At Liva Eye Center the Zeiss IOLMaster 700 is used to calculate IOL power in most patients. The IOLMaster uses a laser to measure the axial length of the eye to the hundredth of a millimeter. Combined with measurements of the corneal curvature and the anterior chamber depth the IOL power to achieve a certain refractive outcome is calculated. The IOLMaster 700 is the first biometry instrument to measure the the curvature of the back surface of the cornea. It combines the measurement from the anterior curvature of the cornea and the posterior curvature to give a mare accurate measure of the total astigmatism of the cornea. The power and axis of placement of toric intraocular lenses are more accurate incorporating this new technology resulting in better refractive outcomes.
In cases where the cataract is too dense to use the laser for measurements immersion ultrasound is used. Immersion ultrasound is less accurate than Laser biometry which is why I sometimes use the IOLmaster in patients with early cataracts that I predict may progress to the point that I may not be able to perform laser biometry. In those cases I perform laser biometry and do not charge the patient or the insurance company until I actually plan doing cataract surgery on the patient. In the era of premium lenses accurate IOL calculations are extremely important since the performance of those lenses requires measurement as accurate as possible. Studies have shown that even with the best technologies employed that on some occasions the calculations fail to provide the desired outcome due to variations in the biological system. For instance the final IOL position in the eye can only be estimated and the final IOL position can alter the focus of the eye significantly and result in unexpected refractive results.