Korean J Ophthalmol.  2014 Dec;28(6):444-450. 10.3341/kjo.2014.28.6.444.

Accuracy of Biometry for Intraocular Lens Implantation Using the New Partial Coherence Interferometer, AL-scan

• Moon SW
• Lim SH
• Lee HY

• KMID: 2345820
• DOI: http://doi.org/10.3341/kjo.2014.28.6.444

Abstract

PURPOSE
To compare the refractive results of cataract surgery measured by applanation ultrasound and the new partial coherence interferometer, AL-scan.
METHODS
Medical records of 76 patients and 104 eyes who underwent cataract surgery from January 2013 to June 2013 were retrospectively reviewed. Biometries were measured using ultrasound and AL-scan and intraocular lens power was calculated using the SRK-T formula. Automatic refraction examination was done 1 month after the operation, and differences between the ultrasound group and AL-scan group were compared and analyzed by mean absolute error.
RESULTS
Mean axial length measured preoperatively by the ultrasound method was 23.53 +/- 1.17 mm while the lengths measured using the AL-scan were 0.03 mm longer than that of the ultrasound group (23.56 +/- 1.15 mm). However, there was not a significant difference in this finding (p = 0.638). Mean absolute error was 0.34 +/- 0.27 diopters in the ultrasound group and 0.36 +/- 0.31 diopters in AL-scan group, which showed no significant difference (p = 0.946) in precision of predicting postoperative refraction.
CONCLUSIONS
Although the difference was not statistically significant, intraocular lens calculations done by the AL-scan were nearly similar in predicting postoperative refraction compared to those of applanation ultrasound, however more precise measurements may be obtained if the axial length is longer than 24.4 mm. Except in the case of opacity in the media, which makes obtaining measurements with the AL-scan difficult, AL-scan could be a useful biometry in cataract surgery.

Keyword

Biometry; Interferometery; Phacoemulsification; Ultrasonography

MeSH Terms

Aged
Anterior Chamber/pathology
Axial Length, Eye/*pathology
Biometry/methods
Female
Humans
Interferometry/*instrumentation
*Lens Implantation, Intraocular
Lenses, Intraocular
Light
Male
Middle Aged
*Phacoemulsification
Refraction, Ocular/physiology
Reproducibility of Results
Retrospective Studies
Visual Acuity/physiology

Figure

• 

  Fig. 1 Scatter plots to compare means for axial length measured with ultrasound and AL-scan. Axial length measurement by two methods showed a statistically significant relationship. USAXL = axial length measured with applanation ultrasound; ALAXL = axial length measured with AL-scan. r = 0.976, p < 0.01.

• 

  Fig. 2 Bland-Altman plots for assessing agreement of pairs of two methods. y = 0.012 X - 0.317; mean = -0.0334 ; mean +2 SD = 0.32508 ; mean -2 SD = -0.39188. The solid line represents the average mean difference (-0.0334) and the dotted line represents the 95 percentile confidence interval. The slope of regression line is 0.012 and represents low error between two methods and high reliability. In the scatter plot, most values are on the dotted line (±1.96 SD, -0.3919 to 0.3251), suggesting good comparability. SD = standard deviation; USAXL = axial length measured with applanation ultrasound; ALAXL = axial length measured with AL-scan.

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