Clinical Comparison of Methods to Calculate IOL Power After Myopic LASIK and PRK
Narrative Responses:
Purpose
To convalidate on a larger sample the results of previous studies comparing different methods to calculate the intraocular lens (IOL) power in eyes who underwent myopic LASIK or PRK.
Methods
We prospectively analyzed 66 eyes that underwent cataract surgery after myopic PRK or LASIK. Eyes were classified as follows: Group 1 (preoperative corneal power (Kpre) available, refractive change known, n = 28), Group 2 (Kpre available, refractive change uncertain, n = 16), Group 3 (Kpre unavailable, refractive change known, n = 18), Group 4 (Kpre unavailable, refractive change unknown, n = 4). The IOL power was calculated according to the clinical history method and those by Awwad, Camellin, Date/Diehl/Miller, Feiz, Latkany, Masket, Rosa, Savini, Shammas, Seitz/Speicher, and Seitz/Speicher/Savini. The main outcome was the mean absolute error (MAE) in IOL power prediction.
Results
In Groups 1 and 2 the lowest MAEs were obtained with the Seitz/Speicher/Savini method (respectively 0.45 and 0.60 D), Seitz/Speicher method (respectively 0.56 and 0.61 D), Savini method (respectively 0.54 and 0.75 D), and Masket method (respectively 0.57 and 0.77 D). In Group 3, the lowest MAEs were obtained with the Masket method (0.69 D), Shammas No-History method (0.71 D), Seitz/Speicher/Savini method (0.82 D), and Savini method (0.92 D). In Group 4 the lowest MAE was obtained with the Shammas No-History method (0.72 D).
Conclusion
When Kpre is known, the method by Seitz/Speicher (with or without Savini’s adjustment) is the best solution to accurately calculate IOL power. When Kpre is unavailable, but refractive change is known, the Masket method is the most accurate solution. When no preoperative data are available, Shammas No-History method should be relied on.