Comparison between Pentacam HR and Orbscan II after Hyperopic Photorefractive Keratectomy.

Farshad Askarizadeh,Mohammadaghazadeh Amiri,Hadi Ghadimi,Bahram Khosravi,Mahmoud Jabbarvand,Foroozan Narooie-Noori,Mohamadreza Sedaghat

doi:10.4103/jovr.jovr_47_17

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.

Highlights

Photorefractive keratectomy (PRK) remodels the anterior corneal surface to correct refractive errors, allowing cornea to focus the light rays on the retina by adjusting its refractive power
A strong correlation was observed between the two imaging devices for A‐best‐fit sphere size (BFS), posterior best fit sphere (P‐BFS), A‐central elevation (CE), A‐tangential power in 3 mm (TG3), and central corneal thickness (CCT) but the correlation was weak for posterior central elevation (P‐CE), anterior chamber depth (ACD), and A‐TG5
We studied hyperopic patients who underwent PRK

Summary

Introduction

Photorefractive keratectomy (PRK) remodels the anterior corneal surface to correct refractive errors, allowing cornea to focus the light rays on the retina by adjusting its refractive power. How to cite this article: Jabbarvand M, Askarizadeh F, Sedaghat MR, Ghadimi H, Khosravi B, Amiri MA, et al Comparison between Pentacam HR and Orbscan II after hyperopic photorefractive keratectomy. Orbscan II and Pentacam HR are widely used for this purpose.[1,2] Each uses a different method for imaging the cornea; slit‐scanning is used by Orbscan II and the Scheimpflug principle is used by Pentacam HR.[2] Numerous studies have been published investigating agreement between the two devices with respect to different anterior and posterior corneal parameters.[2,3,4,5] a majority of these studies have been performed on myopic patients rather than the less commonly encountered hyperopic patients.[2,3,4,5,6,7] most of the previous studies have included patients who had undergone laser in situ keratomileusis (LASIK),[8,9] whereas studies on patients who have undergone hyperopic photorefractive keratotomy (H‐PRK) are scarce. The accuracy of tonometry is affected by the central corneal thickness (CCT), which is another parameter measured using ultrasonic and optical devices.[11,12]

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