Analysis of Factors that Influence on Accuracy of Intraocular Lens Power Calculation

ABSTRACT

PURPOSE: To investigate which factors primarily influence refractory errors between various formulas used to calculate intraocular lens (IOL) power. METHODS: Records of 266 eyes of 191 patients who underwent uneventful cataract surgery were reviewed retrospectively. IOL power was determined using SRK/T, HofferQ (H/Q), Master SRK/T (M/T), Master HofferQ (M/Q), Master Holladay (M/Hol), and Master Haigis (M/Hai). The mean absolute error (MAE) of each formula was compared; MAE was defined as the difference between the postoperative spherical equivalence (SE) determined 1 month after surgery and the predicted SE. Factors that could have influenced interformula refractive errors were analyzed. Patients were divided into 3 groups based on average keratometric value (Kavg) and the inter-group differences of the AE of each formula were analyzed. Effects of corneal curvature on changes in AE of each formula were evaluated by linear regression. RESULTS: The MAE was minimized in the M/T formula, followed by the M/Hol, M/Hai, SRK/T, H/Q, and M/Q formulas. Interformula MAE differences were not statistically significant. Kavg and AXL were significantly influenced by the different predictive values between formulas in univariate analysis, but only AXL was significant in multivariate analysis. The AE in each formula among the 3 groups according to keratometry was significantly different in SRK, M/Hol, and M/Hai. Linear regression analysis showed a significant negative correlation between Kavg, AE of SRK/T and the MHai formula. In particular, this effect was more pronounced in those with short AXL (<22.5 mm). CONCLUSIONS: There were no significant MAE differences between formulas. AXL was a significant factor that influenced the differences between formulas. SRK/T and M/Hai may be affected by outside the normal range of corneal curvatures.