Axial length measurements before and after removal of silicone oil: a new method to correct the axial length of silicone-filled eyes for optical biometry.

A total of 67 eyes of 67 patients that have undergone vitrectomy and silicone oil tamponade for rhegmatogenous retinal detachment were included in this prospective clinical study. We measured the axial length (AL) and the anterior chamber depth (ACD) with A-mode ultrasonography and IOL Master before and after removal of silicone oil. Phase refractive indices of silicone oil at different wavelengths from 400 nm to 1000 nm were measured with an Abbe refractometer and a series of equations were derived to adjust the AL values obtained with the IOL Master in silicone-filled eyes. The instruments showed good agreement between the AL values measured before and after removal of silicone oil. The ACD values obtained with A-mode ultrasonography were lower than the values obtained with the IOL Master ( p < 0.01). The AL values obtained with the IOL Master after removal of silicone oil were lower than the values obtained preoperatively ( p < 0.01). The AL values obtained with the IOL Master after adjustment are more accurate than A-mode ultrasonography in silicone-filled eyes. [ABSTRACT FROM AUTHOR]