Centration and fixation of silicone intraocular lenses: clinicopathological findings in human autopsy eyes

Evaluation of 3 modern single-piece foldable intraocular lenses: clinicopathological study of posterior capsule opacification in a rabbit model

PURPOSE

To assess the development of posterior capsule opacification (PCO) with 3 modern single-piece foldable intraocular lenses (IOLs) in a histopathological study and to compare the potential preventive effects of the IOL design and biomaterial in retarding PCO.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Thirty-one rabbit eyes were randomly operated on with phacoemulsification and implantation of 3 single-piece foldable lenses: a hydrophilic acrylic design, the Rayner Centerflex 570H (n = 11); a hydrophobic acrylic design, the Alcon AcrySof SA30AL (n = 10); and a silicone large-hole plate design, the Staar AA-4203VF (n = 10). Central PCO (CPCO), peripheral PCO (PPCO), and Soemmering's ring formation were evaluated 3 weeks after surgery using the Miyake-Apple posterior photographic technique. Histological sections of each globe were prepared to document capsular bag status and performance of IOL geometry.

RESULTS

The acrylic IOLs (Centerflex and AcrySof) had lower CPCO and PPCO scores than the silicone plate IOL (P <.05). There was no significant difference in Soemmering's ring formation among the 3 models. Pathological evaluations revealed effective blockage of migrating lens epithelial cells (LECs) at the site of the truncated optic edge of the Centerflex and AcrySof IOLs, even in the presence of large amounts of retained/regenerative cortical material.

CONCLUSIONS

The AcrySof IOL has a hydrophobic surface and the Centerflex a hydrophilic surface, but no correlation to these characteristics could be identified. The single-piece AcrySof optic geometry created a clear-cut barrier effect equal to that of its 3-piece predecessor. The anatomic profile of the Centerflex IOL shows the same characteristics. The optics of both acrylic lenses have square truncated edges that functionally block ingrowth of migrating LECs toward the central visual axis, leaving clear posterior capsules. The square optic edge was an appropriate geometric configuration to create a barrier effect. There was no effect of the biomaterial on PCO prevention.

[History of the development of intraocular lenses]

Even though cataract surgery has been practiced for over 2000 years, modern cataract surgery started just some 50 years ago. with the first IOL implantation by Sir Harold Ridley. The development of intraocular lenses was accompanied by great successes and disasters. With the fast development of cataract surgical techniques over the past 15 years (ECCE, Phacoemulsification, Capsulorhexis) a successful marriage between IOL-developments and surgery was established. Indication profiles for cataract surgery and IOL implantation extended to more and more patient groups. At this time classical cataract surgery is further developing into refractive intraocular lens surgery to correct higher ametropia in clear lens or phakic eyes. This development was only possible because of the improvements of surgical techniques and implants in classical cataract surgery.

Effect of large positioning holes on capsule fixation of plate-haptic intraocular lenses

PURPOSE

To compare the centration and fixation of silicone plate-haptic intraocular lenses (IOLs) with different-sized positioning holes.

SETTING

Eye Clinic of the Johannes Gutenberg-University Mainz, Mainz, Germany.

METHODS

In a prospective randomized study, 51 Chiroflex C10 and 56 Chiroflex C11 IOLs were implanted under standardized conditions by the same surgeon. The IOL position was documented at the end of surgery and by retroillumination on the first day and 5 months postoperatively. The positioning-hole area was evaluated by ultrasound biomicroscopy (50 MHz) 5 months postoperatively.

RESULTS

One day postoperatively, no IOL in either group was decentered more than 1.0 mm. After 5 months, 33% of the C10 and 42% of the C11 IOLs were decentered between 0.5 and 1.0 mm, and 11% of the C10 and 8% of the C11 IOLs were decentered more than 1.0 mm (maximum 1.23 mm and 1.41 mm, respectively). Up to the first postoperative day, 20% of the C10 and 22% of the C11 lenses were rotated more than 15 degrees. At 5 months, an additional 15% of the C10 and 19% of the C11 lenses were rotated. Ultrasound biomicroscopy showed no tissue or capsule adhesion in the holes in most cases (85% C10 group; 71% C11 group). No difference was statistically significant.

