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J Cataract Refract Surg. 2011 Feb;37(2):295-301. doi: 10.1016/j.jcrs.2010.08.050.

Automated keratometry in routine cataract surgery: comparison of Scheimpflug and conventional values.

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Epsom and St Helier University Hospitals NHS Trust, London, United Kingdom.



To compare the mean keratometry (K) readings obtained with a conventional automated keratometer (IOLMaster) and a Scheimpflug keratometer (Pentacam) in eyes having preoperative assessment for routine cataract surgery.


Epsom and St. Helier University Hospitals, London, United Kingdom.


Evaluation of diagnostic technology.


Mean K values were obtained with the conventional and Scheimpflug keratometers. The following Scheimpflug readings were evaluated: anterior K, true net power, and Holladay equivalent K measured at 1.0 to 7.0 mm corneal diameters. Mean readings for each type of keratometry were compared. Bland-Altman plots were used to determine the 95% limits of agreement (LoA) for the conventional and Scheimpflug keratometers.


The mean conventional K was statistically significantly greater than the mean Scheimpflug K for true net power and equivalent K at 1.0 mm, 2.0 mm, 3.0 mm, and 4.0 mm corneal diameters. The mean conventional K was significantly less than the equivalent K at 5.0 mm, 6.0 mm, and 7.0 mm. The smallest mean difference was for equivalent K at 4.5 mm (0.02 diopters [D]). The smallest 95% LoA were -0.68 to 1.16 D (equivalent K at 5.0 mm) and -0.91 to 0.95 D (equivalent K at 4.5 mm).


Overall, the equivalent K at 4.5 mm had the closest match with the conventional K values. The degree of interdevice variability with the conventional keratometer was lowest for the equivalent K at 4.5 mm and 5.0 mm, although this variability would be sufficient to influence intraocular lens power selection.

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