Relationship between intraocular lens biomaterials and posterior capsule opacification

A 3D in vitro model for assessing the influence of intraocular lens: Posterior lens capsule interactions on lens epithelial cell responses

Posterior Capsule Opacification (PCO), the most frequent complication of cataract surgery, is caused by the infiltration and proliferation of lens epithelial cells (LECs) at the interface between the intraocular lens (IOL) and posterior lens capsule (PLC). According to the "no space, no cells, no PCO" theory, high affinity (or adhesion force) between the IOL and PLC would decrease the IOL: PLC interface space, hinder LEC migration, and thus reduce PCO formation. To test this hypothesis, an in vitro hemisphere-shaped simulated PLC (sPLC) was made to mimic the human IOL: PLC physical interactions and to assess their influence on LEC responses. Three commercially available IOLs with different affinities/adhesion forces toward the sPLC, including Acrylic foldable IOL, Silicone IOL, and PMMA IOL, were used in this investigation. Using the system, the physical interactions between IOLs and sPLC were quantified by measuring the adhesion force and interface space using an adhesion force apparatus and Optical Coherence Tomography, respectively. Our data shows that high adhesion force and tight binding between IOL and sPLC contribute to a small interface space (or "no space"). By introducing LECs into the in vitro system, we found that, with small interface space, among all IOLs, acrylic foldable IOLs permitted the least extent of LEC infiltration, proliferation, and differentiation (or "no cells"). Further statistical analyses using clinical data revealed that weak LEC responses are associated with low clinical PCO incidence rates (or "no PCO"). The findings support that the in vitro system could simulate IOL: PLC interplays and predict IOLs' PCO potential in support of the "no space, no cells, no PCO" hypothesis.

Role of fibronectin and IOL surface modification in IOL: Lens capsule interactions

Posterior Capsule Opacification (PCO) is one of the most common complications of cataract surgery. While studies have shown that IOL material properties and fibronectin adsorption may affect IOL-induced PCO in the clinical setting, the mechanism governing such interactions is not totally understood. Since strong adhesion forces between IOLs and posterior capsules (PCs) have been shown to impede cell infiltration and thus reduce PCO formation, this study was designed to assess whether fibronectin adsorption and IOL material properties would impact the IOL:PC adhesion force and cell infiltration using a PCO predictive in vitro model and a macromolecular dye imaging model, respectively. Our results showed that fibronectin adsorption significantly increased the adhesion forces and reduced simulated cell infiltration between acrylic foldable IOLs and the PC at physiological temperature in comparison to fibronectin-free controls. This fibronectin-mediated strong IOL: PC bond may be contributing to low PCO rates in the clinic for acrylic foldable IOLs. In addition, acrylic foldable IOLs coated with Di(ethylene glycol) (Diglyme), a hydrophilic coating known to reduce protein adsorption, was tested for its ability to alter adhesion force and cell infiltration. We observed that IOLs coated with Diglyme coating greatly reduced surface hydrophobicity and fibronectin adsorption of acrylic foldable IOLs. Furthermore, Diglyme coated IOLs showed significantly reduced adhesion force and increased simulated cell infiltration at the IOL:PC interface. The overall results support the hypothesis that IOL surface properties and their ability to adsorb fibronectin may have great impact on the IOL:PC adhesion force. A tight binding between IOLs and PC may contribute to the reduction of cell infiltration and thus the PCO incidence rate in the clinic.

Clinical safety and efficacy of a preloaded monofocal hydrophobic acrylic intraocular lens in a real-world population

BACKGROUND

This study was designed to evaluate visual, refractive and safety outcomes in eyes after they underwent phacoemulsification and implantation of a preloaded monofocal hydrophobic acrylic intraocular lens.

METHODS

This was a single center observational study conducted at Ashford and St Peter's Hospitals NHS Foundation Trust, United Kingdom. Patients were included if they had cataract extraction with in-the-bag implantation of the EyeCee® One preloaded intraocular lens from August to October 2019. Pre-operative, surgery-related and 2 weeks and 3 months post-operative data was collected. Surgeons at this trust were then asked to complete a feedback form to evaluate their experience of implanting the EyeCee® One.

RESULTS

One hundred fifty-two eyes were included in the study. Ninety-four (62%) of these eyes had cataract but no concomitant ocular pathology that could potentially affect visual acuity. Three months post-operatively, 98.7% of all eyes had monocular CDVA ≤0.3 logMAR. 100% of the eyes without concomitant ocular pathology achieved this target. The mean CDVA of all eyes in this study improved from 0.43 ± 0.43 logMAR pre-operatively, to 0.05 ± 0.11 logMAR post-operatively (p < 0.05). The mean sphere and spherical equivalent values showed significant improvements (p < 0.05) and (p < 0.05). There were no intraoperative complications and 1.3% of patients reported complications 2 weeks post-operatively. All of the participating surgeons said they would use the EyeCee® One again with 64% providing an overall rating of 'excellent' for their experience of implanting this intraocular lens.

CONCLUSIONS

This study indicates excellent post-operative visual acuity and refractive outcomes in eyes after EyeCee® One implantation. This is accompanied with very little risk of intraoperative and post-operative complications.

