Okihiro Nishi

Preventing posterior capsule opacification by creating a discontinuous sharp bend in the capsule

PURPOSE To clarify which factor--intraocular lens (IOL) design or material--contributes most to the inhibition of migrating lens epithelial cells (LECs). SETTING Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. METHODS After phacoemulsification, an acrylic IOL with sharp optic edges was implanted in 1 eye and a poly(methyl methacrylate) (PMMA) IOL with an optic design similar to that of the acrylic IOL in the contralateral eye of 4 rabbits. RESULTS The Miyake view and histopathological findings 3 weeks after surgery revealed that the lens capsule wrapped tightly around the optic edges, conforming to a distinctly sharp rectangular bend there with both IOL types in all rabbits. The migrating-LECs were inhibited at the site, and a massive Soemmerings ring cataract was formed. CONCLUSIONS The discontinuous sharp capsule bend created by the sharp optic edges in both IOL types appeared to induce contact inhibition of the migrating LECs. The preventive effect of an acrylic IOL on posterior capsule opacification may be design dependent.

Inhibition of Migrating Lens Epithelial Cells at the Capsular Bend Created by the Rectangular Optic Edge of a Posterior Chamber Intraocular Lens

BACKGROUND AND OBJECTIVE To study the mechanism of the reportedly low incidence of posterior capsule opacification (PCO) in eyes treated with a posterior chamber intraocular lens (PC IOL). MATERIALS AND METHODS Various IOL designs, including the PC IOL, were studied using scanning electron microscopy. Rabbit lens capsules were studied histopathologically 2, 3, and 4 weeks after implantation of a PC IOL in one eye and a biconvex polymethylmethacrylate (PMMA) IOL in the contralateral eye as a control. RESULTS The optic edge of the PC IOL was sharp and rectangular, whereas that of the biconvex PMMA or silicone IOLs from various manufacturers had been smoothed and rounded by polishing. PCO was significantly reduced in the eye with a PC IOL in all rabbits. The lens capsule wrapped tightly around the optic edge of the PC IOL so that it conformed to the same shape and thereby created a distinct rectangular bend in the capsule or a rectangle between the optic edge and the posterior capsule. Migrating lens epithelial cells (LECs) were obviously inhibited at that site. CONCLUSIONS A discontinuous capsular bend or rectangle created by the sharp, square optic edge of the PC IOL may have induced contact inhibition to migrating LECs and reduced PCO. How, whether, and to what extent this design-dependent effect is influenced by features of the IOL material needs to be clarified by comparison with results achieved with an IOL made from the same material in a different design and vice versa.

Posterior capsule opacificationPart 1: Experimental investigations

Posterior capsule opacification (PCO) is the most frequent complication associated with decreased vision after cataract surgery. Previous methods of preventing PCO have not proven to be practical, effective, and safe for routine clinical procedure, but some novel concepts and methods have recently been developed. This 2-part review looks at clinical and experimental investigations of PCO, focusing on developments since 1992. Clinical aspects will be presented in a later issue. This paper addresses (1) in vitro models for PCO research; (2) pathophysiology and molecular biology of lens epithelial cells (LECs); (3) prevention of PCO. Of special interest are methods of culturing human LECs obtained by capsulotomy during cataract surgery, including those obtained with an intact capsular bag, to provide an in vitro model for investigating the pathophysiology of LECs; the effect of a sharp bend in the lens capsule that induces contact inhibition of migrating LECs; more specific inhibition of migrating LECs using an immunotoxin, b-FGF-saporin, or EDTA and RGD-peptides.

Incidence of posterior capsule opacification in eyes with and without posterior chamber intraocular lenses

ABSTRACT The incidence of posterior capsule opacification after extracapsular cataract extraction was significantly lower in eyes implanted with posterior chamber intraocular lenses than in nonimplanted eyes. The number of loops fixated in the bag was significantly smaller in the eyes that became opacified than in those that did not. These findings suggest that the posterior chamber lens suppresses the two processes that lead to opacification: the development of a ring‐shaped opacity at the site of contact between the anterior capsule rim and the posterior capsule and the migration of lens epithelial cells toward the center of the capsule. These suppressive effects were greater when the posterior chamber lens was fixated in the bag.

