Comparison between pentacam HR and Orbscan II after hyperopic photorefractive keratectomy

Abstract

Purpose:The aim of this study was to determine the agreement between Pentacam HR (Scheimpflug imaging, Oculus) and Orbscan II (scanning slit topography, Bausch and Lomb) in measuring corneal parameters after photorefractive keratectomy (PRK) for hyperopia.Methods:In this prospective cross-sectional study, 38 hyperopic eyes undergoing PRK were examined before refractive surgery and 8 to 10 months postoperatively using Pentacam HR and Orbscan II. Ultrasound (US) pachymetry was also used to measure central corneal thickness (CCT). The radius of anterior (A-) and posterior (P-) best-fit sphere size (BFS), central elevation (CE), and anterior maximum tangential power in 3 mm (TG3) and 3-5 mm (TG5) zones, anterior chamber depth (ACD), and central corneal thickness (CCT) were collected and used in the analyses. To study the agreement between the measurements made by the two devices, the method described by Bland and Altman was used and the 95% limits of agreement were calculated.Results:The 95% limits of agreement show reasonable agreement between the measurements by Pentacam HR and Orbscan II for A-BFS, P-BFS, A-TG3, and CCT, but not for A-CE, P-CE, A-TG5, or ACD. CCT values obtained by both Pentacam HR and Orbscan II correlated well with the values determined by US pachymetry.Conclusion:Pentacam HR and Orbscan II after PRK for hyperopia show reasonable agreement for determining A-BFS, P-BFS, A-TG3, and CCT, but not for A-CE, P-CE, A-TG5, or ACD. CCT measurements with Pentacam HR have reasonable agreement with US pachymetry.

Author's reply

“…In addition, the 95% limits of agreement between ultrasound pachymetry and Pentacam HR was better than that between ultrasound pachymetry and Orbscan II. [ 1 ] These results contrast with the findings of Rosa and associates. Dissimilarity between the results of the study conducted by Rosa et al[ 6 ] and those of the present study[ 1 ] may be related to hyperopic PRK.…”

“…[ 1 ] These results contrast with the findings of Rosa and associates. Dissimilarity between the results of the study conducted by Rosa et al[ 6 ] and those of the present study[ 1 ] may be related to hyperopic PRK. Notably, PRK is the most important factor to be considered in our study.…”

“…We refer Bernardo and Rosa to the Methods and Results of our study, where we compared various corneal topographic and tomographic parameters measured by Orbscan II and Pentacam HR to determine the agreement between these two devices in analysis of hyperopic patients who have had hyperopic PRK. [ 1 ] Notably, CCT was just one of the parameters measured in our study. We mentioned in the Methods section of our article that all included patients had normal virgin corneas before hyperopic PRK.…”

“…We express our sincere thanks to Dr. Bernardo and Dr. Rosa for their interest in our study and their letter on our work. [ 1 ] Bernardo and Rosa noted the significance of central corneal thickness (CCT) in virgin eyes and after photorefractive keratectomy (PRK), as evaluated by Pentacam HR (Scheimpflug imaging) and Orbscan II (scanning slit topography). They concluded that the difference between Pentacam and Orbscan in measuring corneal thickness is related to differences in the devices, rather than corneal changes induced by hyperopic PRK.…”

Corneal thickness measurement after hyperopic photorefractive keratectomy

“…We read with great interest the article by Jabbarvand et al comparing Pentacam HR and Orbscan II measurements after hyperopic photorefractive keratectomy (PRK). [ 1 ]…”