Repeatability and Reproducibility of Posterior Corneal Curvature Measurements by Combined Scanning-Slit and Placido-Disc Topography after LASIK

Intrasession and intersession repeatability of the Pentacam system on posterior corneal assessment in the normal human eye

“…Maldonado et al 15 recently reported good intrasession and intersession repeatability of Orbscan on posterior BFS at the 5.0 mm zone. The within-visit ICC was 0.98, and the width of the between-visit 95% LoA was 250 mm.…”

“…Maldonado et al 15 recently reported that the Orbscan system has good intrasession and intersession repeatability in measuring posterior corneal topography in eyes after myopic LASIK for myopia. Quisling et al 16 used the Orbscan and Pentacam systems in keratoconus eyes and found different posterior best-fit sphere (BFS) and posterior elevation between the 2 systems.…”

Corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus

“…To date, studies of posterior changes in eyes with keratoconus were performed using scanning-slit technology, which has been shown to be inaccurate for some posterior corneal measurements in eyes that have had laser in situ keratomileusis (LASIK). [12][13][14][15][16] A fairly recent advance in corneal topography was the introduction of Scheimpflug photography for corneal topographic characterization; this technique allows the study of both the anterior and posterior corneal surfaces 17 and provides more repeatable and reproducible anterior and posterior measurements of corneal power than scanning-slit technology. Kawamorita et al 18 reported 0.19 of agreement for withinrater consecutive measurements of posterior corneal power measurements of diopter (D) with a Scheimpflug-based system and 0.96 D with a scanning-slit system and for between-rater measurements, of 0.56 D and 1.58 D, respectively.…”

“…Part of this controversy stems from problems with the reliability and reproducibility of some posterior corneal surface measurements in eyes that have had LASIK. [12][13][14][15][16] For example, some posterior radially asymmetric measurements in these eyes, such as eccentricity, as well as measurements in eyes with corneal opacities, are not reliable with devices that use combined scanning-slit and Placido-disk technologies. 12 The Scheimpflug photography-based system used in the present study provides repeatable pachymetric and posterior corneal surface (ie, curvature, elevation, asphericity) measurements.…”

Intrasubject repeatability of corneal morphology measurements obtained with a new Scheimpflug photography–based system

“…These include Scheimpflug photography, a combination of scanning-slit and Placido-disk technologies, very-high-frequency ultrasonography, and optical coherence tomography (OCT). [1][2][3][4] Scheimpflug photography-based systems allow the clinician to obtain a complete analysis of the cornea and the anterior chamber, including the characterization of anterior and posterior corneal surfaces, pachymetric mapping, and measurement of the anterior chamber depth (ACD). All these measurements are obtained quickly and do not require the use of anesthesia or contact with the cornea, as required when using ultrasoundbased systems.…”