J Korean Ophthalmol Soc.  2018 Jul;59(7):629-636. 10.3341/jkos.2018.59.7.629.

Comparison of Axial Length and Postoperative Refraction between Applanation Ultrasonography and Low-coherence Reflectometry

• Lee YP
• Shin YJ
• Yi K

• KMID: 2416265
• DOI: http://doi.org/10.3341/jkos.2018.59.7.629

Abstract

PURPOSE
To compare axial length applanation ultrasonography (A-scan) (CineScan B-Scan; Quantel Medical, Bozeman, MT, USA) and low-coherence reflectometry (Lenstar LS900®; Haag-Streit, Bern, Switzerland), the accuracy of the predictive postoperative refraction of both instruments, and the intraocular lens (IOL) calculators.
METHODS
A total of 250 eyes of 191 patients who received cataract surgery were included in the study. The axial length was measured by the A-scan and Lenstar LS900®. The SRK-2, SRK/T, and Olsen formulas were used to calculate the IOL power, and the difference between the predictive and actual postoperative refractions after 6 weeks and the probability that they were within 0.25 diopters (D) and 0.5 D were compared.
RESULTS
The mean axial lengths measured by the A-scan and Lenstar LS900® were 23.42 ± 0.94 mm and 23.55 ± 0.95 mm, respectively, which showed a statistically significant difference (paired t-test, p = 0.000). When comparing the difference between the predictive and actual postoperative refractions, the results of the A-scan using the SRK-2 and SRK/T formulas were significant toward the hyperopia, and the results of the Lenstar LS900® using the SRK-2, SRK/T, and Olsen formulas were significant toward the myopia (paired t-test, p = 0.001 and p < 0.001, respectively). When comparing the mean absolute difference between the two refractions and the probability that they were within 0.25 D and 0.5 D, the Lenstar LS900® using the Olsen formula significantly showed the highest accuracy (McNemar test, p = 0.045 and p = 0.002; p = 0.010 and p = 0.002, respectively).
CONCLUSIONS
The A-scan using the SRK-2 and SRK/T formulas showed that the actual postoperative refraction was more hyperopic than the predicted refraction, whereas the Lenstar LS900® resulted in more myopic findings. The accuracy of predictive postoperative refraction was highest with the Lenstar LS900® using the Olsen formula.

Keyword

Applanation ultrasonography; Axial length; Cataract surgery; Low-coherence reflectometry; Postoperative refraction

MeSH Terms

Cataract
Humans
Hyperopia
Lenses, Intraocular
Myopia
Ultrasonography*

Figure

• 

  Figure 1. Correlation between biometric data (axial length, keratometry) measured by Lenstar LS900® and other devices (Pearson correlation analysis). Axial length measured by Lenstar LS900® and A-scan (A). Keratometry measured by Lenstar LS900® and autokeratometer (B). r = Pearson correlation coefficient.

• 

  Figure 2. Bland-Altman plot of axial length and keratometry. Bland-Altman plot of axial length between A-scan and Lenstar LS900® (A), keratometry between autokeratometer and Lenstar LS900® (B). LOA = limit of agreement.

• 

  Figure 3. Comparisons of accuracy of predictive postoperative refraction by mean prediction error (A), mean absolute error (B). ‘A-scan (SRK-2/T)’ is ‘measurement of A-scan using SRK-2 and SRK/T formulas’, ‘Lenstar (SRK-2/T)’ is ‘measurement of Lenstar LS900® using SRK-2 and SRK/T formulas' and ‘Lenstar (Olsen)’ is ‘measurement of Lenstar LS900® using Olsen formula’. Bold line in gray box means ‘median value’, bottom line of gray box means ‘first quartile’, top line of gray box means ‘third quartile’, lower end of vertical line means ‘minimum value’, and upper end of vertical line means ‘maximum value’. * p < 0.05, Statistically significant (Paired t-test).

• 

  Figure 4. Comparisons of accuracy using probability within 0.25 D and 0.5 D. Comparisons of probability that the difference between the predictive and actual postoperative refraction is within 0.25 D (A) and within 0.5 D (B). * p < 0.05, Statistically significant (McNemar test).

Reference

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