Capsular Bend Research Articles

Effect of the optic size of a single-piece acrylic intraocular lens on posterior capsule opacification

Purpose To investigate the effect of the optic size of an intraocular lens (IOL) with sharp optic edges on posterior capsule opacification (PCO). Setting Nishi Eye Hospital, Osaka, Japan. Methods In 5 rabbits, a single-piece 5.5 mm optic AcrySof® IOL (Alcon Laboratories) was implanted in 1 eye and a specially fabricated single-piece 7.0 mm optic AcrySof IOL was implanted in the contralateral eye. Histopathological examinations were performed 3 weeks after surgery. Results On posterior views, less PCO was noted with the 5.5 mm optic in all rabbits except 1. Histopathological sections demonstrated adhesion of the anterior and posterior capsules between the haptic and optic and the formation of a sharp capsular bend at the posterior optic edge in 3 eyes with the 5.5 mm optic but in no eye with the 7.0 mm optic. Abundant PCO was noted when a sharp capsular bend had not formed. Conclusions Capsular adhesion is a prerequisite of capsular-bend formation. The sharp optic edge alone does not provide a substantial barrier when a capsular bend is not formed. Bulky haptics such as those of the single-piece AcrySof and large optics may hamper capsular adhesion and bend formation.

Preventive effect of a second-generation silicone intraocular lens on posterior capsule opacification

Purpose: To compare the preventive effect of a second-generation silicone intraocular lens (IOL) on posterior capsule opacification (PCO) with that of a soft acrylic IOL. Setting: Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. Methods: After phacoemulsification, a silicone IOL (PhacoFlex II®) was implanted in 1 eye and an acrylic IOL (AcrySof®) in the contralateral eye of 5 rabbits. Results: The posterior view 3 weeks after surgery showed slightly more PCO in 3 eyes with the PhacoFlex II lens than in eyes with the AcrySof IOL, with the PCO obscuring the iris structures. In 2 eyes with an AcrySof IOL, slightly more PCO was seen. Histopathological examination revealed that a bend and complex folds in the posterior capsule were formed with both the PhacoFlex II and AcrySof IOLs. However, the capsular bend formed by the PhacoFlex II lens, which was caused by its blunt edge, was not as sharp as that with the AcrySof IOL and more PCO was seen in all eyes with a PhacoFlex II lens. Conclusions: Capsular bend formation does not necessarily require a sharp optic edge. A truncated optic rim of a certain thickness appears to form a bend. The capsule-bending does not appear to be an all-or-nothing effect. There seems to be a transition. That a capsular bend forms despite a blunt rather than a sharp optic edge may explain why the second-generation PhacoFlex II IOL prevents PCO better than first-generation and PMMA IOLs.

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.

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.

Preventing lens epithelial cell migration using intraocular lenses with sharp rectangular edges

Purpose To compare the preventive effect on posterior capsule opacification (PCO) of an acrylic intraocular lens (IOL) and a silicone IOL, both with sharp rectangular optic edges. Setting Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. Methods After phacoemulsification, an acrylic IOL (AcrySof®) was implanted in 1 eye and a silicone IOL (CeeOn 911) in the contralateral eye of 7 rabbits, one of which was omitted from evaluation. Results The Miyake–Apple view and histopathological findings 3 weeks after surgery revealed that the lens capsule wrapped tightly around the optic edges, conforming to a distinctly sharp bend, with both IOL types in 5 rabbits. Migrating lens epithelial cells (LECs) were inhibited at the site. The AcrySof IOL had a better capsular bend effect in the histological sections, but there was no apparent difference in PCO development between the 2 IOLs. Conclusions The CeeOn 911 silicone IOL, with sharp rectangular optic edges, showed an effect on preventing PCO that was similar to that of the AcrySof IOL. When a discontinuous capsular bend is created by an IOL with sharp optic edges, the bend may induce contact inhibition of migrating LECs regardless of the lens’ material composition.

Capsule-Bending Ring for the Prevention of Capsular Opacification: A Preliminary Report

To report the preliminary results of a study on the preventive effect of the capsule-bending ring on anterior and posterior capsule opacification (ACO and PCO, respectively). The ring is an open, band-shaped, circular polymethylmethacrylate (PMMA) ring measuring 11 mm in diameter with pre-tension (13 mm in diameter when the ring is open), 0.2 mm in thickness, and 0.7 mm in width. To retain sharp edges, the ring is not polished. The sharp edges should create a sharp, discontinuous capsular bend in the fornix, which induces contact inhibition of migrating lens epithelial cells after cataract surgery. This capsule-bending ring is inserted into the capsular fornix following phacoemulsification, prior to the implantation of an intraocular lens (IOL). In a multicenter trial, 100 patients were scheduled to undergo phacoemulsification and IOL implantation in both eyes within 1 month. The procedure was performed with the ring in 1 eye and without the ring in the other eye of each patient. The anterior capsule was prevented from coming into contact with the IOL, and ACO was significantly reduced in the eyes with the ring, rendering the capsular opening larger 3 months after surgery. PCO was obviously reduced on slit-lamp examination in the follow-up period up to 6 months, but needs to be evaluated during a longer period. This band-shaped, sharp-edged capsule-bending ring may be useful for cases that need good fundus visualization for photocoagulation or expected vitreoretinal surgery and for the prevention of PCO.

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

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). 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. 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. 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.

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

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). 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. 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 Soemmering's ring cataract, thus showing markedly less inhibition of LEC migration on macroscopic and microscopic observations. 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.