Simple Nomogram for Calculating IOL Powers in Eyes After Previous Corneal Refractive Surgery
Purpose
The purpose of this study was to evaluate a quick, simple and accurate way to select the proper intraocular lens power for cataract surgery in eyes that have undergone previous corneal refractive surgery in which the ocular measurements prior to the corneal refractive surgery were unavailable.
Methods
Previous experience by one of the authors (MC) allowed the formulation of a nomogram table that was used for a prospective study of 50 eyes undergoing cataract surgery with a history of previous corneal refractive surgery (RK and LASIK). The ocular measurements prior to the corneal refractive surgery were unavailable. Optical biometry was used to measure the axial length and keratometry. The nomogram utilized the average keratometry measurements just prior to cataract surgery to adjust the intraocular lens power calculations from the SRK-T formula. Post operative uncorrected visual acuity and manifest refraction were used to assess the effectiveness of the nomogram.
Results
Twenty eight eyes (56%) saw 20/25 and forty seven eyes (94%) saw 20/40 or better post cataract surgery without correction. Results suggest that the nomogram can produce good uncorrected post op vision after cataract surgery in eyes that have had previous corneal refractive surgery and without the knowledge of the pre corneal surgery data.
Conclusion
This study demonstrates a simple and quick way to calculate intraocular lens powers in these difficult eyes with previous corneal refractive procedures even without data from the pre corneal surgery status.