Application of Collagen I and IV in Bioengineering Transparent Ocular Tissues

Collagens represent a major group of structural proteins expressed in different tissues and display distinct and variable properties. Whilst collagens are non-transparent in the skin, they confer transparency in the cornea and crystalline lens of the eye. There are 28 types of collagen that all share a common triple helix structure yet differ in the composition of their α-chains leading to their different properties. The different organization of collagen fibers also contributes to the variable tissue morphology. The important ability of collagen to form different tissues has led to the exploration and application of collagen as a biomaterial. Collagen type I (Col-I) and collagen type IV (Col-IV) are the two primary collagens found in corneal and lens tissues. Both collagens provide structure and transparency, essential for a clear vision. This review explores the application of these two collagen types as novel biomaterials in bioengineering unique tissue that could be used to treat a variety of ocular diseases leading to blindness.

Effect of time and temperature-dependent changes of IOL material properties on IOL: Lens capsule interactions

Posterior Capsule Opacification (PCO) is the most common complication associated with Intraocular Lens (IOL) implantation. Based on the assumption that the interactions between an IOL and the lens capsule (LC) may influence the extent of PCO formation, a new in vitro model was developed to quantify the adhesion force of an IOL to simulated LC using a custom-designed micro-force tester. Using this system, we examined the influence of temperature (room temperature vs. body temperature) and incubation time (0 vs. 24 h) on the adhesion force between IOLs and LCs. The results show that, in line with clinical observations of PCO incidence, the adhesion force increased at body temperature and with increase in incubation time in the following order, Acrylic foldable IOLs > Silicone IOLs > PMMA IOLs. By examining the changes of surface properties as a function of temperature and incubation time, we found that acrylic foldable IOLs showed the largest increase in their hydrophilicity and reported the lowest surface roughness in comparison to other IOL groups. Coincidentally, using a newly established macromolecular dye imaging system to simulate cell migration between IOLs and LC, we observed that the amount of macromolecular dye infiltration between IOLs and LCs was in the following order: PMMA IOLs > Silicone IOLs > Acrylic foldable IOLs. These results support a new potential mechanism that body temperature, incubation time, surface hydrophilicity and smoothness of IOLs greatly contribute to their tight binding to LCs and such tight binding may lead to reduced IOL: LC space, cell infiltration, and thus PCO formation.

An in vitro system to investigate IOL: Lens capsule interaction

Posterior capsule opacification (PCO) is the most common complication associated with intraocular lens (IOL) implantation. Unfortunately, current in vitro models cannot be used to assess the potential of PCO due to their failure to simulate the posterior curvature of the lens capsule (LC) and IOL, a factor known to affect PCO pathogenesis in clinic. To overcome such a challenge, a new system to study IOL: LC interaction and potentially predict PCO was developed in this effort. It is believed that the interactions between an IOL and the lens capsule may influence the extent of PCO formation. Specifically, strong adhesion force between an IOL and the LC may impede lens epithelial cell migration and proliferation and thus reduce PCO formation. To assess the adhesion force between an IOL and LC, a new in vitro model was established with simulated LC and a custom-designed micro-force tester. A method to fabricate simulated LCs was developed by imprinting IOLs onto molten gelatin to create simulated three dimensional (3D) LCs with curvature resembling the bag-like structure that collapses on the IOL post implantation. By pushing the LC mold vertically downward, while measuring the change in position of the bending bar with respect to its start position, the adhesion force between the IOLs and LCs was measured. An in vitro system that can measure the adhesion force reproducibly between an IOL and LC with a resolution of ~1 μN was established in this study. During system optimization, the 10% high molecular weight gelatin produced the best LC with the highest IOL: LC adhesion force with all test lenses that were fabricated from acrylic foldable, polymethylmethacrylate (PMMA) and silicone materials. Test IOLs exerted different adhesion force with the 3D simulated LCs in the following sequence: acrylic foldable IOL > silicone IOL > PMMA IOL. These results are in good agreement with the clinical observations associated with PCO performance of IOLs made of the same materials. This novel in vitro system can provide valuable insight on the IOL: LC interplay and its relationship to clinical PCO outcomes.

Evaluation of Nd:YAG Laser Capsulotomy Rates in a Real-Life Population

Objective

The objective of this study was to assess the rate of posterior capsule opacification (PCO), under “real-life” conditions, as measured by rates of Nd:YAG laser intervention, rather than from a controlled study from which patients with conditions predisposing to PCO have been excluded.

Methods and Analysis

This was a retrospective, multicenter study in an unselected consecutive cohort of patients undergoing surgery for senile cataract. Patients aged 18 years and older, previously implanted with the CT LUCIA 611P IOL, were contacted at 12, 18 and 24 months to ascertain if they had received Nd:YAG laser treatment. There was an additional assessment at 36 months at the Austrian centre.

