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Steven Matthew Naids, Sarah Elise Brown, Bradford L. Tannen; Refractive Differences Among Intraocular Lens Formulas and Correlation With Outcomes in the Fellow Eye . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2973.
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Partial coherence interferometry (Zeiss IOL Master) selects lens power based on targeted postoperative spherical equivalents. Actual manifest refractive outcomes may differ from the targeted refractive error. Also, error may occur if the same biometry measurements are used in surgical planning of the second eye. This study investigates the accuracy of targeted versus refractive outcomes using SRK/T, SRKII and Holladay formulas, and whether a correlation exists between the first and second eye post-operative spherical equivalent prediction errors.
Retrospective review from January 2013 to September 2014 of 36 eyes of 18 patients that underwent bilateral subsequent phacoemulsification. Biometry from the first surgery was also used for the second eye. All surgeries were performed by the same surgeon, and all patients received an Alcon SN60WF PCIOL. The “refractive difference” was determined by the difference between the predicted and manifest spherical equivalent at one month. Refractive difference was determined for the SRK/T, SRKII, and Holladay formulas using the same IOL power that was implanted. Linear regression was used to investigate the relationship between the error in the first and second eye for each formula.
The mean refractive differences at one month for the first and second eye, respectively, for each formula were as follows: SRK/T (0.18+/-0.42, 0.04+/-0.431), SRKII (0.14+/-0.57, -0.001+/-0.56), Holladay (0.23+/-0.41, -0.02+/-0.46) . While refractive difference in the first eye was not related to the second eye using the SRKT and Holladay formulas (p= 0.280, p=0.140, respectively), refractive difference in the first eye was statistically correlated with that of the second eye using SRKII (p=0.004).
The results of this study suggest that the amount of refractive difference at one month after phacoemulsification in the first operative eye has a significant correlation with the second eye when using SRKII. This relationship was not found to exist for SRK/T and Holladay. The mean SRKII refractive differences at one month for both eyes were closer to the targeted spherical equivalent than the other two formulas in this cohort, although results were similar among the formulas. Confirmation of this statistical corelation in a larger study is warranted, and may be a consideration for adjusting the power of the lens used in the second eye using SRKII.
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