Repeatability of automatic measurements by a new Scheimpflug camera combined with Placido topography.

PURPOSE: To assess the repeatability of anterior segment measurements performed by a Scheimpflug camera combined with Placido corneal topography (Sirius) in unoperated, post-refractive surgery, and keratoconus eyes.

SETTING

Private clinical ophthalmology practice.

DESIGN

Evaluation of diagnostic test or technology.

METHODS

Three consecutive scans were acquired for each eye. The following parameters were evaluated: simulated keratometry, posterior corneal power, mean pupil power (ie, corneal power assessed by ray tracing through the anterior and posterior corneal surfaces), corneal asphericity, thinnest and apex corneal thickness, aqueous depth, anterior chamber volume, and corneal spherical aberration. Repeatability was assessed using test-retest variability, the coefficient of variation, and the intraclass correlation coefficient (ICC).

RESULTS

Sixty-four unoperated eyes, 17 eyes that had myopic excimer laser surgery, and 13 eyes with keratoconus were analyzed. High repeatability was achieved for most parameters in the 3 groups, with an ICC higher than 0.99 for all measurements except posterior corneal power and mean pupil power in keratoconus (ICC, 0.868 and 0.976, respectively), anterior and posterior asphericity in normal eyes (ICC, 0.904 and 0.977, respectively), and spherical aberration in normal eyes (ICC, 0.806), post-refractive surgery eyes (ICC, 0.980), and keratoconus eyes (ICC, 0.981).

CONCLUSION

The anterior segment measurements provided by the new Scheimpflug camera-Placido corneal topography system were highly repeatable and can be relied on in clinical routine and for research purposes.

FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.