Early experience with STAAR silicone elastic lens implants

Dislocation of a plate-haptic silicone intraocular lens into the anterior chamber

Posterior dislocation is a well-described complication of plate-haptic intraocular lenses (IOLs). It usually occurs after an opening in the posterior capsule, either intraoperatively or after a neodymium: YAG capsulotomy occurs. We report a case of anterior luxation of a plate-haptic silicone IOL occurring 4 months after uneventful cataract surgery. This case emphasizes the need for a small and continuous capsulorhexis as well as in-the-bag implantation of plate-haptic IOLs.

Position of poly(methyl methacrylate) and silicone intraocular lenses after phacoemulsification

PURPOSE

To compare the positional change of poly(methyl methacrylate) (PMMA) and silicone intraocular lenses (IOLs) in vivo after phacoemulsification.

SETTING

Taipei Municipal Yang-Ming Hospital, Taipei, Taiwan.

METHODS

A prospective study of 70 cataractous eyes treated by phacoemulsification with IOL implantation was carried out. The eyes were randomized into 2 groups based on IOL type: 1-piece PMMA IOL; 3-piece silicone IOL. The amount of IOL tilt and decentration was measured and anterior chamber depth (ACD) determined by Scheimpflug photography using an anterior eye segment analysis system (EAS-1000, Nidek). All eyes were examined 1 week and 1 to 6 months after surgery.

RESULTS

No statistically significantly differences were found in the amount of tilt and decentration between 2 IOL types throughout the study. The ACDs were relatively constant in both groups through the early postoperative periods.

CONCLUSION

The stability of PMMA and silicone IOLs were the same after phacoemulsification.

Fixation elements on plate intraocular lens: large positioning holes to improve security of capsular fixation

OBJECTIVE

This study aimed to evaluate in rabbit eyes the effects of large positioning holes in one-piece silicone plate-haptic intraocular lenses (IOLs) with respect to security of capsular bag fixation. Mechanical strength of capsular fixation is correlated with the histologic findings of regenerating lens material and fibrous tissue ingrowth through the positioning holes on silicone plate IOLs, comparing capsules implanted with large-hole style plate IOLs to fellow capsules implanted with small-hole style plate IOLs.

DESIGN

The study design was a prospective, randomized, experimental study.

PARTICIPANTS

A total of 40 fellow capsular bags from 20 New Zealand white rabbits were examined. Capsules implanted with conventional small-hole silicone plate IOLs were used as the control in all pairs of fellow capsules.

INTERVENTION

Phacoemulsification and implantation of a silicone plate IOL with small positioning holes in one eye and implantation of a silicone plate IOL with large positioning holes in the fellow eye were measured. All rabbits were killed at 2 months. The force required to extract the IOLs from the capsular bag was measured. All capsular bags underwent histopathologic analysis.

MAIN OUTCOME MEASURES

Extraction force measurements and histopathologic examination, comparing capsules implanted with small-hole plate IOLs with fellow capsules implanted with large-hole plate IOLs, were measured.

RESULTS

The large-hole style IOL required significantly more force to extract from the capsular bag compared to the conventional small-hole style (P = 0.003). Histologically, proliferating lens epithelial material and fibrous tissue were observed growing through all of the large positioning holes (synechia formation) but not through any of the small positioning holes.

CONCLUSIONS

Silicone plate IOLs with large positioning holes become affixed more firmly within the capsular bag compared to conventional small-hole plate IOLs. These findings suggest that large holes in silicone plate IOLs allow for superior capsular bag fixation. This should reduce the rates of decentration and dislocation.

Effect of 3.0 mm tunnel and 6.0 mm corneoscleral incisions on the blood-aqueous barrier

PURPOSE

To study of the effect of silicone intraocular lens (IOL) implantation using a 3.0 mm tunnel incision with that of implantation though a 6.0 mm corneoscleral incision after phacoemulsification in human eyes.

SETTING

Department of Ophthalmology, University of Köln, Germany.

