Comparison Of IOL-Master And A-scan For Intraocular Lens Power Calculation

Objective To compare the accuracy of IOL-Master and A-scan in biometry and intraocular lens power calculation.Methods 96 patients(98 eyes)with age-related cataract patients(91 patients(93eyes)actual analysis).they were divided into three groups by axial length: short eye axial group(L < 23 mm) 22 eyes, moderate ocular axial length group(23 mm≤ L≤ 26 mm) 49 eyes,long eye axial group(L> 26 mm) 22 eyes;Before surgery,axial length, corneal curvature and anterior chamber depth were measured with IOL-Master,A-scan and corneal curvature-apparatus; IOL power was calculated according to the SRK-T or SRK-II formula.Cataract surgery,phaco-emulsification and phaceetomy was performed in all patients and foldable lens were implanted according to the results of A-scan method,;Refractive outcomes were followed up three month after operation, and specification of main optometry in all patients;Absolute refractive error(MAE) was calculated and analyzed.Results1 Short eye axial group(L < 23 mm):(22.69±0.30) mm vs(22.55±0.36)mm,moderate ocular axial length group(23 mm≤ L ≤ 26 mm):(24.01±0.69) mm vs(23.84±0.65)mm, long eye axial group(L > 26 mm):(30.12±1.62) vs(29.26±1.45)mm. There were some significant differences among three groups in axial length measurement between IOL-Master and A-scan(P<0.01).Pearson correlation analysis was carried out on the short axial group, r = 0.914, P < 0.01, the axial length by two methods of measuring were significantly positive correlation.2 Short eye axial group(L < 23 mm):(44.40±2.39) D vs(43.94±2.18) D,moderate ocular axial length group(23 mm≤ L ≤ 26 mm):(43.68±1.30) D vs(43.25±1.25) D, long eye axial group(L > 26 mm):(45.09±1.24) D vs(44.53±1.16) D.There were some significant differences among three groups in corneal curvature measurement between IOL-Master and A-scan(P<0.01).3 In anterior chamber depth measurement: Short eye axial group(L < 23mm):(2.89±0.37)mm vs( 2.96±0.40) mm, moderate ocular axial length group(23mm≤ L ≤ 26 mm),(3.15±0.38)mm vs(3.24±0.37)mm, long eye axial group(L >26 mm):(3.30±0.33)mm vs(3.13±0.37)mm. There was no significant difference in Short eye axial group(L < 23 mm) and moderate ocular axial length group(23 mm≤L ≤ 26 mm) between IOL-Master and A-scan(P> 0.05).There were some significant differences in long eye axial group(L > 26 mm) between IOL-Master and A-scan(P<0.01).Pearson correlation analysis was carried out on the moderate ocular axial length group, r = 0.790, P < 0.05, there is statistical significance,;short axial group, r= 0.605, P < 0.05, there is statistical significance, two measurement methods are consistent.4 Short eye axial group(L < 23 mm): The absolute refractive error(MAE) of IOL-Master were between(0-2.5)D, And the absolute refractive error(MAE) of A-scan were between(0-3)D.The percentage of absolute postoperative refractive error(≤0.5D、≤1.0D、≤2.0D) in IOL- Master is 27.27%、81.81% and 90.90%;The percentage of absolute postoperative refractive error(≤0.5D、≤1.0D、≤2.0D) in A-scan is 18.18% 、 63.64% and 72.27%. There was no statistically significant difference(≤0.5D、≤1.0D、≤2.0D) in chi-square test.Moderate ocular axial length group(23 mm≤ L ≤ 26 mm) : The absolute refractive error(MAE) of IOL-Master were between(0-3.5)D, And the absolute refractive error(MAE) of A-scan were between(0-4)D.The percentage of absolute postoperative refractive error(≤0.5D、≤1.0D、≤2.0D) in IOL- Master is 53.06%、61.22% and 91.84%; The percentage of absolute postoperative refractive error(≤0.5D、≤1.0D、≤2.0D) in A-scan is 44.90%、46.94% and 79.59%..There was no statistically significant difference(≤0.5D、≤1.0D、≤2.0D) in chi-square test.Long eye axial group(L> 26 mm): The absolute refractive error(MAE) of IOL-Master were between(0-5)D, And the absolute refractive error(MAE) of A-scan were between(0-6)D.The percentage of absolute postoperative refractive error(≤0.5D、≤1.0D、≤2.0D) in IOL- Master is 45.45%、72.72% and 86.36%;The percentage of absolute postoperative refractive error(≤0.5D、≤1.0D、≤2.0D) in A-scan is 13.63% 、 18.18% and 54.54%.There was no statistically significant difference(≤0.5D) in chi-square test(χ2=3.27, P>0.05); There was a statistically significant difference(≤1.0D) in chi-square test(χ2=8.64,P<0.01);There was no statistically significant difference(≤2.0D) in chi-square test(χ2=2.77,P>0.05).Conclusion:1 In the case of refractive media turbidity is lighter,The accuracy of measuring eye axial by IOL-Master were higher than the date by A-scan.The longer the eye axial,the more obvious difference; And there were positively correlated with eye axial.2 The measuring anterior chamber depth by IOL-Master were deeper than the date of A-scan in long eye axial. There was no significant difference in Short eye axial group and moderate ocular axial length group.3 The measuring corneal curvature of IOL-Master were bigger than the date of A-scan among three groups.4 Artificial crystal degree: The accuracy of measuring intraocular lens degree by IOL-Master were higher than the date by A-scan in long eye axial.5 IOL-Master is a accurate, non-contact, safe and reliable tool of IOL power calculation; And it is easy to operate.