CONCLUSIONS

Larger positioning holes did not prevent IOL decentration or rotation; thus, this IOL design appears unsuitable for correcting astigmatism. Because tissue in the positioning hole was rare with both lens types, it is doubtful that enlarged plate-haptic perforations will prevent IOL luxation into the vitreous cavity after capsulotomy.

Comparative evaluation of plate haptic lenses with smaller and larger positioning holes

PURPOSE

To evaluate the visual outcome, intraoperative problems and postoperative complications of plate haptic intraocular lenses with smaller foot plate positioning holes and larger holes.

METHODS

Fifty eyes of 50 patients underwent clear corneal phacoemulsification with implantation of either small hole plate haptics (25 eyes) or large hole plate haptic lenses (25 eyes). The intraoperative complications were noted and the postoperative parameters were evaluated on the first day, 1 week, 1 month, 3 months, 6 months and 12 months. These included the best corrected visual acuities, intraocular lens (IOL) decentring, diameter of anterior capsulorhexis and posterior capsule opacification.

RESULTS

The mean duration of follow-up was 14.8+/-2.1 months in the group with the small foot plate positioning holes (Chiron C10UB) lens and 15.6+/-3.2 months in the group with the large feet plate positioning holes (Chiron C11UB) lens. The was no significant difference in the visual acuities of the two groups. The mean IOL decentring was 0.42+/-0.28 mm in the C10UB lenses and 0.24+/-0.10 mm in the C11UB lenses (P = 0.05). The mean diameter of the anterior capsulorhexis was 4.68+/-0.23 mm in the former, while it was 4.21+/-0.68 mm in the latter (P = 0.0027). The posterior capsule opacification was significantly increased in the C11UB group (P = 0.0298). Neodymium : yttrium aluminium garnet (Nd: YAG) laser capsulotomy was required in 8% of the C10UB group, compared to 28% in the C11UB group.

CONCLUSION

Results are similar with the two types of plate haptic lenses. The lenses with larger holes have a significantly higher posterior capsule opacification and more anterior capsulorhexis contracture, although the IOL decentring is less with these lenses.

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part I: Elimination of fixation-induced decentration to achieve precise optical correction and visual rehabilitation

PURPOSE

Realizing that precise posterior chamber intraocular lens (PC-IOL) centration is needed to consistently achieve good optical results and visual rehabilitation after modern cataract surgery, the authors assessed the status and success rate of lens haptic fixation and its correlation with lens optic centration-decentration in a large series of eyes with PC-IOLs obtained postmortem.

DESIGN

Prospective analysis of pseudophakic eyes obtained postmortem.

PARTICIPANTS

A total of 3493 human eyes obtained postmortem, the largest database of such specimens available to date.

METHODS

Miyake-Apple posterior photographic technique.

MAIN OUTCOME MEASURES

The amount of decentration of rigid PC-IOLs and small-incision foldable PC-IOLs was analyzed, and the results were correlated with the type of fixation that had been achieved in each case.

RESULTS

Determination of mean values revealed that capsular bag fixation was achieved in 52.05% of eyes, asymmetric bag-sulcus fixation in 34.21 % of eyes, and sulcus-sulcus fixation in 13.74% of eyes. Asymmetrically fixed lenses consistently showed significant decentration. During the past 5 years (1993-98), the overall rate of in-the-bag fixation increased to 59.2%; by 1998 it had increased to 64%. Most significantly, success in achieving bag-bag fixation of foldable IOLs implanted in association with modern capsular surgery with small incisions has surged to 90% over the past 4 years.