METHODS

In a prospective, randomized clinical study, 50 patients with senile cataract had phacoemulsification and IOL implantation through a 3.0 mm tunnel or a 6.0 mm corneoscleral incision. To assess blood-aqueous barrier (BAB) disruption, preoperative and postoperative sodium fluorescein concentrations in the anterior chamber were measured with the Fluorotron Master II. Diclofenac sodium 0.1% was applied to the operative eyes five times a day for 5 days. The contralateral eyes served as controls.

RESULTS

There was no significant between-group difference in sodium fluorescein concentrations in the 5 days after surgery.

CONCLUSION

The findings underline our clinical impression that BAB disruption 5 days after surgery does not differ significantly with the type and length of scleral incision used for IOL implantation.

Pathology of silicone intraocular lenses in human eyes obtained postmortem

The increased use of phacoemulsification and small incision surgery has led to interest in a soft intraocular lens (IOL) for implantation after cataract extraction. We present the pathologic findings of seven eyes obtained postmortem from five patients with silicone IOLs. Length of implantation ranged from 6 weeks to 13 months. There was symmetric bag-bag fixation in all cases. Two IOLs had distorted and compressed polypropylene loops, resulting in decentration. The silicone IOL appeared to be well tolerated in all cases.

Dystrophic calcification of silicone scleral buckling implant materials

In six patients, removal of solid silicone scleral buckling implant materials that had been in place between eight and 21 years disclosed gray-white deposits firmly adherent to the silicone. Four of the six patients had culture-proven infections, whereas two had no evidence of infection and had negative cultures. One of these two patients, however, had intermittent pain, which was the indication for removal of the implant. Analysis of the deposits disclosed that they were calcium phosphate. The exact mechanism responsible for the calcification on the silicone material is unknown. Dystrophic calcification can occur without infection in injured tissue wherein extracellular deposits of devitalized cells, blood cells, and lipids may act as a nidus for calcification. In the presence of infection, bacteria may serve as such a nidus. Additionally, it is possible that biofilm produced by the bacteria had a role in the deposition of calcium phosphate, as well as in its firm adhesion to the silicone materials. We considered the possibility of similar deposits developing on intraocular silicone lenses.

Assessment of the blood-aqueous barrier by fluorophotometry following poly(methyl methacrylate), silicone, and hydrogel lens implantation in rabbit eyes

Intraocular lenses of silicone, hydrogel, or acrylic materials that can be implanted through small incisions are being proposed as an alternative to conventional poly(methyl methacrylate) lenses. The potential of each of these materials to stimulate intraocular inflammation is important in their selection as an implantable material. To investigate the potential of each material, we assessed by clinical slitlamp examination, fluorophotometry, and histopathology the inflammatory response induced in the rabbit eye following phacoemulsification and implantation of hydrogel, silicone, or poly(methyl methacrylate) intraocular lenses. All lenses seemed to be equally well tolerated. In general, the degree of inflammation seen clinically decreased over the four-month study; however, anterior segment fluorophotometry showed continued mild interruption of the blood-aqueous barrier in all lens groups. Fluorophotometry is a sensitive method to assess persistent subclinical anterior segment inflammation.

Forces on intraocular lens haptics induced by capsular fibrosis. An experimental study

Electronic dynamometry measurements, performed upon intraocular lens (IOL) haptics of prototype one-piece three-loop silicone lenses, accurately defined the relationships between elastic force and haptic displacement. Lens implantations in the capsular bag of dogs (loop span equal to capsular bag diameter, loops underformed immediately after the operation) were evaluated macrophotographically 5-8 months postoperatively. The highly constant elastic property of silicon rubber permitted quantitative correlation of subsequent in vivo haptic displacement with the resultant force vectors responsible for tissue contraction. The lens optics were well centered in 17 (85%) and slightly offcenter in 3 (15%) of 20 implanted eyes. Of the 60 supporting loops, 28 could be visualized sufficiently well to permit reliable haptic measurement. Of these 28, 20 (71%) were clearly displaced, ranging from 0.45 mm away from to 1.4 mm towards the lens' optic center. These extremes represented resultant vector forces of 0.20 and 1.23 mN respectively. Quantitative vector analysis permits better understanding of IOL-capsular interactions.

