Agreement and relationship between ultrasonic and partial coherence interferometry measurements of axial length and anterior chamber depth

Amany R Wissa, Sherein S Wahba, Maged M Roshdy
Ain Shams University and National Eye Hospital, Cairo, Egypt

Purpose: To find the relationship between axial length (AL) and anterior chamber depth (ACD) measurements, using partial coherence interferometry (PCI) and A-scan ultrasonography (US).
Setting: National Eye Hospital, Cairo, Egypt.
Method: Retrieving and comparing biometric data from the files of 163 consecutive patients seeking cataract extraction by PCI (IOLMaster) and US (Sonomed).
Results: AL measured using US range from 20.93 to 33.17 mm (mean ± SD = 24.45 ± 2.73 mm). AL measured by PCI range from 20.90 to 33.27 mm (24.05 ± 2.76 mm). The range of ACD measured by US was 2.09 to 4.48 mm (3.32 ± 0.46 mm). The range of ACD measured by PCI was 2.15 to 4.29 mm (3.31 ± 0.45 mm). There is very high agreement between both methods; the intraclass correlation coefficient = 0.999 for AL, and 0.966 for ACD measurements. A linear regression model of two formulae fits the AL values (one for eyes longer than 29 mm, and the other for the shorter eyes), with no significant departure from linearity (P > 0.1). One formula fits the ACD values with significant departure from linearity (P < 0.05).
Conclusion: Both US and PCI methods for measurements of AL and ACD are highly correlated. Therefore, the value of AL measured by one method can be predicted, with high accuracy, from the other method.

Keywords: axial length, anterior chamber depth, A-scan US, partial coherence interferometry