Results

A total of 200 patients were recruited at two centers. Laser capsulotomy rates were 4.5% at 1 year and 10% by year 2 and 12% by year 3. Three Nd:YAG capsulotomies, carried out at other external centers, were performed for reasons other than PCO, including astigmatism, epiretinal membrane and ARMD. If these patients are excluded, the true rate of Nd:YAG carried out for PCO at 1 year was 3.5% and at 2 years was 8.5%.

Conclusion

It is critical to ensure that Nd:YAG capsulotomies are being performed only for the correct clinical reason. Carrying out unnecessary procedures places the patient at risk of adverse events, is a cost to the healthcare system, and is likely to have no direct visual benefit for the patient. In PCO studies, it should be a requirement to document the fibrosis grade to confirm that Nd:YAG capsulotomy was correctly indicated.

Posterior Capsule Opacification With Two Hydrophobic Acrylic Intraocular Lenses: 3-Year Results of a Randomized Trial

PURPOSE

To compare the incidence and intensity of posterior capsule opacification (PCO) and neodymium-yttrium-aluminum-garnet (Nd:YAG) capsulotomy rates between 2 similar open-loop single-piece hydrophobic acrylic intraocular lenses (IOLs) that differ in the proprietary material characteristics and design features, over a period of 3 years.

DESIGN

Randomized, prospective, patient- and examiner-masked clinical trial with intraindividual comparison.

METHODS

Setting: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

PATIENT POPULATION

Eighty patients (160 eyes) had bilateral cataract surgery and received a Vivinex XY1 IOL in 1 eye and an AcrySof SN60WF IOL in the other eye.

OBSERVATION PROCEDURES

Follow-up examinations were performed 3 years after surgery. Digital retroillumination images were taken of each eye. The amount of PCO (score: 0-10) was assessed subjectively at the slit lamp and objectively using automated image analysis software (AQUA).

MAIN OUTCOME MEASURE

PCO score (scale, 0-10).

RESULTS

The mean objective PCO score of the Vivinex XY1 IOLs was 0.9 ± 0.8 compared to the PCO score of 1.4 ± 1.1 for the AcrySof SN60WF IOLs (P < .001). Three years postoperatively, 11.4% of patients had an Nd:YAG capsulotomy in the Vivinex XY1 eye and 18.6% had a capsulotomy in the AcrySof SN60WF eye (P = .23).

CONCLUSION

The new hydrophobic acrylic Vivinex XY1 IOL showed significantly lower PCO rates and lower YAG rates compared to the AcrySof SN60WF IOL. The interaction of various factors such as hydrophobic material, smooth optic surface, and sharp posterior optic edge plays a key role in PCO development.

5 year incidence of YAG capsulotomy and PCO after cataract surgery with single-piece monofocal intraocular lenses: a real-world evidence study of 20,763 eyes

OBJECTIVES

To evaluate the 3- and 5-year incidence of posterior capsule opacification (PCO) and neodymium-doped yttrium aluminium garnet (Nd:YAG) capsulotomy in patients following cataract surgery, comparing results for different single-piece acrylic hydrophilic and hydrophobic monofocal intraocular lens (IOL) models and other patient factors.

PATIENTS AND METHODS

Electronic medical record data collected from seven United Kingdom (UK) National Health Service (NHS) ophthalmology clinics for routine, age-related (≥65 years) cataract surgeries that implanted single-piece acrylic monofocal IOLs during 2010-2013 were used to calculate 3- and 5-year incidence of Nd:YAG and PCO. IOL models of Alcon Acrysof, AMO Tecnis, Bausch & Lomb (B & L) Akreos, LenStec Softec, and Rayner Flex were analyzed. Pairwise comparisons were conducted between AcrySof IOLs and other IOLs using Bonferroni adjustment for multiplicity. Multivariate analyses were conducted adjusting for known confounders.

RESULTS

The incidence of Nd:YAG capsulotomy ranged between 2.4-12.6% at 3 years and 5.8-19.3% at 5 years post-cataract surgery. Similarly, the incidence of PCO ranged between 4.7-18.6% at 3 years and 7.1-22.6% at 5 years. When comparing all of the single-piece IOLs, AcrySof demonstrated the lowest incidence rates for both PCO and Nd:YAG (P < 0.001 for each comparison). From adjusted logistic regression analysis, AcrySof were associated with lower 3- and 5-year odds of Nd:YAG and PCO incidence.

CONCLUSIONS

Following cataract surgery with single-piece monofocal IOLs different incidence rates of PCO were observed with different IOLs. AcrySof IOLs were associated with significantly lower incidence of PCO requiring Nd:YAG treatment over periods of 3 and 5 years.

An In Vitro Human Lens Capsular Bag Model Adopting a Graded Culture Regime to Assess Putative Impact of IOLs on PCO Formation

Purpose

To develop a culture regime for the in vitro human lens capsular bag model that better reflects clinical events following cataract surgery and to use this refined model to evaluate the putative impact of IOLs on PCO formation.