Physical fixation of soft intraocular lenses

Twenty silicone lenses and seven hydrogel lenses were implanted in the bag after circular capsulotomy. After surgery the haptics were firmly fixated within the bag in all cases. Inflammation was minimal in the early postoperative period. One month after surgery the average visual acuity was 20/20 or better and the average astigmatism was less than 0.5 diopter. Neodymium:YAG laser capsulotomy was not required in any case. These soft lenses seemed to be physically fixated in the bag by capsular shrinkage. We believe that this physical fixation of soft lenses is possible only when capsular integrity is maintained.

Tissue reaction after silicone and poly(methyl methacrylate) intraocular lens implantation: a light and electron microscopy study in a rabbit model

We describe the histopathologic results of extracapsular lens extraction and silicone and poly(methyl methacrylate) (PMMA) intraocular lens (IOL) implantation in 36 rabbit eyes. Phase-contrast microscopy was used to examine precipitates on IOL surfaces and posterior capsules. Semithin and ultrathin sections were taken from the central cornea, anterior uvea, capsular bag, and retina near the posterior pole. The follow-up was one to 16 weeks. Silicone IOLs did not cause significantly less precipitation than PMMA IOLs. Precipitates consisted of spindle-shaped fibroblast-like cells, various forms of inflammatory cells and multinucleated giant cells, single melanophages, and irregularly arranged birefringent collagen fibers. Corneal endothelial edema was slightly more prominent in PMMA IOL implanted eyes. Significant retinal edema in the posterior pole area was not observed with either of the two lens types. Severe precipitation in the form of large clusters of pigment cells and inflammatory reactions seemed to depend on mechanical trauma (iris capture and lens dislocation) and individual animal reactions, but not on the lens type used.

Continuous-tear capsulotomy and insertion of a silicone bag lens

Opacification of the posterior capsule and lack of intraocular lens fixation have been recurring problems and have resulted in a gradual shift from sulcus-fixated silicone lenses to bag-fixated silicone lenses. Postoperative capsular contraction, however, can cause capsular tearing in the periphery and intraocular lens decentration. A new method of combining a small circular capsulotomy, cataract removal without anterior capsular rim tearing, and meticulous bag placement of the silicone lens seems to allow centering and secure fixation of the silicone lens.

Small incisions to control astigmatism during cataract surgery

Astigmatic changes in three series of cataract surgical procedures were compared. Two series comprised eyes having phacoemulsification and implantation of a foldable silicone lens through a 3.0 mm to 4.0 mm incision or a 5.8 mm diameter polymethylmethacrylate (PMMA) lens through a 6.0 mm incision. The third series comprised eyes having a planned extracapsular cataract extraction (ECCE) procedure through a 10.0 mm incision and implantation of a PMMA posterior chamber lens. Surgically induced cylinder changes were compared by examining preoperative and postoperative dioptric cylinder power changes without regard to axis changes and by using vector analysis to compute induced cylinder for cases with axis changes. Both phacoemulsification series had similar mean induced cylinder levels, which were significantly less than mean induced cylinder in the ECCE group at both three and six months after surgery. Over 70% of the eyes in the two small incision phacoemulsification groups achieved an uncorrected visual acuity of 20/40 or better at three months, whereas only 28% of the ECCE group achieved that acuity. We concluded that the phacoemulsification procedure induced significantly less astigmatism and provided faster visual rehabilitation than the ECCE procedure. Furthermore, the use of small diameter PMMA IOLs inserted through small incisions minimized surgically induced cylinder in a way comparable to the use of foldable silicone implants, while maintaining good visual results with fewer postoperative complications.

Complications associated with STAAR silicone implants

We compared the incidence of various complications in consecutive series of cases in which 76 eyes received STAAR silicone intraocular implants and 76 eyes received small incision IOLAB G708G polymethylmethacrylate (PMMA) intraocular implants. All surgeries were performed by the same surgeon employing the same phacoemulsification technique. A higher incidence of lens subluxation, lens repositioning, corneal edema, and elevated intraocular pressure was observed in the eyes receiving STAAR silicone implants than in the eyes receiving IOLAB PMMA implants. In addition, a YAG laser posterior capsulotomy could not be performed through several STAAR silicone RMX 1 model implants. An invasive pars plana posterior capsulotomy was necessary in these eyes. We also found that the STAAR silicone RMX 3 model implants were often pitted by the YAG laser during successful posterior capsulotomies. Despite these problems, the STAAR silicone intraocular lens group achieved corrected vision similar to the PMMA lens group.

