How is lens power determined before cataract surgery?

The most important measurements we take are the length of the eye and the shape (curve) of the cornea (clear dome-shaped window at the front of the eye). These measurements, plus a few other factors and the features of your chosen intraocular lens, are used in various formulas to choose the right power of lens. These formulas give you and your ophthalmologist a choice of power. The calculations have gotten better and are based on mathematics and population data. They are extremely accurate but not 100%. This is because each eye is unique and may have characteristics that defy the assumptions of the formulas. Sometimes we can anticipate this and sometimes we can’t. There is art and science to this. We don’t always get it exact, but nearly all patients are happy with their vision.