PurposeTo evaluate and compare the accuracy of six different formulas (EVO 2.0, Kane, SRK/T, Barrett Universal II, Haigis and Olsen) in intraocular lens (IOL) power calculation for extremely long eyes.MethodsRetrospective case-series. 73 eyes with axial length (AL) ≥ 29.0 mm and 920H IOL implantation were included. Prediction errors (PE) were calculated and compared between different formulas. Multiple regression analysis was performed to investigate factors associated with the PE.ResultsThe Kane formula had mean prediction error close to zero (-0.01 D, P = 0.841), whereas the EVO 2.0, SRK/T, Barrett Universal II, Haigis and Olsen formulas produced hyperopic outcomes (all P < 0.001). The median absolute error produced by the EVO 2.0, Kane, Barrett Universal II and Olsen formulas showed no significant difference (0.33 D, 0.30 D, 0.29 D, 0.34 D, respectively, pairwise comparison P > 0.05), but was significantly lower than that of the SRK/T and Haigis formulas (0.85 D, 0.80 D, respectively, pairwise comparison P< 0.001). The accuracy of the SRK/T formula in extremely myopic eyes was affected by the AL, suggesting that a longer AL was always associated with a hyperopic surprise and a shorter AL was always associated with a myopic surprise, whereas the accuracy of other formulas was less affected by the AL.ConclusionsFor cataract patients with axial length greater than 29.0 mm, the accuracy of the EVO 2.0, Kane, Barrett Universal II and Olsen formulas is comparable and significantly better than that of the SRK/T and Haigis formulas.
Purpose: Hyperopic surprises tend to occur in axial myopic eyes and other factors including corneal curvature have rarely been analyzed in cataract surgery, especially in eyes with long axial length (≥ 26.0 mm). Thus, the purpose of our study was to evaluate the influence of keratometry on four different formulas (SRK/T, Barrett Universal II, Haigis and Olsen) in intraocular lens (IOL) power calculation for long eyes.Methods: Retrospective case-series. 180 eyes with axial length (AL) ≥ 26.0 mm were divided into 3 keratometry (K) groups: K ≤ 42.0 D (Flat), K ≥ 46.0 D (Steep), 42.0 < K < 46.0 D (Average). Prediction errors (PE) were compared between different formulas. Multiple regression analysis was performed to investigate factors associated with the PE.Results: The mean absolute error was higher for all evaluated formulas in Steep group (ranging from 0.66 D to 1.02 D) than the Flat (0.34 D to 0.67 D) and Average groups (0.40 D to 0.74D). The median absolute errors predicted by Olsen formula were significantly lower than that predicted by Haigis formula (0.42 D versus 0.85 D in Steep and 0.29 D versus 0.69 D in Average) in Steep and Average groups (P = 0.012, P < 0.001, respectively). And the Olsen formula demonstrated equal accuracy to the Barrett II formula in Flat and Average groups. The predictability of the SRK/T formula was affected by the AL and K, while the predictability of Olsen and Haigis formulas was affected by the AL only. Conclusions: Steep cornea has more influence on the accuracy of IOL power calculation than the other corneal shape in long eyes. Overall, both the Olsen and Barrett Universal II formulas are recommended in long eyes with unusual keratometry.
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