CONCLUSIONS

The authors found a direct correlation of decentration in eyes with asymmetric fixation, and the results underscore the need for careful in-the-bag haptic placement. Although few surgeons today would dispute the goal to implanting haptics in the capsular bag, these findings show that the overall success rate over the years has, while improving, remained surprisingly low. The overall success rate of about 60% seen with all lens designs is probably as good as can be expected with classic large-incision extracapsular techniques. However, and most important and encouraging, the success rate of haptic fixation in cases with foldable lenses has improved dramatically during the past 4 years (up to the 90% range). This coincides with the present emphasis on modern capsular surgery and small-incision techniques used to insert these lenses.

Evaluation of a 3-piece silicone intraocular lens with poly(methyl methacrylate) haptics

PURPOSE

To evaluate the safety and performance of a foldable silicone intraocular lens (IOL) in small incision phacoemulsification surgery.

SETTING

Vaasa Central Hospital, Vaasa, Finland.

METHODS

Phacoemulsification with primary implantation of a posterior chamber IOL was performed in 50 patients. All eyes were implanted with a CeeOn IOL (model 920, Pharmacia & Upjohn) with a silicone optic and poly(methyl methacrylate) haptics. The ease of folding, implanting, and unfolding the IOL in the bag were recorded. Visual acuity, postoperative complications, optic decentration, and optic tilt were measured at 5 postoperative visits. The IOLs were evaluated for haze and discoloration and the IOL surface, for inflammatory or pigment deposits. Follow-up was 12 months.

RESULTS

In 44 of 50 cases, folding the IOL was easy, and in 46 of 50, unfolding the IOL was controlled. The mean follow-up was 11.45 months +/- 0.52 (SD). No postoperative complications occurred, and 96% of patients achieved a best corrected visual acuity (BCVA) of 0.5 or better and 56%, a BCVA of 1.0 or better. The IOL decentration was less than 0.25 mm in 89% of cases, and there was no optic tilt. The neodymium:YAG laser capsulotomy rate was 11%.

CONCLUSION

Good visual outcome and excellent centration were achieved with the CeeOn model 920 IOL. It is therefore suitable for small incision cataract surgery. Because of the IOL's smooth, polished surface, the choice of instruments for folding and implantation is important.

Decentration of 3-piece versus plate-haptic silicone intraocular lenses

PURPOSE

To compare the incidence of decentration with 2 types of silicone intraocular lenses (IOLs).

SETTING

John A. Moran Eye Center, University of Utah Medical Center, Salt Lake City, Utah, USA.

METHODS

Selection criteria for this retrospective study included patients who had uncomplicated cataract surgery with a clear cornea or scleral tunnel incision with a curvilinear capsulorhexis and capsular bag implantation of a silicone IOL. After a mean follow-up of 14 months (range 12 to 18 months), 54 eyes implanted with a 3-piece lens (AMO SI-30) and 58 eyes implanted with a plate-haptic lens (Staar AA403) were examined for posterior chamber IOL decentration. The decentration criterion was 0.5 mm or more from the center of the pupil. Detailed chart review of preoperative and postoperative measurements was performed for each patient.

RESULTS

Eighteen of the 3-piece IOLs (33%) and 11 of the plate-haptic IOLs (20%) were decentered 0.5 mm or more (P = .129). Using photographic analysis, the mean IOL decentration with the 3-piece IOL (1.12 mm +/- 0.198 [SD]) was significantly greater than with the plate-haptic IOL (0.632 +/- 0.278 mm)(P < .001). No statistically significant correlation was found between the centered or decentered IOL groups' preoperative refraction, axial length, capsulorhexis size, type of incision, or rate of neodymium:YAG laser capsulotomy.

CONCLUSIONS

No statistically significant difference was seen between the decentration rates of 3-piece and plate-hepatic IOLs; however, the amount of decentration with the 3-piece IOL was significantly greater than with the plate-hepatic IOL. Other factors did not contribute to IOL decentration.

