Posterior capsule opacification (PCO) is a major cause of long-term visual acuity loss after cataract surgery, and the factors affecting PCO are numerous and complex. Clinical data have demonstrated that an intraocular lens (IOL) not only corrects visual acuity, but also results in a lower incidence of postoperative PCO compared to extracapsular cataract extraction [1], suggesting that there is a relationship between IOL and PCO. Studies by many scholars have shown that many factors of IOL have a large impact on the occurrence of PCO. This paper presents a review of the effect of IOL factors on posterior capsular clouding. 1. IOL materials and PCO Many researchers have analyzed the posterior capsule clouding in patients after IOL implantation, showing that the percentage of posterior capsule clouding was significantly reduced in those with soft acrylic (Acrysof) IOL implants compared to those with polymethylmethacrylate (PMMA) and silicone gel (Silicone) [2], while there was no statistically significant difference between PMMA and Silicone [3,3]. There was no statistically significant difference between PMMA and Silicone [3,4]. However, for the same acrylic IOLs, the rate of postoperative PCO affecting visual acuity was higher with hydrophilic IOLs than with hydrophobic IOLs [5].Michael [6], when comparing Silicone and hydrogel IOLs, found that the extent of the anterior continuous circular tear capsule (ACCC) opening was reduced in the Silicone group during the first 6 months after surgery The contraction of the anterior capsule opening in the Silicone group was accompanied by a subsequent enlargement of the capsule opening, while the Silicone IOL caused mainly fibrosis, whereas the Hydrogel IOL caused mainly proliferation of crystal epithelial cells (LECs) on the surface of the IOL. However, Okihiro [7] et al. found that IOL material was not important for the development of PCO when they studied the relationship between IOL type and shape of the optical part and posterior cataract. Emma et al [4] randomly implanted 90 eyes with IOLs of PMMA, Silicone and Acrysof materials, all with the same size optical portion and loops, with consecutive annular tear capsules, and reviewed them at 6 months and 1, 2 and 3 years postoperatively. The results showed that there was a significant difference in the percentage of posterior capsular clouding between the three materials of IOL after 3 years. posterior capsular clouding was less in Acrysof (10%) than in PMMA (56%) and Silicone (33.5%). It was concluded that IOL with Acrysof material significantly reduced the occurrence of posterior capsular clouding compared to IOL with PMMA and Silicon materials. Jinwei Cheng et al [8] found that the incidence of posterior capsule clouding for the four common IOL materials, in descending order, was polyacrylic acid, silicone gel, PMMA, and hydrogel by Meta-analysis of the interrelationship between different biomaterial IOLs and posterior capsule clouding. It is believed that silicone gel and polyacrylic acid IOLs have good capsular histocompatibility, strong adhesion tendency, and good optical design, which can prevent and reduce the occurrence of posterior capsular clouding. The “sandwich” theory explains, to some extent, the mechanism by which acrylic IOLs prevent posterior capsular clouding. The theory is that if the IOL is made of a bioactive material (such as acrylate), it facilitates cell adhesion and cell growth on it. The single epithelial cell then adheres to both the posterior capsule and to the IOL, which binds the two together and creates a “sandwich” model. This theoretically explains why bioactive IOLs are more effective than PMMA and silicone gel IOLs in preventing the development of posterior capsule clouding, especially when the IOL is implanted within the capsule (tear edge on the lens), preventing the formation of epithelial pearl-like vesicles and significantly reducing the incidence of central posterior capsule clouding [9]. A study by Nishi et al [10] suggested that the reason for the difference in the production of PCO after IOL with different materials may be their different rates of forming capsular sharp bends. The investigators compared the degree of sharp bending of the capsular membrane after IOL surgery for materials of acrylate, silicone gel, and PMMA, respectively, whose optical portions were all sharp-edged. The formation of capsular curvature was found to proceed in the same manner, but the rate of formation was significantly different, suggesting that the process depends on the material and design of the IOL. It is thought that faster and earlier formation of capsular curvature may be one of the reasons why Acrysof and PhacoFlex II IOLs prevented the formation of PCO more than PMMA IOLs. the rapid formation of PCO at the sharp edge of the optic section was prevented at the sharp curvature of the capsular membrane. In contrast, when the edge of the optical part of Acrysof is rounded, it has no effect in stopping PCO [11].Nishi et al [11] suggested that the main reason for the ability of Acrysof IOL to stop PCO formation is the design of its square edge, and that the acrylate material IOL can assist in creating the vesicle bend, and the formation of the vesicle bend is a IOL that can stop PCO formation is the key. In a trial of five rabbits, Nishi et al [12] and others implanted an Acrysof monolithic IOL with an optical diameter of 5.5 mm in one eye and an Acrysof monolithic IOL with an optical diameter of 7.0 mm in the opposite eye, and found that all but one of the rabbits implanted with an IOL with an optical diameter of 5.5 mm had little PCO 3 weeks after surgery. Pathological sections confirmed that the adhesion of the anterior and posterior capsules between the loop and the optic and the sharp curvature of the capsule at the posterior edge of the optic were found in three eyes with 5.5 mm optic diameter IOLs, but not in eyes with 7.0 mm optic diameter IOLs, and more PCO was observed in eyes without sharp curvature of the capsule. There is some connection. Elud et al [13] used three types of unsupported IOLs with large (13 mm long with an optical section of 6.0 mm), medium (11 mm long with an optical section of 5.0 mm), and small (10 mm long with an optical section of 4.0 mm) unsupported loops, as well as conventional C-shaped loops and IOLs with adhesive added, after implantation in the eyes and found that almost all of the small unsupported loops It is not clear how much the size of the IOL affects the occurrence of posterior capsular clouding, but if the IOL is too small, the tension of the capsular bag cannot be maintained, and the area of the posterior capsule that is not in contact with the optical part of the IOL increases. A large IOL excessively stretches the capsular bag, causing an increase in tension, which also causes folds to occur in the bag, and likewise increases the space for the proliferation of crystal epithelial cells. Therefore, the appropriate IOL size should maintain proper capsular bag tension while maximizing visual access to the posterior capsule so that epithelial cell proliferation may be maximally inhibited. The overall size of a common IOL is 12 to 14 mm, and an IOL with a length of 12.5 mm and an optical diameter of 5.5 mm is most commonly used for intracapsular implantation. 3. IOL optical portion edge and posterior capsule clouding Hayashi et al [14] made a comparative study between IOLs with sharp optical portion edge and IOLs with rounded edge, and found that the group with sharp edge kept more transparent posterior capsule one year after surgery than the group with rounded edge. , there was no essential difference in preventing PCO between IOLs with a sharp posterior edge of the optical portion. And it was found that the design of the leading edge of the optical part had no effect in preventing the occurrence of PCO, and these results affirm that the sharp trailing edge of the optical part is the main factor in preventing the formation of PCO. This is in agreement with the findings of most scholars [ 7, 15, 16]. Nishi [16] found that the sharp edge of the posterior part of the optic section correspondingly forms a vesicle sharp bend where the migration of crystal cells is inhibited, and the sharper its edge, the more pronounced the sharp bend of the vesicle and the more effective it is in preventing the production of PCO, regardless of the material.The study by Nishi et al [12] suggested that if the sharp edge of the IOL did not contribute to the vesicle sharp bend, the separate IOL at the edge of the pointed optical part is not going to produce a solid barrier. The observation of Zhang Zhenping et al [17] found that no PCO occurred in the right-angled edge group of IOL when the annular tear sac opening was moderately sized; 24.4% of the curved edge group showed PCO, and the difference was statistically significant