Methods

Capsulorhexis and lens extraction were performed on human donor eyes to generate capsular bags attached to the ciliary body by the zonules. Preparations were secured by pinning the ciliary body to a silicone ring and maintaining in 6 mL serum-free EMEM for 28 days or in a graded culture system (days 1-3, 5% human serum and 10 ng/mL TGFβ2; days 4-7, 2% human serum and 1 ng/mL TGFβ2; days 8-14, 1% human serum and 0.1 ng/mL TGFβ2; days 15-28, serum-free EMEM), which better mimics clinical changes. Preparations were monitored with phase-contrast and modified-dark-field microscopy. Cell coverage and light scatter were quantified using image analysis software. The transdifferentiation marker, α-SMA and matrix component, fibronectin were assessed by immunocytochemistry. To assess IOLs in the model, Alcon Acrysof or Hoya Vivinex IOLs were implanted in match-paired capsular bags.

Results

Match-paired experiments showed that graded culture enhanced growth, facilitated matrix contraction, increased transdifferentiation, and promoted matrix deposition relative to serum-free culture. The graded culture protocol was applied to match-paired bags implanted with a Hoya Vivinex or an Alcon Acrysof IOL. The Vivinex demonstrated a lag in growth across the posterior capsule. However, by day 28, coverage was similar, but light-scatter was greater with Acrysof implanted. Cell growth on the Acrysof IOL anterior surface was significantly greater than Vivinex.

Conclusions

The graded culture human capsular bag model serves as an excellent system to evaluate and develop intraocular lenses. The Hoya Vivinex IOL showed an overall better level of performance against postsurgical wound healing and PCO than the Alcon Acrysof using this model.

Edge profile of commercially available square-edged intraocular lenses: Part 2

PURPOSE

To analyze the sharpness of the posterior optic edge and edge thickness of intraocular lenses (IOLs) marketed with a square-edged profile.

SETTING

University of Brighton and Brighton and Sussex University Hospitals NHS Trust, Brighton, England.

DESIGN

Laboratory study.

METHODS

Fourteen square-edged 20.0 diopter IOLs were analyzed, including 9 hydrophobic IOLs (AF-1, AF-1 iSert, Clareon, EyeCee One Crystal, CT Lucia, Envista, EyeCee One, Vivinex iSert, and RayOne Hydrophobic) and 5 hydrophilic IOLs (Asphira, CT Asphina, Incise, Synthesis, and RayOne Hydrophilic). All the IOLs were scanned following a previously published standardized technique using environmental scanning electron microscopy. The posterior optic edges were scanned at a magnification of ×500 and ×200 to measure the radius of curvature of the posterior optic edges and the optic edge thickness.

RESULTS

The radius of curvature of the posterior optic edges ranged from 4.6 to 20.6 μm. Except for the Incise IOL (7.7 μm), all hydrophilic IOLs (Synthesis [10.6 μm], Asphira [13.7 μm], RayOne Hydrophilic [14.0 μm], CT Asphina [13.7 μm]) had a radius of curvature greater than 10.0 μm. For the hydrophobic IOLs, the radius of curvature was less than 10.0 μm for the Clareon (7.9 μm), EyeCee One Crystal (4.7 μm), Vivinex iSert (7.6 μm), and CT Lucia (4.6 μm), and greater than 10.0 μm for the Envista (19.7 μm), EyeCee One (13.7 μm), AF-1 iSert (19.7 μm), AF-1 (19.7 μm) and the RayOne Hydrophobic (20.6 μm). The Vivinex iSert (150.5 μm) and the Incise (218.2 μm) were the thinnest IOLs, and the RayOne Hydrophobic (375.8 μm) and RayOne Hydrophilic IOLs (477.1 μm) were the thickest of the hydrophobic and hydrophilic IOLs, respectively.

CONCLUSIONS

Commercially marketed square-edged IOLs still differed in the sharpness of the posterior optic edge. More hydrophobic IOLs have rounder edges than those studied 10 years ago. Variations in the edge profile of hydrophobic IOLs were greater compared with the hydrophilic IOLs.

Effects of grape seed extract, lutein, and fish oil on responses of canine lens epithelial cells in vitro

OBJECTIVE To determine the effects of grape seed extract (GSE), lutein, and fish oil containing omega-3 fatty acids on oxidative stress, migration, proliferation, and viability of lens epithelial cells (LECs). SAMPLE Lens capsules or cultured LECs obtained from canine cadavers. PROCEDURES An antioxidant reductive capacity assay was used to determine reducing capability of each substance. The LECs were cultured and incubated with various substances, including N-acetyl cysteine (NAC), when appropriate, and dimethyl sulfoxide (DMSO) as positive and vehicle control substances, respectively. A dichlorofluorescein assay was used to evaluate reactive oxygen species (ROS) production, and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine cell viability. Ex vivo posterior capsule opacification (PCO) was used to evaluate LEC migration and proliferation. RESULTS Antioxidant reductive effects of GSE surpassed those of NAC, lutein, and fish oil containing omega-3 fatty acids. The GSE reduced ROS production in LECs, compared with the DMSO vehicle control, whereas lutein was pro-oxidative. All test substances reduced cell viability. Ex vivo PCO was not altered by GSE, was decreased by lutein, and was increased by fish oil containing omega-3 fatty acids, compared with results for the DMSO vehicle control. CONCLUSIONS AND CLINICAL RELEVANCE Only GSE had significant antioxidant capabilities and reduced ROS production; however, no effect on ex vivo PCO was detected. Fish oil containing omega-3 fatty acids increased ex vivo PCO. No conclusions could be made regarding antioxidant effects of these substances on LECs. These findings suggested that the substances will not decrease PCO.

