Why LASIK complicates the calculation
Lens power is calculated from the eye's length and the cornea's curvature. Standard instruments measure the front of the cornea and estimate the back from it, using the fixed relationship between the two in a normal cornea. LASIK flattens the front surface and leaves the back unchanged, so that relationship no longer holds, and the instruments overestimate the cornea's power in a nearsighted LASIK eye. The result, if the surgeon uses a standard formula, is an implant that is too weak and a patient left farsighted after surgery.
How the calculation is corrected
- Post-refractive formulas, which are designed for corneas that have had laser surgery and use tomography that measures the back surface directly
- Your records: the prescription before LASIK and the amount treated improve some formulas, so bring them if you have them; modern formulas still give good results without them in most cases
- Intraoperative aberrometry, when appropriate, which measures the eye during surgery after the cataract is removed and confirms the lens power directly
- The Light Adjustable Lens, which is fine tuned after surgery so that any residual error is corrected in the lens itself
Choosing a lens after LASIK
Patients who had LASIK usually chose it because they wanted to be free of glasses, and they tend to want the same from cataract surgery. That is achievable, with two cautions. Multifocal lenses depend on a regular cornea, and a LASIK cornea with residual higher order aberrations may not suit them; extended depth of focus lenses are often more forgiving. And accuracy of the target matters more with these lenses, which is where the Light Adjustable Lens is frequently the recommendation.
The surgery itself
The operation is the same as for any cataract. The LASIK flap, even decades old, is very rarely affected by cataract incisions, which are made at the edge of the cornea. Recovery is the same. Dry eye, which LASIK patients are somewhat more prone to, is checked and treated before surgery because it affects both the measurements and comfort afterward.
Is this right for your eyes?
Nothing on this page is a diagnosis. Whether this is what is affecting your vision is decided by a full examination at one of our 4 offices: Pasadena, Huntington Beach, Woodland Hills and Beverly Hills.
About this content: This page was written with the assistance of AI tools and reviewed for medical accuracy by Dr. Bavand Youssefzadeh, DO. It is general information, not medical advice, and does not replace an eye examination. Individual results vary. Read our medical disclaimer.
