94 for all remaining parameters.

CONCLUSIONS

The anterior segment measurements provided by the dual Scheimpflug analyzer were highly repeatable. Repeatability did not change with age or after myopic photorefractive keratectomy or laser in situ keratomileusis.