Abstract
Purpose :
It was addressed that deviations from the assumed relation between axial length (AL) and keratometry (K) is one of causes of an unexpected refractive errors in long eyes with the use of the 3rd generation formulas. This study evaluated the effect of the proportion between AL and average K on 3 intraocular lens calculations.
Methods :
This retrospective case series reviewed clinical records of eyes that had AL of 26.0mm or longer and underwent cataract surgery with intraocular lens implantations. Preoperative biometry data was measured using a Lenstar® LS-900 (Haag-Steit). Prediction errors in the use of the SRK/T , Haigis and Barrett Universal II (Barrett U II) formulas were obtained from manifest refraction spherical equivalent 1 month postoperatively. The effects of proportion of AL to K (AL/K) were examined using step-wise multiple regression analysis.
Results :
There were 49 long eyes of 49 patients. The mean prediction errors with the uses of the SRK/T, Haigis and Barrett U II were 0.55D, 0.38D and 0.33D, respectively, and Barrett UII was significantly better than the SRK/T (P=0.0071, the Holm multiple comparison). The prediction errors associated with AL in the use of the SRK/T (P = 0.004, R2 = 0.14) and Haigis (P = 0.021, R2 = 0.11), however, there was no association with the Barrett UII. Step-wise multiple regression analysis resulted that the AL/K was not significant factor, except for the use of the SRK/T was the AL/K (P <0.001, R2 = 0.25). With the regression equation, the prediction errors with the use of the SRK/T were well represented (100% within ±1.00 D of differences). In the use of the Haigis, multiple regression analysis resulted that the AL was a significant factor (P = 0.021, R2 = 0.11).
Conclusions :
The refractive error in the use of the SRK/T for long eyes was caused by alternation of the proportion between the AL and K. It was suggested that Barrett UII and Haigis which are not influenced by the proportion are suitable for long eyes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.