Staar Collamer intraocular lens: clinical results from the phase I FDA core study

PURPOSE

To assess the early postoperative efficacy and safety of the Staar Collamer intraocular lens (IOL) in small incision cataract surgery.

SETTING

Six private ophthalmology practices geographically distributed throughout the United States.

METHODS

One hundred twenty-five patients with a mean age of 72.1 years were enrolled in the U.S. Food and Drug Administration (FDA) Phase 1 clinical study of the Staar Collamer IOL after having cataract removal by phacoemulsification. Of these, 107 completed 4 to 6 months of follow-up.

RESULTS

At 4 to 6 months postoperatively, 97.1% of patients achieved 20/40 or better corrected visual acuity; 100% of patients without pre-existing pathology (best case) achieved the same result; both results were better than FDA grid values. No persistent sight-threatening complications were reported. Through 6 months, 4.7% of patients required a neodymium:YAG capsulotomy. No IOL dislocations or removals were reported.

CONCLUSION

Results indicate that the Collamer material is safe and effective for platehaptic IOLs used in small incision cataract surgery.

Mini-haptics to improve capsular fixation of plate-haptic silicone intraocular lenses

PURPOSE

To evaluate the effects of a new mini-haptic design on the strength and stability of capsular bag fixation of plate-haptic silicone intraocular lenses (IOLs) and determine whether this design encourages the growth of regenerating lens material or fibrous tissue around the haptic biomaterial and thus improves lens fixation in the capsular bag.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Department of Ophthalmology, Charleston, South Carolina, USA.

METHODS

Six rabbits had bilateral continuous curvilinear capsulorhexis, phacoemulsification, and plate-haptic silicone IOL implantation. Each rabbit had a small-hole plate IOL (Chiron C10UB) implanted in the right eye and a mini-haptic plate IOL (Chiron C40UB) in the left eye. All rabbits were killed at 2 months. The force required to extract one haptic from the capsular bag was measured with a digital force gauge. Histopathologic analysis was performed on all specimens.

RESULTS

The mini-haptic style IOLs required significantly more extraction force than the small-hole design (P = .011). Histopathologically, proliferating lens epithelial cells were observed growing circumferentially around the mini-haptics, causing a 360 degree synechia formation. This formation did not occur with the conventional small-hole plate IOLs used as the control.

CONCLUSIONS

Lens epithelial cell proliferation around the mini-haptics significantly improved capsular bag fixation of the plate-haptic silicone IOL. This should decrease the incidence of clinical decentration and dislocation.

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.

Security of capsular fixation: small-versus large-hole plate-hepatic lenses

PURPOSE

To assess the effect of relatively large positioning holes on the security of capsular bag fixation of plate-haptic silicone intraocular lenses (IOLs).

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

This study tested the hypothesis that larger holes allow ingrowth of lens material, fibrous tissue, or both through them, which helps fixate the lens more firmly in the capsular bag. Five rabbits had bilateral continuous curvilinear capsulorhexis, phacoemulsification, and implantation of a plate-haptic silicone IOL. An IOL with a small, round positioning hole (Staar AA-4203V) was implanted in the right eye in each rabbit, and a large-hole IOL (Staar AA-4203VF) was implanted in the left eye. After 2 months, all rabbits were killed. The force required to extract one haptic from the capsular bag was measured with a digital force meter. All eyes had histopathological analysis.

RESULTS

It was slightly more difficult to extract a large-hole IOL from the capsular bag, although this trend was not statistically significant. However, histopathological analysis consistently showed 360 degree synechia formation through the holes, showing that the IOL could be securely fixed in position.

CONCLUSIONS

Proliferation of lens epithelial cells through a large positioning hole in a plate-haptic silicone IOL may improve the long-term security of capsular bag fixation. This will help reduce the incidence of IOL decentration and dislocation.