Before inserting an artificial eye lens – also known as an intraocular lens (IOL) – the required refractive power of the artificial lens must be precisely calculated. This is meant to achieve optimal visual performance with the desired refractive power, (matching the other eye), later. This measurement used to be carried out with ultrasound. Today it is more accurately measured mostly with laser light. The measurement determines the axial length, the corneal radii and, if necessary, the anterior chamber depth of the eye.