Journal of Refractive Surgery

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Original Article 

Agreement Between Pentacam and Videokeratography in Corneal Power Assessment

Piero Barboni, MD; Giacomo Savini, MD; Michele Carbonelli, MD; Kenneth J. Hoffer, MD, FACS

Abstract

PURPOSE

To investigate agreement between a rotating Scheimpflug camera (Pentacam, Oculus Optikgeräte GmbH) and two corneal topographers (TMS-2 Topography System, Tomey; and Keratron Scout, Optikon 2000 SpA) in measuring the corneal power of normal eyes.

METHODS

The mean corneal powers calculated by simulated keratometry (SimK) with each topographer were compared to those provided by the Pentacam in 71 patients. Specifically, the corneal power values of the Pentacam included in this analysis were the SimK (calculated using the measured anterior corneal radius and standard keratometric index of 1.3375) and the True net power (calculated using the anterior and posterior corneal curvatures and Gaussian optics formula for thick lenses, where the actual refractive index of the air, cornea, and aqueous humor are entered). Bland-Altman plots were used to investigate agreement and analysis of variance (ANOVA) was performed to detect statistical differences.

RESULTS

Although ANOVA did not disclose a statistically significant difference among the mean SimK values (TMS-2: 43.20±1.51 diopters [D], Keratron Scout: 43.29±1.48 D, Pentacam: 43.25±1.53 D), the 95% limits of agreement between the TMS-2 and Pentacam and between the Keratron Scout and Pentacam were wide (–1.05 to +0.94 D and –0.95 to +1.02 D, respectively). Agreement was even poorer when considering the mean True net power (42.00±1.54 D), which was significantly lower than the mean Pentacam SimK (P<.001).

CONCLUSIONS

Although corneal topography and the Pentacam provide similar SimK values, their data should not be used interchangeably as only moderate agreement exists between them. Corneal power values calculated by the True net power are significantly lower than any SimK and cannot be entered into intraocular lens power formulas. [J Refract Surg. 2009;25:534-538.]

doi:10.3928/1081597X-20090512-07

AUTHORS

From Studio Oculistico d’Azeglio, Bologna, Italy (Savini, Barboni, Carbonelli); and Jules Stein Eye Institute, University of California, Los Angeles, Calif (Hoffer).

The authors have no proprietary interest in the materials presented herein.

Correspondence: Giacomo Savini, MD, Studio Oculistico d’Azeglio, Via d’Azeglio 5, 40123 Bologna, Italy. Tel: 39 051 6493203; E-mail: giacomo.savini@alice.it

Received: March 15, 2008; Accepted: June 20, 2008

Posted online: July 31, 2008

Abstract

PURPOSE

To investigate agreement between a rotating Scheimpflug camera (Pentacam, Oculus Optikgeräte GmbH) and two corneal topographers (TMS-2 Topography System, Tomey; and Keratron Scout, Optikon 2000 SpA) in measuring the corneal power of normal eyes.

METHODS

The mean corneal powers calculated by simulated keratometry (SimK) with each topographer were compared to those provided by the Pentacam in 71 patients. Specifically, the corneal power values of the Pentacam included in this analysis were the SimK (calculated using the measured anterior corneal radius and standard keratometric index of 1.3375) and the True net power (calculated using the anterior and posterior corneal curvatures and Gaussian optics formula for thick lenses, where the actual refractive index of the air, cornea, and aqueous humor are entered). Bland-Altman plots were used to investigate agreement and analysis of variance (ANOVA) was performed to detect statistical differences.

RESULTS

Although ANOVA did not disclose a statistically significant difference among the mean SimK values (TMS-2: 43.20±1.51 diopters [D], Keratron Scout: 43.29±1.48 D, Pentacam: 43.25±1.53 D), the 95% limits of agreement between the TMS-2 and Pentacam and between the Keratron Scout and Pentacam were wide (–1.05 to +0.94 D and –0.95 to +1.02 D, respectively). Agreement was even poorer when considering the mean True net power (42.00±1.54 D), which was significantly lower than the mean Pentacam SimK (P<.001).

CONCLUSIONS

Although corneal topography and the Pentacam provide similar SimK values, their data should not be used interchangeably as only moderate agreement exists between them. Corneal power values calculated by the True net power are significantly lower than any SimK and cannot be entered into intraocular lens power formulas. [J Refract Surg. 2009;25:534-538.]

doi:10.3928/1081597X-20090512-07

AUTHORS

From Studio Oculistico d’Azeglio, Bologna, Italy (Savini, Barboni, Carbonelli); and Jules Stein Eye Institute, University of California, Los Angeles, Calif (Hoffer).

The authors have no proprietary interest in the materials presented herein.

Correspondence: Giacomo Savini, MD, Studio Oculistico d’Azeglio, Via d’Azeglio 5, 40123 Bologna, Italy. Tel: 39 051 6493203; E-mail: giacomo.savini@alice.it

Received: March 15, 2008; Accepted: June 20, 2008

Posted online: July 31, 2008

10.3928/1081597X-20090512-07

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