AIM:To evaluate the accuracy of modified sound speed for the measurement of eye axis and the power of intraocular lens(IOL) in silicone oil-filled eye.·METHODS:Twenty-four cases with cataract after silicone oil tamponade from 2003 to 2008 in our hospital were included.The eye axis length were measured with A-ultrasonic scan and calculated by the sound speed modified formula.The power of IOL were then calculated through SRK II formula.All cases underwent the operation of silicone oil removal combined with phacoemulsification and IOL implantation.3 months after surgery all eyes were reexamined and the actual axial length were again measured.The eye axis length and the refraction state were compared before and after the operation.·RESULTS:The eye axis length was 25.25±0.65mm before silicone oil tamponade and 24.80±0.67mm after the operation.And the postoperative eye axis length measurements showed no statistical significance compared with the preoperative measurement.The mean difference of the refraction state before and after the operation was 1.50±0.40D,and the difference was not significant.·CONCLUSION:Eye axis lens measurement with A-ultrasonic scan by modified sound speed shows better clinical practicability in silicone oil-filled eyes than traditional manual counting method.