Effect of round-edged acrylic intraocular lenses on preventing posterior capsule opacification

Purpose: To clarify the extent to which the adhesiveness of an acrylic material influences the formation of posterior capsule opacification (PCO). Setting: Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. Methods: Two types of AcrySof® intraocular lenses (IOLs) were prepared: round edged and tumbled. The AcrySof with round edges was implanted in 1 eye in a group of 4 rabbits and the tumbled IOL, in 1 eye in a group of 5 rabbits. In both groups, the contralateral eye received a conventional AcrySof with sharp optic edges. A histopathological examination was performed 3 weeks after surgery. Results: With the round‐edged AcrySof IOL, no capsular bend formed at the optic edge and abundant lens epithelial cells (LECs) migrated posteriorly. With the sharp‐edged AcrySof lens, a sharp capsular bend formed and LEC migration was significantly inhibited. In eyes with a tumbled IOL, a capsular bend was created, but it was less marked than that created by the sharp‐edged lens and there was slightly more LEC migration posteriorly. Conclusions: The AcrySof IOL lost its preventive effect on PCO when the optic was rounded. The effect of the AcrySof lens in preventing PCO is mainly a result of its rectangular, sharp‐edged optic design. The acrylic material may play a complementary role by helping create a sharp capsular bend. Capsular bend formation is the key to the PCO preventive effect of an IOL.

Intraocular lens encapsulation by shrinkage of the capsulorhexis opening.

ABSTRACT A 57‐year‐old man with retinitis pigmentosa and subcapsular cataract had phacoemulsification with a continuous curvilinear capsulorhexis and implantation of a poly(methyl methacrylate) intraocular lens. Six months later, the patient presented with blurred vision and severe anterior capsule fibrosis which led to complete posterior chamber lens encapsulation.

The Inhibition of Lens Epithelial Cell Migration by a Discontinuous Capsular Bend Created by a Band-Shaped Circular Loop or a Capsule-Bending Ring

BACKGROUND AND OBJECTIVE This study investigated the inhibitory effect of a discontinuous capsular bend created by an intraocular lens (IOL) with a band-shaped loop or a capsule tension ring on migrating lens epithelial cells (LECs). MATERIALS AND METHODS To create a sharp bend in the capsule, the round form (shown on cross section) of the open-circular loop of a polymethylmethacrylate IOL was changed to a band-like shape, 1.0 mm wide and 0.2 mm thick. A capsule tension ring of the same shape (on cross section) with a 14-mm diameter was also made. After cataract surgery, this IOL or ring was implanted into the capsular bag in 5 rabbit eyes. The same IOL with an unmodified haptic or conventional capsule tension ring was implanted in the contralateral eye as a control. After 8 weeks, Miyake view and histopathologic examinations were performed. RESULTS LECs accumulated at the equatorial corner outside the haptic or ring, showing the inhibition of LEC migration. In the control eyes, LECs accumulated inside the haptic or ring, forming a Soemmerings ring cataract, thus showing markedly less inhibition of LEC migration on macroscopic and microscopic observations. CONCLUSIONS A discontinuous bend in the capsule significantly inhibited LEC migration in rabbit eyes. The creation of a capsular bend through the appropriate design of the IOL-haptic or capsule tension ring might significantly decrease the incidence of posterior capsule opacification for humans.