The Effects of Three-Piece or Single-Piece Acrylic Intraocular Lens Implantation on Posterior Capsule Opacification

Purpose

To evaluate the development of posterior capsule opacification (PCO) in patients implanted with 5.5 mm optics, single-piece or three-piece acrylic intraocular lens (IOL) in cataract surgery prospectively.

Methods

This study was carried out on 267 eyes of 249 patients implanted with three-piece, 5.5 mm optics, acrylic IOL and 252 eyes of 244 patients implanted with single-piece, 5.5 mm optics, acrylic IOL by phacoemulsification technique between September 2001 and February 2003. A total of 519 eyes of 493 patients were prospectively evaluated for PCO development during the 25-month period. All the patients were analyzed periodically with anterior segment retroillumination photography. The data provided were analyzed with chi-square method.

Results

The results between the two groups for PCO development were not statistically significant. However, there was a prominent opacification of the posterior capsule where the optic and haptic junction of IOL was positioned in some patients implanted with single-piece IOL. During the follow-up period, no patients implanted with either three-piece or single-piece acrylic IOL required Nd:YAG laser capsulotomy.

Conclusions

Biocompatibility and reduced rate of PCO development are among the leading features of new generation IOLs. The intracapsular implantation of 5.5 mm optics acrylic IOLs resulted in decreased incidence of PCO and therefore greater patient satisfaction. Further studies investigating the effects of IOL optics, haptic structure and length, capsulorrhexis size, and IOL material and design features on PCO development will clarify the subject.

Comparison of visual performance and after cataract formation between two monofocal aspheric intraocular lenses following phacoemulsification for senile cataract: A randomized controlled study

PURPOSE

Monofocal aspheric intraocular lenses (IOLs) provide better visual outcome compared to other available IOLs following cataract surgery. However, the imported IOLs are expensive and are not affordable by all subset of patients in low- to middle-income countries like India. The aim of this study is to compare the safety and efficacy of a relatively low cost indigenous IOL (Acriol EC) with an imported aspheric IOL (AcrySof IQ).

METHODS

A randomized controlled trial was conducted at a tertiary care centre. Two hundred and five eyes of 137 patients >45 years of age with uncomplicated age-related cataract were recruited. All cases underwent standard phacoemulsification and randomly assigned to one of the IOL implantations (Group I: AcrySof IOL; Group II: Acriol EC IOL). Primary outcome measure was best-corrected visual acuity (BCVA). Secondary outcomes included visual function (VF) score, spherical equivalent, contrast sensitivity, optical aberrations, and posterior capsular opacification. Independent t-test to compare two means; Mann-Whitney test; Pearson's Chi-square test, and McNemar's test were used for analyzing the nonparametric data such as incidence of posterior capsule opacification.

RESULTS

There was no significant difference in the mean postoperative BCVA at 1, 3, 6, and 12 months in either group (P > 0.05). The contrast sensitivity, wavefront aberrations, VF score, and posterior capsular opacification were comparable between the groups except for higher-order aberrations and spherical aberration, which were higher in Group II.

CONCLUSIONS

Acriol EC IOL provides visual outcomes comparable to other commonly used aspheric IOLs with comparable safety and efficacy at an affordable cost.

The Complexities of Negative Dysphotopsia

The appearance of a dark shadow in the temporal periphery, otherwise known as negative dysphotopsia, continues to be a problem for some patients after routine uncomplicated cataract surgery. Etiologies include type and design of intraocular lens (IOL), anatomical features and dimensions of the eye, pupil size, angle kappa, relationship of the optic to the anterior capsule, and the position of the optic/haptic junction of the IOL. Although the primary etiology remains controversial, it is clear that the cause is multifactorial. All of the factors should be considered when attempting to prevent or treat this phenomenon.

Negative dysphotopsia: A perfect storm

The objective of this review was to provide a summary of the peer-reviewed literature on the etiologies of negative dysphotopsia that occurs after routine cataract surgery. A search of PubMed, Google Scholar, and Retina Medical identified 59 reports. Negative dysphotopsia has been associated with many types of intraocular lenses (IOLs), including hydrophobic and hydrophilic acrylic, silicone, and 1-piece and 3-piece designs. Proposed etiologies include edge design, edge smoothness, edge thickness, index of refraction of the IOL, pupil size, amount of functional nasal retina, edema from the clear corneal incision, distance between the iris and IOL, amount of pigmentation of the eye, corneal shape, prominent globe and shallow orbit, and interaction between the anterior capsulorhexis and IOL. Treatments include a piggyback IOL, reverse optic capture, dilation of the pupil, constriction of the pupil, neodymium:YAG capsulotomy of the nasal portion of the anterior capsule, IOL exchange with round-edged optics, and time alone. This review summarizes the findings.

