Volumes of Choroidal Nevi on Widefield Optical Coherence Tomography Compared to Calculations Based on Ultrasound Measurements.

INTRODUCTION

This study aimed to evaluate choroidal nevi (CN) volume as assessed by widefield optical coherence tomography (WF-OCT) and by ultrasound (US)-based mathematical approximations.

METHODS

In a prospective, exploratory study, CN of consecutive patients were imaged with WF-OCT (VG 200D, Intalight Inc., San Jose, California, USA) and US (Quantel Absolu, Cournon, D'Auvergne Cedex, France). Volume was assessed by CN annotation on 64 B-scans on WF-OCT and two approximations based on US measurements (thickness, largest and perpendicular basal diameter (LBD; PBD)): (a) π/6 × thickness × LBD × PBD and (b) 2π/3 × [(LBD + PBD)/4]2 × thickness.

RESULTS

Eighteen nevi of 18 patients were included in the study. Mean volume evaluated on WF-OCT was 15.1 ± 24.1 mm3. US approximations resulted in (a) 23.0 ± 35.0 mm3 and (b) 23.5 ± 35.5 mm3. Intraclass correlation coefficients showed very good agreement between WF-OCT and US measurements (a) of 0.947 (CI 0.860-0.980) and (b) of 0.945 (CI 0.853-0.979). Stepwise backward elimination multivariable linear regression showed an association between difference of volume measurements and lesion thickness and LBD for approximations (a) and (b).

CONCLUSION

WF-OCT and US-based approximations show good interdevice reliability for CN volume in this exploratory study. Thickness and LBD have significant impact on discrepancy of volume measurements with a tendency that small CN are underestimated and large CN are overestimated with US. This potentially limits interchangeable use of US and WF-OCT.