LASIK and other refractive surgeries do not prevent cataract surgery. However, in cataract surgery, calculations are needed to determine the ideal power of the intraocular lens used to replace the cataract. These calculations depend on assumptions that are no longer valid after refractive surgery. As a result, targeting a certain vision outcome (such as not needing glasses to see far away) is harder.
Many formulas can be used to help with the changes due to refractive surgery. Although they are helpful, they are generally not very accurate. To improve the calculations, some formulas use the clinical information from the refractive surgery. However, most of the time, this information is not even available. The latest generation of formulas take advantage of the most accurate methods of measuring the power of the cornea, the front shell of the eye.
Some instruments can only measure the front surface of the cornea. Since this is changed in refractive surgery, it is difficult to determine the cornea’s true power. More advanced instruments can now also measure the back surface. The latest formulas utilize the information from both surfaces for the most accurate calculations.
Another way to improve the outcome of the calculations is to use the ORA intraoperative aberrometer. The eye can be thought of as needing a certain refractive power to see clearly. If the eye has too much or too little refractive power, images are blurry and the eye needs some sort of refractive correction, such as glasses, to bring images back in focus.