FINANCIAL DISCLOSURE

Dr. Henderson is a consultant to Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Bausch & Lomb, and Genzyme Corp. Neither author has a financial or proprietary interest in any material or method mentioned.

The effect of single-piece hydrophobic acrylic intraocular lenses on the development of posterior capsule opacification

PURPOSE

To evaluate the long-term effect of a single-piece hydrophobic acrylic intraocular lens (IOL), AcrySof SN60AT (Alcon Laboratories, Fort Worth, Texas, USA), on the development of posterior capsule opacification (PCO) 5 years postoperatively.

DESIGN

Prospective, observational, consecutive, case series.

METHODS

setting: Iladevi Cataract and IOL Research Center, Ahmedabad, India.

STUDY POPULATION

Three hundred and ninety eyes with uncomplicated age-related cataract were included. Patients with diabetes mellitus, glaucoma, high myopia, pseudoexfoliation, traumatic cataract, subluxated cataract, previous ocular surgeries, and allergy to dilating drops were excluded. intervention procedures: Digital retroillumination photographic documentation was performed and analyzed for PCO using Evaluation of Posterior Capsule Opacification software. The scores and areas were calculated.

MAIN OUTCOME MEASURES

PCO development and the influence of the anterior capsule cover (total on and part on) on the IOL optic was studied within the capsulorrhexis margin and the central 3.0 mm optic area.

RESULTS

There was a significant increase in PCO up to 3 years. No significant change in PCO was observed between 3 and 5 years within the capsulorrhexis margin and central 3.0 mm optic area. In the total on group, within the capsulorrhexis margin, significantly lower scores and areas were observed when compared with part-on scores and areas.

CONCLUSION

The increase in PCO up to 3 years was significant. Stabilization in PCO was observed between 3 and 5 years with no difference at 5 years. There was a low incidence of PCO in eyes with total anterior capsule cover over the IOL optic.

Experimental models for posterior capsule opacification research

Millions of people worldwide are blinded due to cataract formation. At present the only means of treating a cataract is through surgical intervention. A modern cataract operation involves the creation of an opening in the anterior lens capsule to allow access to the fibre cells, which are then removed. This leaves in place a capsular bag that comprises the remaining anterior capsule and the entire posterior capsule. In most cases, an intraocular lens is implanted into the capsular bag during surgery. This procedure initially generates good visual restoration, but unfortunately, residual lens epithelial cells undergo a wound-healing response invoked by surgery, which in time commonly results in a secondary loss of vision. This condition is known as posterior capsule opacification (PCO) and exhibits classical features of fibrosis, including hyperproliferation, migration, matrix deposition, matrix contraction and transdifferentiation into myofibroblasts. These changes alone can cause visual deterioration, but in a significant number of cases, fibre differentiation is also observed, which gives rise to Soemmering's ring and Elschnig's pearl formation. Elucidating the regulatory factors that govern these events is fundamental in the drive to develop future strategies to prevent or delay visual deterioration resulting from PCO. A range of experimental platforms are available for the study of PCO that range from in vivo animal models to in vitro human cell and tissue culture models. In the current review, we will highlight some of the experimental models used in PCO research and provide examples of key findings that have resulted from these approaches.

Optical coherence tomography for an in-vivo study of posterior-capsule-opacification types and their influence on the total-pulse energy required for Nd:YAG capsulotomy: a case series

Background

Posterior capsule opacification (PCO) is the most common post-operative complication associated with cataract surgery and is mostly treated with Nd:YAG laser capsulotomy. Here, we demonstrate the use of high-resolution spectral-domain optical coherence tomography (OCT) as a technique for PCO analysis. Additionally, we evaluate the influence of PCO types and the distance between the intraocular lens (IOL) and the posterior capsule (PC), i.e., the IOL/PC distance, on the total-pulse energy required for the Nd:YAG laser posterior capsulotomy.

Methods

47 eyes with PCO scheduled for the Nd:YAG procedure were examined and divided into four categories: fibrosis, pearl, mixed type and late-postoperative capsular bag distension syndrome. Using custom-made computer software for OCT image analysis, the IOL/PC distances in two dimensions were measured. The IOL/PC distances were compared with those of a control group of 15 eyes without PCO. The influence of the different PCO types and the IOL/PC distance on the total-pulse energy required for the Nd:YAG procedure was analyzed.

Results

The total-pulse energy required for a laser capsulotomy differs significantly between PCO types (p = 0.005, Kruskal-Wallis test). The highest energy was required for the fibrosis PCO type, followed by mixed, pearl and late-postoperative capsular bag distension syndrome. The IOL/PC distance also significantly influenced the total-pulse energy required for laser capsulotomy (p = 0.028, linear regression). Lower total-pulse energy was expected for a larger IOL/PC distance.

Conclusions

Our study indicates that the PCO types and the IOL/PC distance influence the total-pulse energy required for Nd:YAG capsulotomy. The presented OCT method has the potential to become an additional tool for PCO characterization. Our results are important for a better understanding of the photodisruptive mechanisms in Nd:YAG capsulotomy.

