J Korean Ophthalmol Soc.  2013 Sep;54(9):1345-1352.

Comparison of the Refractive Outcomes According to the Differences of Biometry and Keratometry Reading

• Lee KH
• Kim NR
• Seo KY

Abstract

PURPOSE
The purpose of this study was to investigate the error tendency between preoperative expected refraction and postoperative manifest refraction based on axial length, anterior chamber depth, and keratometric data obtained by an automated keratometer and Pentacam(R) in cataract surgery cases and to report how their differences affect determination of intraocular lens (IOL) power.
METHODS
The authors retrospectively reviewed the medical records of 110 eyes of 84 patients who underwent cataract surgery. Axial length and anterior chamber depth were measured by A scan ultrasound biometry, while keratometric values were obtained by an automated keratometer and Pentacam(R). IOL power was calculated using the SRK/T formula. Patients were divided into 3 groups based on the axial length, anterior chamber depth, and the difference of keratometric values between the 2 devices. Refractive error was analyzed 2 months after surgery.
RESULTS
There were no statistically significant differences between axial length and anterior chamber depth among the groups; however, the K reading differences were statistically significant. Although the mean absolute error (MAE) of each group showed no statistical significance among the groups, the MAE was more pronounced in the group in which the keratometeric value measured by Pentacam(R) differed more than 1.00 diopter from the automated keratometer measurements.
CONCLUSIONS
There was no statistically significant difference between axial length and anterior chamber depth among the groups. A difference of 1.00 diopter or more between the keratometric values obtained by an automated keratometer and Pentacam(R) significantly affects the postoperative refractive error; therefore, these factors should be considered when determining IOL power.

Keyword

Biometry; Cataract surgery; Keratometry reading; Refractive outcomes; Scheimpflug photography

MeSH Terms

Anterior Chamber
Biometry
Cataract
Eye
Humans
Lenses, Intraocular
Medical Records
Refractive Errors
Retrospective Studies

Figure

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  Figure 1. Relationship between mean absolute error (MAE) and difference of keratometeric value between Pentacam® and autokeratometer. Note that the majority of large amount of MAE occurs among the group of which keratometer measured by Pentacam differed more than 1.00 diopter from autokeratometer.

• 

  Figure 2. Relationship between mean numeric error (MNE) and difference of keratometeric values between Pentacam® and autokeratometer (Pearson Correlation = -0.272, p < 0.01). Difference of keratometric value between Pentacam® and au-tokeratometer = Pentacam® mean corneal front power kerato-metric value - Autokeratometer mean keratometric value.

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  Figure 3. Comparison of mean absolute error (MAE) of IOL calculation measured by autokeratometer and Pentacam®. IOL power prediction is more accurate measured in groups 1 and 2, than in group 3 of which keratometer values measured by Pentacam® differed more than 1.00 diopter from autokera-tometer (Group 1. vs. Group 2. p = 1.00, Group 2. vs. Group 3. p = 0.00, Group 1. vs. Group 3. p = 0.00, ANOVA test).

• 

  Figure 4. Comparison of the percentage of patients achieving a mean absolute error (MAE) within 1.0 D of predicted value measured by autokeratometer and Pentacam®. Note that the majority of patients above the 1.0 D MAE values occurred among the group with Pentacam® photography equivalent K reading applied MAE of group 3. This was significantly high-er than any other groups as assessed by Kruskal-wallis test (p < 0.01). Group 1 = Absolute value of difference of keratometer between Pentacam® and autokeratometer, <0.50; Group 2 = Absolute value of difference of keratometer between Pentacam® and autokeratometer, 0.50 ≤ and <1.00; Group 3 = Absolute value of difference of keratometer between Pentacam® and au-tokeratometer, ≥ 1.00.

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