[Calculation of intraocular lens power in surgical treatment of extreme hyperopia]

[Reasonability of accounting for gender in intraocular lens power calculation]

PURPOSE

The study assesses the influence of gender on the accuracy of intraocular lens (IOL) power calculation by formulas SRK/T, Barrett Universal II (BUII), Ladas super formula (LSF), Hill RBF (RBF) and Kane.

MATERIAL AND METHODS

The study enrolled 214 patients (106 men and 108 women) who underwent cataract phacoemulsification (PE). Optical biometry was performed on IOL-Master 500. IOL power calculation was performed either adjusting for gender (formulas SRK/T, BUII, LSF) or without such adjustment (formulas RBF, Kane). Calculation error (CE) was assessed one month after PE by comparing the achieved (autorefractometer Topcon-8800) and target spherical equivalent of refraction.

RESULTS

Significant differences were found in mean IOL CE with gender-unspecific formulas (SRK/T, BUII, LSF) and no differences in gender-specific calculators (RBF, Kane). The Kane formula demonstrated the lowest CE between men and women (-0.01±0.43 versus -0.09±0.41 D; p=0.158), while the SRK/T formula had the highest CE (0.02±0.46 versus -0.21±0.44 D, respectively; p<0.001). Presence of a significant correlation between CE and gender was found for all formulas except Kane (R2=0.005, p=0.158).

CONCLUSION

Patient's gender has a significant impact on IOL calculation accuracy. Using gender-responsive formulas could help achieve better refractive results with PE. The present study showed Kane formula to have the least CE dependence from gender. However, the CE difference (less than 0.25 D) was lower than the value of division (0.5D) in modern IOL models.

Effectiveness, Sensitivity, and Specificity of Intraocular Lens Power Calculation Formulas for Short Eyes

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Materials and Methods:

Results:

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Comparing the accuracy of new intraocular lens power calculation formulae in short eyes after cataract surgery: a systematic review and meta-analysis

PURPOSE

Calculating the intraocular lens (IOL) power in short eyes for cataract surgery has been a challenge. A meta-analysis was conducted to identify, among several classic and new IOL power calculation formulae, which obtains the best accuracy.

METHODS

All studies aiming at comparing the accuracy of IOL power calculation formulae in short eyes were searched up in the databases of PubMed, EMBASE, Web of Science and the Cochrane library from Jan. 2011 to Mar. 2021. Primary outcomes were the percentages of eyes with a refractive prediction error in ± 0.25D, ± 0.5D and ± 1.0D.

RESULTS

Totally 1,476 eyes from 14 studies were enrolled in comparison of 13 formulae (Barrett Universal II, Castrop, Haigis, Hoffer Q, Holladay1, Holladay2, Kane, Ladas Super Formula, Okulix, Olsen, Pearl-DGS, SRK/T and T2). Pearl-DGS had the highest percentage within ± 0.25D. In the ± 0.5D range, Pearl-DGS obtained the highest percentage again, and it was significantly higher than Barrett Universal II, Haigis, Hoffer Q, Holladay1, Holladay2 and Olsen (P = 0.001, P = 0.02, P = 0.0003, P = 0.01, P = 0.007, P = 0.05, respectively). In the ± 1.0D range, Okulix possessed the highest percentage, and it was significantly higher than Barrett Universal II, Castrop, Hoffer Q and Holladay2 (P = 0.0005, P = 0.03, P = 0.003, P = 0.02, respectively).

CONCLUSION

The new generation formulae, based on artificial intelligence or ray-tracing principle, are more accurate than the convergence formulae. Pearl-DGS and Okulix are the two most accurate formulae in short eyes.

[Alternative method of intraocular lens power calculation in eyes with short axial length]

PURPOSE

To develop an alternative method of intraocular lens (IOL) power calculation in eyes with mature cataract and axial length (AL) of less than 22.0 mm using modern formulas Barrett Universal II and Hill RBF.

MATERIAL AND METHODS

The study enrolled 41 patients (41 eyes) who underwent phacoemulsification (PE). Ultrasound biometry (Tomey Biometer Al-100) and keratometry (Topcon-8800) were used for IOL power calculation by SRK/T and Haigis formulas. To calculate IOL power by Barrett Universal II and Hill RBF formulas, 0.2 mm were added to AL measured with ultrasonography (retinal thickness). One month after PE, spherical equivalent of refraction was compared with target refraction (calculated by the formulas listed above), and based on that a conclusion was made on the accuracy of calculations.

RESULTS

Haigis formula was found to be the least accurate (IOL calculation error -0.39±0.79 D). The calculation error in SRK/T (0.04±0.79 D), Barrett Universal II (0.02±0.79 D) and Hill RBF (-0.05±0.73 D) formulas was much lower. However, among them Hill RBF had the lowest spread of the mean absolute IOL calculation error. Pairwise comparison revealed significant difference of mean IOL calculation error by Haigis formula versus the others. There was no significant difference in the following pairs: SRK/T - Barrett Universal II (p=0.855), and SRK/T - Hill RBF (p=0.167), but there was a significant difference (p=0.043) in the Barrett Universal II - Hill RBF pairdue to the tendency for slight hypermetropic calculation error in the former and the inherent slight myopic shift in the latter..

CONCLUSION

The proposed alternative method of IOL power calculation in eyes with mature cataract and short AL using modern formulas (Barrett Universal II and Hill RBF) shows higher accuracy compared to the formulas embedded in ultrasound biometer (SRK/T and Haigis), and can be recommended for use in everyday practice.

THE EXACTNESS OF INTRAOCULAR LENS POWER CALCULATION FORMULAS FOR SHORT EYES AND CORRELATION BETWEEN METHOD ACCURACY AND EYEBALL AXIAL LENGTH

PURPOSE

To compare the accuracy of intraocular lens power calculation formulas and to examine the correlation of this exactness with the axial length for eyes shorter than 22.00 mm Methods: The data of hyperopic patients who underwent uneventful phacoemulsification between October 2015 and June 2019 were reviewed. The intraocular lens power for each patient was calculated using 6 formulas (Holladay1, SRK/T, Hoffer Q, Holladay 2, Haigis and Barrett Universal II) before cataract surgery. Postoperative refraction was measured, and refractive prediction error was calculated 3 months after phacoemulsification. The correlation between axial length and absolute error was evaluated.

RESULTS

Fifty-six patients (62 eyes) whose ocular axial length ranged between 20.58 mm and 21.97 mm were included in the study. The Hoffer Q formula achieved the lowest mean absolute error of 0.09 (±0.08 D). A significant correlation for the Hoffer Q (&#961; = -0.329, p = 0.009) and the SRK/T (&#961; = 0.321, p = 0.011) formula was observed.

CONCLUSIONS

1. The Hoffer Q formula obtained the lowest absolute error and was recommended for intraocular lens power calculation for eyeballs with axial length shorter than 22.0 mm. 2. The correlation between axial length and absolute error is a factor which should be considered when calculating intraocular lens power.