Posterior capsule opacification and neodymium:YAG rates with 2 single-piece hydrophobic acrylic intraocular lenses: three-year results

PURPOSE

To compare the incidence and intensity of posterior capsule opacification (PCO) between 2 similar 1-piece foldable hydrophobic acrylic intraocular lenses (IOLs) over 3 years.

SETTING

Department of Ophthalmology, Medical University Vienna, Vienna, Austria.

DESIGN

Randomized prospective patient- and examiner-masked clinical trial with intraindividual comparison.

METHODS

Patients with bilateral age-related cataract had cataract surgery and implantation of a Tecnis ZCB00 continuous-optic-edge IOL in 1 eye and an Acrysof SA60AT interrupted-optic-edge IOL in the other eye. Postoperative examinations were performed at 6 months and 3 years. Digital retroillumination images were taken of each eye. The amount of PCO (score 0 to 10) was assessed subjectively at the slitlamp and objectively using automated image-analysis software.

RESULTS

The study comprised 54 patients (108 eyes). The mean objective PCO score was 1.3 ± 1.7 (SD) for the continuous-optic-edge IOLs and 0.9 ± 1.3 for the interrupted-optic-edge IOLs (P=.10). Three years postoperatively, a neodymium:YAG (Nd:YAG) capsulotomy was performed in 26.1% of eyes with the continuous-optic-edge IOL and 21.7% with the interrupted-optic-edge IOL (P=.56). There was no significant difference in corrected distance visual acuity, capsulorhexis–IOL overlap, capsule folds, or anterior capsule opacification 3 years after surgery.

CONCLUSIONS

Both IOLs had comparable PCO and Nd:YAG rates 3 years postoperatively. The optimized barrier function of the continuous-optic-edge IOL and the material properties of the interrupted-optic-edge IOL seemingly outbalanced the effect on lens epithelial cell migration and proliferation beneath the optic.

Aggregation states of polystyrene at nonsolvent interfaces

The aggregation states of polystyrene (PS) thin films at interfaces with nonsolvents such as water, methanol, and hexane were examined by specular neutron reflectivity and sum-frequency generation vibrational spectroscopy. The density profiles of the PS thin films along the direction normal to the interface with water and methanol were comparable to that in air. However, this was not the case for the film in hexane exhibiting a diffuse interfacial layer due to swelling. Also, the local conformation of PS in the outermost region of the films was quite sensitive to the surrounding environment and consequently responded to a change in its environment. This was the case for typical nonsolvents such as water and methanol. The extent of the conformational change might be explained in terms of the interfacial energy.

Non-invasive detection of early retinal neuronal degeneration by ultrahigh resolution optical coherence tomography

Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early stages of neuronal degeneration. Using ultrahigh resolution (UHR) OCT imaging at 800 nm (spectral width 140 nm) we developed a robust method of OCT image analyses, based on spatial wavelet and texture-based parameterisation of the image speckle pattern. For the first time we show that this approach allows the non-invasive detection and quantification of early apoptotic changes in neurons within 30 min of neuronal trauma sufficient to result in apoptosis. We show a positive correlation between immunofluorescent labelling of mitochondria (a potential source of changes in cellular optical contrast) with changes in the texture of the OCT images of cultured neurons. Moreover, similar changes in optical contrast were also seen in the retinal ganglion cell- inner plexiform layer in retinal explants following optic nerve transection. The optical clarity of the explants was maintained throughout in the absence of histologically detectable change. Our data suggest that UHR OCT can be used for the non-invasive quantitative assessment of neuronal health, with a particular application to the assessment of early retinal disease.

Effect of side-chain carbonyl groups on the interface of vinyl polymers with water

The nature of the polymer-water interface in the poly(methyl 2-propenyl ether) (PMPE)-water model system is investigated by sum-frequency generation spectroscopy, which at the moment gives the best depth resolution among available techniques. PMPE, synthesized via living cationic polymerization, is structurally similar to poly(methyl methacrylate) (PMMA) except for lacking a carbonyl group. We here probe the polymer local conformation as well as the aggregation states of water at the interface. Comparing the results of our measurements to the PMMA-water system, the effect of a carbonyl group on the water structure at the interface is discussed. This knowledge should be crucial to the design and construction of highly functionalized polymer interfaces for bioapplications.

Influence of a variable overall diameter hydrophilic acrylic sharp-edged single-piece intra-ocular lens on capsule opacification one year after surgery

BACKGROUND

To investigate the influence of the overall intraocular lens (IOL) diameter on posterior capsule opacification (PCO) formation.

METHODS

In this prospective randomized clinical trial, 124 eyes of 62 patients with bilateral age-related cataract were included. Each patient received a Corneal A501D IOL in one eye and a Corneal J501D IOL in the fellow eye. Best corrected visual acuity (BCVA) and digital slitlamp photographs were taken a 1 h, 1 week, 1, 3, 6 and 12 months postoperatively. The amount of PCO was assessed subjectively at the slitlamp and objectively using automated image-analysis software.

