Intraocular Lens Constant Optimization

Objective:1. To calculate optimized intraocular lens constant and to evaluate the influence of optimized intraocular lens constant on the refractive prediction after cataract surgery. 2. To calculate personalized intraocular lens constant and to evaluate the clinical significance of personalized intraocular lens constant. 3. To calculate long eye optimized intraocular lens constant and to evaluate the clinical significant of long eye optimized intraocular lens constant.Methods:1. Subjective postoperative refraction of 150 patients who were diagnosed with age-related cataract and had been implanted intraocular lens SN60 WF were collected three months later. The optimized intraocular lens constant A, surgery fact(SF), post-surgery anterior chamber depth(p ACD) were calculated by using the third IOL power calculator formulas SRK/T、Holladay I、 Hoffer Q combine with axial length(AL), keratometry, anterior champer depth(ACD) measured by Lenstar900 and IOL power implanted. Refractive outcomes using optimized IOL constants were re-calculated by separate or combination of SRK/T、Holladay I、 Hoffer Q. These optimized IOL constants and constant actually used were then used to calculate the theoretical prediction of postoperative refractive outcomes that would have been achieved if they had been used in all cases. Associated mean absolute errors(MAE) and mean error(ME) in deviation from the predicted postoperative refraction as well as the percentage of eyes within ±0.25 D, ±0.50 D, and ±1.00 D of the target refraction were calculated and compared. 2. The 192 eyes were divided into three groups by the surgeon. Group 1, 2, 3 has separate 79, 68, and 45 eyes included. The personalized intraocular lens constant A, SF, p ACD of each group 1,and 2 were calculated by using the third IOL power calculator formulas SRK/T、Holladay I、 Hoffer Q combine with axial length, keratometry, anterior depth measured by Lenstar900 and IOL power implanted. As for group 3, only personalized p ACD was calculated. These personalized constants used were then used to calculate the theoretical prediction of postoperative refractive outcomes that would have been achieved if they had been used in all cases. Associated mean absolute errors(MAE) and mean error(ME) in deviation from the predictedpostoperative refraction as well as the percentage of the eyes within ±0.25 D, ±0.50 D, and ±1.00 D of the target refraction were calculated and compared. 3. Subjective postoperative refraction of 70 patients who were diagnosed with age-related cataract and axial myopia and had been implanted intraocular lens SN60 WF were collected three months later. The long eye optimized intraocular lens constant A, SF, p ACD were calculated by using the third IOL power calculator formulas SRK/T、Holladay I、 Hoffer Q combine with axial length, keratometry, anterior depth measured by Lenstar900 and IOL power implanted. These long eye optimized IOL constants were then used to calculate the theoretical prediction of postoperative refractive outcomes that would have been achieved if they had been used in all cases. Associated mean absolute errors(MAE) and mean error(ME) in deviation from the predicted postoperative refraction as well as the percentage of the eyes within ±0.25 D, ±0.50 D, and ±1.00 D of the target refraction were calculated and compared. 4. Statistical analysis of absolute errors required a cubic root transformation to convert data to normal distributions for statistical analysis. A one-way analysis of variance(ANOVA) test was used. All statistical analyses were performed using SPSS software 16.0, a P value less than 0.05 was considered significant.Results:1. The absolute predicted refractive error for the SRK/T、Holladay I、 Hoffer Q IOL formulas used in combination or separately became a little smaller when using the optimized IOL constants, and the percentage of eyes within ±0.25 D, ±0.50 D increased slightly. A one-way analysis of variance(ANOVA) test found the predicted refractive error for the SRK/T、Holladay I、 Hoffer Q IOL formulas used in combination or separately when using the actually used IOL constant and the optimized IOL constants have no statistically significant differences(P>0.05). 2. The predicted ME, MAE have no significant change between the using of optimized IOL constant and personalized constant. On the distribution of predicted error, the percentage of eyes within ±0.25 D, ±0.50 D increased slightly using the personalized constant. The difference between the MAE using optimized IOL constant and personalized constant in each group have no statistically significant. There is no statistically significant difference in the MAE between 3 formulas in group 1, 2. 3. The MAE decreased approximately 0.2D and the predicted error within ±0.25 D, ±0.50 D increased slightly. The difference between the MAE using long eye optimized IOL constant compare to the optimized constant in each group have statistically significant(P=0.025,0.046,0.036<0.05).The long eye optimized IOL constant also decrease the ratio of hyperopia predicted error of SRK/T、Holladay I、 Hoffer Q.Conclusion:1. IOL constant optimization is beneficial to the postoperative refractive result of cataract surgery. As for the same axial length, keratometry measurement and apparatus settings, one can referent to the optimized constant on ULIB web when lacking of constant optimization. 2. The personalized constant can achieve the similar postoperative refractive result with the optimized constant, and the difference between them have no clinical significantce. The IOL constant optimization is much easy when collecting cases. We recommend the constant optimization prior to personalization when comes to the clinical application. 3. The long eye optimized constant achieved a more precise postoperative refractive prediction and decreased the ratio of hyperoptic error. The optimized constant may can’t calibrate the deviation of axial length measurement and ELP prediction from normal eye, the long eye IOL constant adjustment or optimization is beneficial to achieve better postoperative refractive result.