Comparison of axial length, intraocular lens power and refractive results using optical and ultrasound biometry

Aims: The aim of the study was to determine whether a new non-contact partial coherence interferometry method utilized by the Nidek-AL Scan agrees sufficiently with applanation ultrasound A-scan technique in intraocular lens power calculation to replace it. Methods: This was a prospective study of 150 eyes of 125 patients who underwent cataract surgery with the Nidek AL Scan and ultrasound biometry. The intraocular lens power AL and ACD were compared between two methods with Pearson correlation and Bland-Altman analysis. The mean difference between final spherical equivalent refraction and the prediction with each technology was compared. Results: On average the axial lengths measured by the Nidek AL-Scan were longer by 0.11 ± 0.13 mm compared the ultrasound biometry. (p<0.001). Pearson correlation analysis showed very high correlation between 2 devices for AL and IOL power (r>0.90, p<0.05). and high correlation for ACD. On Bland-Altman analysis 95% limits of agreement for all parameters were within clinically acceptable limits and there was good agreement between 2 devices. Mean absolute error when SRKT formula for AL-Scan was 0.20 ± 0.17 D whereas for US 0.29 ± 0.25 D (p<0.001) Conclusion: The intraocular lens power and AL derived from both groups were similar. The agreements between them were high. Two techniques may be used interchangeably.