Comparing The Accuracy Of Intraocular Lens Calculation Formula Of High Myopia Complicated With Cataract

Objective: to compare the accuracy of different intraocular lens formulas in predicting postoperative diopter of high myopia complicated with cataract.Methods: Fifty-eight patients（87 eyes）with highly myopic cataract who routinely underwent cataract extraction combined with intraocular lens（IOL）implantation from October 2019 to October 2021 at our ophthalmology hospital were collected.Pre-operative completion of the patient’s ocular biology using the IOL Master 700,according to the Axial length（AL）,patients were divided into group A: 26 mm ≤ AL <28 mm（30 eyes）,group B: 28 mm ≤ AL < 30 mm（23 eyes）,and group C: AL ≥ 30 mm（34 eyes）.According to the Keratometry（K）,patients were divided into group D: K <43.0D（18 eyes）,group E:43D ≤ K ≤ 44.0D（26 eyes）,group F:44.0D < K ≤ 45.0D（19eyes）,group G: K > 45.0D（24 eyes）.According to anterior chamber depth（ACD）,patients were divided into Group H: ACD ≤ 3.2 mm（26 eyes）,Group I: 3.2 mm < ACD≤ 3.5 mm（31 eyes）,and Group J: ACD > 3.5 mm（30 eyes）.The same type of IOL（AMO Sensar AR40e）was used in this study,the theoretical predicted refraction is obtained by substituting the implanted IOL degree into each of the five different IOL calculation formulas,actual refractive error measured at 3 months postoperative follow-up,calculate the mean absolute refractive error based on the difference between the preoperative theoretical refraction and the actual postoperative refraction for each formula（actual postoperative refraction-theoretical predicted refraction）.The percentage of MAE within ±0.25 D,±0.50 D,±1.00 D,1.50 D,and ±2.00 D was calculated for each formula.Finally,the correlation between MAE and AL,K,and ACD for the five calculated formulas was evaluated.Results: The Overall MAE of the five formulas in order of smallest to largest are Barrett Universal II（0.41 ± 0.36）D,Haigis（0.58 ± 0.54）D,SRK/T（0.72 ± 0.59）D,Holladay 2（0.88±0.61）D,and Hoffer Q（1.11±0.69）D.The differences between the mean absolute refractive error of the five calculation formulas are statistically significant（P< 0.05）.The percentage of Barrett Universal II formulas within ±0.25 D,±0.50 D,±1.00 D,1.50 D,and ±2.00 D prediction errors were all highest,with a percentage of 95% within 1.00 D error,much higher than Haigis（78%）,SRK/ T（68%）,Holladay 2（58%）,Hoffer Q（44%）,and 100% for both the Barrett Universal II and Haigis formulas within the 2.00 D error range.In groups A,B,and C of axial length,the Barrett Universal II formula MAE was the lowest in all cases,with（0.28 ± 0.25）D,（0.44 ± 0.49）D,and（0.54 ± 0.31）D in that order,followed by Haigis,SRK /T,and Holladay 2,with Hoffer Q having the highest MAE.The differences between the mean absolute refractive error of the five calculation formulas are statistically significant（P<0.05）.In groups D,E,F,and G,the Barrett Universal II formula had the lowest MAE,in order of（0.29±0.23）D,（0.40±0.30）D,（0.34±0.29）D,（0.57±0.48）D,followed by Haigis,SRK/T,Holladay 2,and the highest MAE for Hoffer Q in that order.The differences between the mean absolute refractive error of the five calculation formulas are statistically significant（P < 0.05）.In groups H,I,and J,the Barrett Universal II formula had the lowest MAE,in order of（0.40±0.29）D,（0.46±0.48）D,and（0.37±0.26）D,followed by Haigis,SRK/T Holladay 2,and the highest MAE for Hoffer Q.The differences between the mean absolute refractive error of the five calculation formulas are statistically significant（P< 0.05）.Correlation analysis showed that the mean absolute error of the five formulas was positively correlated with axial length（P<0.05）,but not with anterior chamber depth（P>0.05）.The postoperative refractive state of the five calculated formulas drifted toward hyperopia,and the difference between the preoperative theoretical reserved refraction and the postoperative actual refraction was statistically significant（P< 0.05）,and the hyperopic error increased with the increase of the eye axial length.The flat corneal group（K < 43.0D）was more prone to hyperopic error compared to the steep corneal group（K > 45.0D）,and this effect was more significant for the SRK/T formula（P < 0.05）.Conclusions:1.The Barrett Universal II formula has the smallest prediction error compared to the Haigis,SRK/T,Holladay 2,and Hoffer Q formulas.Therefore,the Barrett Universal II formula can be considered a more reliable formula for high myopia complicated with cataract.2.The postoperative refractive errors of the five calculation formulas increased with the increase of the axial length,and the Barrett Universal Ⅱ formula was least affected and had higher clinical value for eyes with an axial length of more than30mm.3.Corneal refractive power is another factor that reduces the accuracy of intraocular lens formula prediction.When the corneal refractive power is between 43.0-45.0D,it has no significant effect on the accuracy of the calculation formula to predict postoperative refractive power.When it is outside this range,it will lead to an increase in postoperative refractive error,and a flat cornea is more prone to hyperopic error than a steep cornea,and the effect is more significant for the SRK/T formula.4.The change of anterior chamber depth has no significant effect on the accuracy of the calculation formula of intraocular lens power.5.The refractive states of the five formulas showed hyperopia drift after surgery.With the increase of the axial length,the degree of hyperopic drift became more obvious,but the Barrett Universal II formula was least affected by the change of the axial length,and the postoperative refractive status was the most stable.