In myopic eye with a larger capsular bag, the use of the same IOL size could lead to an insufficient capsular tension, resulting in Abstract Aim: To study the performance of the implanted both one-piece and three-piece IOLs in relation to the enlarged diameters of the capsular bags of the highly myopic eyes. Subjects and Methods: Patient were randomly divided into two groups; group (A), included 25 eyes that underwent phacoemulsification with implantation of one-piece IOLs, Group (B) included 25 eyes that underwent phacoemulsification with implantation of three-piece IOLs. All patients include in this study were high myopes with axial length greater than 26.5 mm. All eyes were planned for clear lens extraction or cataract extraction. Results: In group (A), a statistically significant negative correlation was found between the diameters of the capsular bags and the diameters of the implanted on -piece IOLs. The correlation coefficient (r) is -0.56. In group (B), a statistically significant positive correlation was found between the diameters of the capsular bags and the diameters of the implanted three-piece IOLs. The correlation coefficient (r) is 0.88. Conclusion:The study of this correlation is to help in answering an important question, that is, does one diameter IOL fit every capsular bag? The statistical analyses in both groups point to statistically significant correlation between the diameters of the capsular bags and the diameters of the implanted IOLs i.e. focuses to the divergence between the size of the IOLs and that of the capsular bag.