If, during cataract surgery, the decision is made to place the intraocular lens in the ciliary sulcus, rather than the capsular bag, a decrease in lens power is often necessary. This is because, as the optic is shifted more anterior (moved closer to the cornea), its “effective power” increases. The amount of this change is dependent on the “base power” of the intraocular lens. The greater the power, the greater the difference.
Below is a chart for which this calculation has been made over a standard range of base powers from +30.00 D to +5.00 D. The central corneal power is assumed to be in the normal range. The capsular bag effective lens position (also known as ACD) is assumed to be 5.20 mm (as with the popular Alcon MA60AC). Still, these numbers will work with almost any modern posterior chamber intraocular lens. The effective lens position for the ciliary sulcus is estimated to be 4.70 mm.
It is recommended that this information be available in the operating room as a handy reference for whenever this situation arises.
