Scanning-slit and Specular Microscopic Pachymetry in Comparison With Ultrasonic Determination of Corneal Thickness

Abstract

The results indicate that the devices tested cannot be simply used interchangeably. For long-term patient follow-up, one specific instrument is recommended. Recently developed pachymetry machines are especially helpful when additional corneal data such as thickness profile, elevation maps, anterior chamber depth, and endothelial morphology are required.

Repeatability of central corneal thickness measurements measured with the Topcon SP2000P specular microscope

“…One other study [16] assessed only the withinobserver repeatability and found that the variability of repeated CCT measures was greatest with the SP2000P specular microscope compared with ultrasound pachymetry and ultrasound biomicroscopy. Tam et al [16] also reported higher values for average CCT measured with the SP2000P specular microscope compared with the other two techniques, in contrast with the results from other studies [2,9,13]. Repeatability in the Tam [16] study was computed by calculating the standard deviation of triplicate CCT measurements made for each subject.…”

Comparison of Pentacam Scheimpflug Camera with Ultrasound Pachymetry and Noncontact Specular Microscopy in Measuring Central Corneal Thickness

“…9,[24][25][26] The current result estimated it to be about 552 μm. Most of the previous studies demonstrated that the CCT measured with the NCSM was thinner than that measured with the US, whereas the current study has not found a significant difference between the two.…”

Orbscan computerized topography: Attributes, applications, and limitations

“…24,[39][40][41] However, from the initial publications, it is apparent that in normal corneas, the Orbscan technique consistently produces pachymetry measurements thicker than US by approximately 30 mm. [42][43][44][45] Several explanations for this discrepancy have been proposed, the most plausible being that US can compress the tissue, whereas the Orbscan optical technique also measures the tear film and mucus layer, although this is unlikely to explain the magnitude of the discrepancy. Some reports describe a significant variation in the Orbscan-US relationship across the surface of the cornea.…”