Posterior capsule opacification and neodymium: YAG capsulotomy with heparin-surface-modified intraocular lenses

Interventions for preventing posterior capsule opacification

BACKGROUND

Posterior capsule opacification (PCO) remains the most common long-term complication after cataract surgery. It can be treated by Nd:YAG laser capsulotomy, however this may lead to other complications and laser treatment is not available in large parts of the developing world. Therefore, many studies try to find factors influencing the development of PCO.

OBJECTIVES

To summarise the effects of different interventions to inhibit PCO. These include modifications of surgical technique and intraocular lens (IOL) design, implantation of additional devices and pharmacological interventions.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE, LILACS in March 2009 and reference lists of identified trial reports.

SELECTION CRITERIA

We included only prospective, randomised and controlled trials with a follow-up time of at least 12 months. Interventions included modifications in surgical technique explicitly to inhibit PCO, modifications in IOL design (material and geometry), implantation of additional devices and pharmacological therapy compared to each other, placebo or standard treatment.

DATA COLLECTION AND ANALYSIS

We extracted data and entered it into RevMan. We compared visual acuity data, PCO scores and YAG capsulotomy rates and performed a meta-analysis when possible.

MAIN RESULTS

Sixty six studies were included in the review. The review was divided into three parts. 1. Influence of IOL optic material on the development of PCO. There was no significant difference in PCO development between the different IOL materials (PMMA, hydrogel, hydrophobic acrylic, silicone) although hydrogel IOLs tend to have higher PCO scores and silicone IOLs lower PCO scores than the other materials. 2. Influence of IOL optic design on the development of PCO. There was a significantly lower PCO score (-8.65 (-10.72 to -6.59), scale 0 to 100) and YAG rate (0.19 (0.11 to 0.35)) in sharp edged than in round edged IOLs, however not between 1-piece and 3-piece IOLs. 3. Influence of surgical technique and drugs on the development of PCO. There was no significant difference between different types of intraoperative/postoperative anti-inflammatory treatment except for treatment with an immunotoxin (MDX-A) which led to a significantly lower PCO rate.

AUTHORS' CONCLUSIONS

Due to the highly significant difference between round and sharp edged IOL optics, IOLs with sharp (posterior) optic edges should be preferred. There is no clear difference between optic materials. The choice of postoperative anti-inflammatory treatment does not seem to influence PCO development.

Effect of intraocular lens design on posterior capsule opacification

Posterior capsule opacification (PCO) remains the most common long-term complication after cataract surgery. Many studies have attempted to identify factors that influence the development of PCO. The aim of this systematic review based on Cochrane methodology was to summarize the effects of intraocular lens (IOL) geometry, including modifications of the IOL optic (especially optic edge design) and haptics, on the development of PCO. Twenty-six prospective randomized controlled trials with a follow-up of at least 12 months were included. In 5 of 7 studies, visual acuity was better in sharp-edged IOLs than in round-edged IOL. The PCO score was significantly lower with sharp-edged IOLs but did not differ significantly between 1-piece and 3-piece open-loop IOLs. Because of the significant difference in the PCO score, sharp-edged IOL optics should be preferred to round-edged IOL optics.

Influence of fibronectin on the adherence of Staphylococcus epidermidis to coated and uncoated intraocular lenses

PURPOSE

To determine the effect of the modification of intraocular lens (IOL) surface properties on the adhesion of Staphylococcus epidermidis caused by fibronectin (FN) as the predominant proadhesive glycoprotein of the eye's initial foreign body reaction.

SETTING

University of Saarland, Homburg/Saar, Germany.

METHODS

Eleven IOL types were tested. The IOLs were of poly(methyl methacrylate), acrylate, or silicone. Some were surface modified with heparin or polysaccharide coating. The IOLs, unadsorbed or preadsorbed with fibronectin (FN), were incubated with [(3)H]-thymidine-labeled S epidermidis Rp62a, and the amount of adherent microorganisms was determined.

RESULTS

Attachment of S epidermidis adhesion to various types of IOLs, both unadsorbed and FN precoated, varied significantly. The attachment to highly adhesive IOLs was almost 4-fold greater than that to low-adhesive IOLs. Attachment to FN precoated IOLs was generally enhanced compared with attachment to unadsorbed IOLs. Heparin surface modification resulted in no or a modest reduction in bacterial adhesion compared with unmodified IOLs. Bacterial adhesion was highly statistically significantly less on IOLs with polysaccharide surface modification.

CONCLUSIONS

There was significant variability in S epidermidis adhesion to IOLs as a function of design, material, surface modification, and FN preadsorption. Application of the findings may foster new developments to further reduce the major complication in cataract surgery, infective endophthalmitis.

