[Clinical study of intraocular lens power calculation methods after cornea refractive surgery]

Abstract

Objective: To evaluate the results of cataract surgery in myopia patients after laser in situ keratomileusis (LASIK) and to compare the predictability of various methods of intraocular lens (IOL) power calculation.

Method: Seventeen cases (24 eyes) who had LASIK for myopia were divided into two group by with or without history of corneal power data. Corneal power was obtained by autokeratometry, corneal topography, Pentacam and IOL Master. The IOL power was calculated with the clinical history method, Feiz-Mannis formula, Feiz-Mannis method and other methods. Postoperative final refraction and the deviation of the final spherical equivalent (SEQ) from the refractive target were measured 3 month after the surgery. Two sample t-test, linear correlation and regression analysis, paired t-test and Bland-Altman method of agreement were used to analyze these data.

Results: In the group with history data, the mean corneal power was (43.28 ± 1.21) D and the mean SEQ was (-15.33 ± 4.36) D before the LASIK surgery. In the group without history data, the mean SEQ was (-10.11 ± 3.12) D. Before cataract surgery, the mean corneal power was (36.96 ± 2.07) D and (36.85 ± 1.40) D in these two groups. The mean arithmetic refractive prediction error after cataract surgery was (-0.66 ± 1.27) D and (-0.47 ± 0.82) D in these two groups, respectively. Data calculated by using Hamed-Wang-Koch method, Masket Formula, Koch/Maloney method, Shammar method and Pentacam ERK method were lower than the emmetropic IOL power. Data calculated by using Feiz-Mannis Formula, Latkany Method, Savini method, Armberri Double K method were overestimated. The mean arithmetic errors of clinic history method, Corneal Passby Method and Haigis-L Formula were not significantly different from the predict refraction (P = 0.364, 0.318 and 0.069; t = 0.956, -1.057 and -1.911, respectively). There was strong correlation between the value calculated by using Feiz-Mannis Method or Haigis-L Formula and the true power (r = 0.921, 0.915; P = 0.000 and 0.000, respectively). But none of the values calculated by these method could fully agree with the true value.

Conclusions: IOL power should be calculated accurately to avoid undercorrection. We recommend the combination of clinical history method, Feiz-Mannis Method, Corneal Passby Method and Haigis-L Formula for the calculation of IOL power.