Effect of intraocular lenses on preventing posterior capsule opacification: Design versus material

Purpose: To compare the preventive effect of 4 types of design‐ and material‐matched intraocular lenses (IOLs) on posterior capsule opacification (PCO). Setting: Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. Methods: After phacoemulsification, 1 of 2 matched IOLs in 3 groups was implanted in 1 eye and the other IOL in the contralateral eye of 4 to 6 rabbits. Three weeks postoperatively, posterior view and histopathological evaluations were performed and the capsular bending effect and amount of PCO evaluated. Results: The capsular bending effect was similar between a sharp‐edged acrylic IOL (Sensar® 40e, AMO) and a sharp‐edged silicone IOL (ClariFlex®, AMO) and between the Sensar 40e IOL and a sharp‐edged acrylic IOL (AcrySof®, Alcon Laboratories). There was no significant difference between IOL types in the amount of PCO. The capsular bend effect was slightly better and the PCO amount slightly less with the ClariFlex IOL than with the round‐edged silicone PhacoFlex® II IOL (AMO). Conclusions: There was no substantial difference in PCO prevention between IOLs with sharp posterior optic edges, regardless of the IOLs material composition. The anterior edge design appeared to have no preventive effect. These results confirm that a sharp posterior optic edge is the main factor in preventing PCO.

Speed of capsular bend formation at the optic edge of acrylic, silicone, and poly(methyl methacrylate) lenses

Purpose: To evaluate how and how fast a capsular bend is created clinically at the optic edge of an intraocular lens (IOL) after cataract surgery. Setting: Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. Methods: Capsular bend formation was observed by slitlamp after maximum pupil dilation in 45 eyes of 45 patients with senile cataract. Fifteen eyes each received an AcrySof® MA60BM acrylic (Alcon), PhacoFlex II® SI‐40NB silicone (Allergan), or UV26T poly(methyl methacrylate) (PMMA) (Menicon) IOL. Patients were evaluated prospectively at 1 day and 1, 2, and 4 weeks and retrospectively (15 eyes per IOL) 1 year after cataract surgery. A capsular bend index was developed to document and categorize the capsular bend formation process at the IOL optic edge. Results: The anterior and posterior capsules adhered, with the latter attracted to the former. The adhesion always progressed from the periphery to the optic edge so that the posterior capsule eventually wrapped around the posterior optic edge, although not fully circumferentially in all cases. The process took place in 4 stages. Capsular bend formation was complete 1 month after surgery with the foldable IOLs (AcrySof, PhacoFlex II) but was significantly delayed with the PMMA IOL. After 1 year, the capsular wrapping was firm and fully circumferential at the optic edge with all IOL types in all cases. Conclusions: Capsular bend formation progressed in the same fashion but at significantly different speeds among the IOLs, suggesting that the process depends on IOL material and design. Fast, early capsular bend formation may be 1 reason AcrySof and PhacoFlex II IOLs prevent PCO statistically better than PMMA IOLs. The results indicate that PCO is prevented by the sharp capsular bend created by sharp optic edges and by quick bend formation.

Intercapsular cataract surgery with lens epithelial cell removal

ABSTRACT Characteristic lens epithelial cell behavior in the pseudophakic eye was examined by comparing 30 eyes that had extracapsular cataract surgery by the intercapsular technique and posterior chamber intraocular lens (IOL) implantation with lens epithelial cell removal but without anterior capsule capsulectomy and nine aphakic eyes that had the same procedure but without posterior chamber lens implantation over a mean follow‐up period of 30 and 23 months, respectively. Fibrous anterior capsule opacification was observed in 83% of the pseudophakic eyes in the area of contact with the IOL, while the region beyond the margin of the IOL remained transparent. Fibrous anterior capsular opacification was not noted in the aphakic eyes. This suggests that the IOL material, poly(methyl methacrylate), stimulates lens epithelial cells to undergo fibrous metaplasia and to produce collagen fibers. Various cytokines such as IL‐1 and TGF‐&bgr; synthesized by lens epithelial cells may play a crucial role as mediators in the process. We recommend that this effect be considered as a parameter of biocompatibility in developing and evaluating new biomaterials.