Clinicopathologic findings after in-the-bag implantation of open-loop polymethylmethacrylate and silicone lenses in the rabbit eye

Two lens models, one all silicone with J-loop haptics, the second with PMMA optics and angled polypropylene C-loop haptics, were implanted in the capsular bag of 36 rabbit eyes following extracapsular lens extraction. Technical ease of implantation, inflammatory response, lens position, and fibrin exudation as well as precipitate formation were examined. Biomicroscopy, light and phase-contrast microscopy were used. Differences in haptic vulnerability, lens position, and fibrin clot formation were found between the two lens types. Lens-specific differences in precipitate formation could not be substantiated.

Endothelial cell loss after phacoemulsification and insertion of silicone lens implants

Central corneal endothelial cell loss was compared following primary insertion of folded posterior chamber silicone intraocular lenses (IOLs) in 29 eyes and Sinskey-style polymethylmethacrylate posterior chamber IOLs in 20 eyes. Cataracts were removed by phacoemulsification and sodium hyaluronate was used in all cases. The mean follow-up time was greater than seven months. The average cell loss was 9.6% and 10.9%, respectively. There was no significant difference in cell loss or visual results in the two groups. The amount of cell loss compares favorably with other series in which cell loss was determined following cataract surgery with and without IOL implantation.

Evaluation of 50 silicone posterior chamber lens implantations

This study presents our experience with 50 silicone intraocular lens (IOL) implants (STAAR Surgical Company, model AA-4004) in the posterior chamber. In the relatively short-term mean postoperative follow-up of seven months, the following complications were observed: iris chafing - pigmentary dispersion, 15 (30%); IOL tilt and decentration, 7 (14%); pseudophakodonesis, 6 (12%); fibrinous exudate, 3 (6%); luxation of one haptic in the anterior chamber, 1 (2%); IOL tears, 5 (10%). Visual acuity of 20/20 to 20/40 was obtained in 40 patients (80%). Although no severe consequences were noted, the long-term effects of the complications are unpredictable at present.

Soft intraocular lenses

An in-depth review of the current status of soft intraocular lenses (IOLs) is presented. We have outlined the historical aspects of IOL development from polymethylmethacrylate material to newer soft polymers such as silicones and hydrogels. Chemical, physical, and biomaterial properties as well as the advantages and disadvantages of these materials and lenses are discussed. Clinical results from international investigators are presented, along with some thoughts about future trends in small incision cataract surgery and IOL substitutes.

Photophaco fragmentation

This paper present 300 cases of photophaco fragmentation or laser-assisted cataract surgery performed before beginning an FDA study. The photophaco fragmentation procedure is designed to use the YAG laser to soften the cataractous nucleus prior to phacoemulsification surgery. Photophaco fragmentation allows easier phacoemulsification as well as phacoemulsification of lenses that would otherwise not be amenable to this procedure. The paper describes technique, results, and complications.

Comparison of induced astigmatism with phacoemulsification and extracapsular cataract extraction

This paper presents an evaluation of the astigmatism induced in two groups of consecutive surgeries for cataract. At risk is the hypothesis that phacoemulsification (Group 2) induces less astigmatism than extracapsular cataract extraction (Group 1) in a series.

Pathologic findings of an explanted silicone intraocular lens

We present a clinicopathological analysis of an explanted STAAR model B silicone intraocular lens (IOL) that was sent to the Center for Intraocular Lens Research for evaluation. Extracapsular cataract extraction (ECCE), using phacoemulsification and insertion of the silicone IOL, had been accomplished through a 3-mm scleral tunnel incision. The IOL was folded and inserted into the ciliary sulcus. Complications, including blurred vision, movement of the IOL within the eye, and glaucoma, eventually led to IOL exchange at three months post-ECCE. After removal of the silicone IOL, a modified J-loop IOL was placed in the intact capsular bag, with subsequent resolution of the increased intraocular pressure and a 20/20 + 3 visual acuity. Pathologic examination of the explanted silicone lens revealed grooves indented into the optic, extensive molding flash, and opalescence of the optic.