Interventions for preventing posterior capsule opacification

BACKGROUND

Posterior capsule opacification (PCO) remains the most common long-term complication after cataract surgery. It can be treated by Nd:YAG laser capsulotomy, however, this may lead to other complications and laser treatment is not available in large parts of the developing world. Therefore, many studies try to find factors influencing the development of PCO.

OBJECTIVES

To summarise the effects of different interventions to inhibit PCO. These include modifications of surgical technique and intraocular lens (IOL) design, implantation of additional devices and pharmacological interventions.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE, LILACS in January 2007 and reference lists of identified trial reports.

SELECTION CRITERIA

We included only prospective, randomised and controlled trials with a follow-up time of at least 12 months. Interventions included modifications in surgical technique explicitly to inhibit PCO, modifications in IOL design (material and geometry), implantation of additional devices, and pharmacological therapy, compared to each other, placebo or standard treatment.

DATA COLLECTION AND ANALYSIS

Data were extracted and entered into Review Manager. Visual acuity data, PCO score and YAG capsulotomy rates were compared and a meta-analysis was performed when possible.

MAIN RESULTS

Fifty three studies were included in the review. The review was divided into three parts. (1) Influence of IOL optic material on the development of PCO. Compared to other materials, the meta-analysis of the included studies showed a significantly higher PCO score (overall effect: 12.39 (95% confidence interval: 9.82 to 14.95), scale 0 to 100) and YAG rate (odds ratio: 8.37 (3.74 to 20.36)) only in hydrogel IOLs. (2) Influence of IOL optic design on the development of PCO. There was a significantly lower PCO score (-8.65 (-10.72 to -6.59), scale 0 to 100) and YAG rate (0.19 (0.11 to 0.35)) in sharp edged than in round edged IOLs, however, not between 1-piece and 3-piece IOLs. (3) Influence of surgical technique and drugs on the development of PCO. There was no significant difference between different types of intra-/postoperative anti-inflammatory treatment except for treatment with an immunotoxin (MDX-A) leading to a significantly lower PCO rate.

AUTHORS' CONCLUSIONS

Due to the highly significant difference between round and sharp edge IOL optics, IOLs with sharp (posterior) optic edges should be preferred. There is no clear difference between optic materials, except for hydrogel IOLs, that showed more PCO than the other materials. The choice of postoperative anti-inflammatory treatment does not seem to influence PCO development.

Adverse clinical consequences of neodymium:YAG laser treatment of posterior capsule opacification

PURPOSE

To evaluate the clinical consequences of complications from neodymium:YAG (Nd:YAG) laser capsulotomy for posterior capsule opacification (PCO) over the lives of cataract patients.

SETTING

CHU de Caen, Caen, France.

METHODS

A model was constructed to estimate the lifetime clinical consequences of postoperative PCO treated by Nd:YAG laser capsulotomy. The probability of death was modeled from French mortality tables as a polynomial function of sex and age. The probability of becoming blind was modeled as a function of age from data in the literature. The incidence of Nd:YAG complications came from the literature. The rate of Nd:YAG capsulotomy over time was modeled as a survival curve using data from a cohort of 3335 patients.

RESULTS

Over 9 years in a 70-year-old population, switching from an IOL with a 20% Nd:YAG capsulotomy rate at 3 years to an IOL with a 5% rate would avoid 1 chronic intraocular pressure increase requiring medical follow-up in every 54 surgeries, 1 case of glaucoma in every 237 surgeries, 1 case of cystoid macular edema in every 265 surgeries, and 1 retinal detachment in every 265 surgeries. A 3-year clinical study would only capture one-third to one-half of long-term adverse events of Nd:YAG capsulotomy.

CONCLUSION

Reducing PCO and the associated use Nd:YAG laser capsulotomy may contribute to preserving visual acuity in patients over their lifetimes.

Systems of analysis of posterior capsule opacification

This paper demonstrates the wide variety of systems for the analysis of posterior capsular opacification (PCO). No single system has been proved to be a gold standard and it is difficult to comment on the advantages of one system over another with the limited current knowledge on the effects of PCO on vision. There are few studies that actually compare the different systems of analysis. Researchers must ensure that the systems they use for PCO analysis are objective and must give maximum consideration to ensuring potential systematic errors are reduced to a minimum. Further research is required into how the various types and locations of PCO affect vision and how well different systems of analysis perform.

Posterior capsule opacification. Part 2: Clinical findings

The incidence of posterior capsule opacification (PCO), the most common complication of modern cataract surgery with intraocular lens implantation, seems to have decreased slightly as a result of improved surgical and cortical cleanup techniques. However, the reported incidence is still significant. The diverse findings on PCO are the result in part of studies using different criteria to clinically judge and quantify the condition. In addition, the influence of intraocular and systemic factors are only now being identified. This second of a 2-part review of PCO focuses on (1) less subjective morphological and patient-dependent means to evaluate and quantify PCO; (2) the influence of ocular factors on PCO; (3) the influence of systemic factors on PCO; (4) available means and approaches to prevent or delay PCO.

Intraocular lens bioactivity tested using rabbit corneal tissue cultures

PURPOSE

To evaluate the effects of different intraocular lens (IOL) materials on epithelial cell growth to test the sandwich theory; i.e., a bioactivity-based explanation of posterior capsule opacification (PCO) after cataract surgery.

SETTING

Central Hospital, Vaasa, and Institute of Dentistry and Turku Center for Biomaterials, University of Turku, Finland.

METHODS

Rabbit corneal tissue cultures were set up on poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, silicone, acrylate, and hydrogel IOLs for 1 week. The tissue consisted of intact epithelium and half the thickness of the corneal stroma, which was placed against the IOL. The growth of the epithelium was examined by light microscopy to evaluate the attachment of the corneal explant to the IOL surface.

RESULTS

All tissue samples grew well under the culture conditions. When grown on PMMA, HSM PMMA, silicone, and hydrogel, the tissue did not attach to the IOL or the epithelium grew around the explant, suggesting that the attachment of the stroma to the IOL was poor or nonexistent. Some explants on acrylate IOLs attached directly to the IOL surface with no epithelial ingrowth between the stroma and the IOL.

CONCLUSIONS

This tissue culture method can be used to examine the behavior of corneal tissue in contact with different IOL materials. The results suggest that the acrylate IOL may have bioactive properties. This, with the lens optic's square edge, may hinder lens epithelial cell proliferation and thus prevent PCO.

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part II: Choosing the correct haptic fixation and intraocular lens design to help eradicate posterior capsule opacification

PURPOSE

Posterior capsule opacification (PCO) is one of the most common complications of cataract surgery, and there is an urgent need to reduce its incidence. Its main treatment, neodymium:YAG (Nd:YAG) laser posterior capsulotomy, may be associated with significant morbidity and is expensive. In this study, the authors ascertain the effect of posterior chamber intraocular lens (PC-IOL) fixation and various IOL designs (rigid polymethyl methacrylate [PMMA] optic and small-incision foldable designs) on the pathogenesis of PCO.

DESIGN

Prospective analysis of pseudophakic eyes obtained postmortem.

PARTICIPANTS

A total of 3493 eyes with PC-IOLs obtained postmortem and received between 1984 and 1998.

METHODS

Miyake-Apple posterior photographic technique.

MAIN OUTCOME MEASURES

Peripheral Soemmering's ring, central PCO in the visual axis, and eyes that have had Nd:YAG laser posterior capsulotomy were analyzed and scored, and these findings were correlated with the type of fixation and IOL design.

RESULTS

The degree of formation of peripheral Soemmering's ring was not influenced by IOL fixation. The acrylic design revealed relatively low Soemmering's ring scores. In contrast, central PCO and Nd:YAG laser capsulotomy scores were consistently influenced by fixation. The scores were significantly lower in eyes with in-the-bag fixation. The bag-bag fixated acrylic-PMMA design and the three modern silicone IOL designs analyzed in this study had less central PCO and lower posterior capsulotomy scores than did the PMMA IOLs.

CONCLUSIONS

The formation of peripheral PCO (the Soemmering's ring), the precursor of clinically significant, vision-threatening PCO, is not significantly influenced by the haptic fixation pattern. It is much more dependent on the quality and thoroughness of surgical cortical cleanup. Reduction of Soemmering's ring is an important goal because the retained regenerative cortical cells within this lesion are the cells of origin of PCO. The acrylic IOL design was associated with a lessor amount of peripheral Soemmering's ring as compared with all other designs. In sharp contrast to peripheral PCO, fixation of the IOL was a highly significant factor affecting the formation and quantity of central PCO-the clinically significant opacity behind the IOL optic, measured in this series either by scoring an intact retro-optical membrane or by documenting the presence of a Nd:YAG laser posterior capsulotomy orifice. The quantity of central PCO was consistently much lower in eyes with in-the-bag fixated IOLs compared with lenses with one or both haptics out of the bag. This is best explained by the fact that secure in-the-bag fixation positions the IOL optic in the best possible position to create a barrier effect. The lowest PCO rates were generally noted with the acrylic and modern silicone IOL designs.