RESULTS

We found a mean BCVA of 0.81 ± 0.2 for the Corneal A501D group and 0.79 ± 0.21 for the Corneal J501D group. There was no significant difference 12 months after surgery between the two IOLs (p > 0.05). Objective PCO assessment resulted in a mean PCO score (scale 0-10) of 1.65 ± 1.71 was found for the Corneal J501D group and a score of 1.54 ± 1.64 was found for the Corneal A501D group (p > 0.05). The subjective PCO assessment at 1 year resulted in a mean PCO score of 2.0 ± 1.74 in the Corneal J501D group and 2.13 ± 1.64 in the Corneal A501D group (p > 0.05).

CONCLUSION

Both investigated IOLs showed good clinical performance regarding PCO and BCVA. Our study suggests that the use of an IOL with variable total diameter seems not to influence the rate of PCO formation.

Neodymium:yttrium-aluminum garnet capsulotomy rates after combined cataract surgery with implantation of a 4% water content hydrophobic acrylic intraocular lens and vitrectomy

BACKGROUND

The purpose of this study was to examine neodymium:yttrium-aluminum garnet (Nd:YAG) capsulotomy rates after combined cataract surgery with implantation of a three-piece 4% water content hydrophobic acrylic intraocular lens (X-70, Eternity®) and vitrectomy, and compare diabetic retinopathy with nondiabetic retinopathy.

METHODS

Nd:YAG capsulotomy rates were evaluated for 72 eyes of 72 patients with diabetic retinopathy and 81 eyes of 81 patients with nondiabetic retinopathy (50 eyes with retinal detachment, 13 eyes with macular hole, nine eyes with epiretinal membrane, seven eyes with branch retinal vein occlusion, and two eyes with uveitis) who underwent combined cataract surgery and vitrectomy and implantation of X-70.

RESULTS

Two years after combination surgery, four of 72 eyes (5.6%) in the diabetic retinopathy group and four of 81 eyes (5.0%) in the nondiabetic retinopathy group required Nd:YAG capsulotomies. Kaplan-Meier survival analysis showed no statistically significant differences between the two groups (P=0.30, Mantel-Cox log-rank test).

CONCLUSION

The rate of Nd:YAG capsulotomy did not significantly differ between diabetic retinopathy and nondiabetic retinopathy after combined cataract surgery with implantation of the X-70 and vitrectomy. X-70 is an acceptable intraocular lens for patients undergoing combined cataract surgery and vitrectomy.

Posterior capsule opacification with 3 intraocular lenses: 12-year prospective study

PURPOSE

To compare posterior capsule opacification (PCO) with 3 intraocular lenses (IOLs) 12 years postoperatively.

SETTING

St. Erik Eye Hospital, Stockholm, Sweden.

DESIGN

Randomized clinical trial.

METHODS

Patients having unilateral standard phacoemulsification were randomized to implantation of a round-edged heparin-surface-modified (HSM) poly(methyl methacrylate) (PMMA) IOL, a round-edged silicone IOL, or a sharp-edged hydrophobic acrylic IOL. The neodymium:YAG (Nd:YAG) capsulotomy rates and timing from surgery were recorded. Survival analysis was used to compare Nd:YAG rates. Retroillumination images were taken to evaluate PCO.

RESULTS

After 12 years, there was no significant difference in the fraction or severity of PCO between the silicone IOL and acrylic IOL. The HSM PMMA IOL had a significantly higher PCO fraction than the silicone IOL (P<.05), but not more than the acrylic IOL. There was no difference in PCO severity between the HSM PMMA IOL and the other 2 IOLs. The silicone IOL had higher median capsulotomy-free survival (>150 months) than the acrylic IOL (108 months) and the HSM PMMA IOL (53 months). Overall survival without Nd:YAG capsulotomy did not differ between the acrylic and silicone IOLs or between the silicone and HSM PMMA IOLs; however, overall survival was significantly better with the acrylic IOL than with the HSM PMMA IOL (P<.001).

CONCLUSIONS

After 12 years, there was no difference in PCO or overall survival without capsulotomy between the acrylic IOL and the silicone IOL. The HSM PMMA IOL had a significantly higher PCO fraction than the silicone IOL and lower overall survival than the acrylic IOL.

Intraocular lens-edge design and material factors contributing to posterior-capsulotomy rates: comparing Hoya FY60aD, PY60aD, and AcrySof SN60WF

PURPOSE

To compare neodymium-doped yttrium aluminum garnet laser posterior capsulotomy (LPC) rates between the Hoya FY60AD, Hoya PY60AD, and Alcon AcrySof SN60WF intraocular lenses (IOLs) after routine cataract surgery.

METHODS

In this retrospective comparative study, patients undergoing uncomplicated cataract surgery over a 3-year period were included, and those subsequently undergoing LPC were identified from laser clinic records. LPC rates at 2 years postoperatively were compared between the round-edged Hoya FY60AD, the newer sharp-edged Hoya PY60AD three-piece IOLs, and the one-piece AcrySof SN60WF IOL.

RESULTS

A total of 1,265 cataract operations were included, and 49 eyes (3.9%) underwent LPC within 2 years of surgery. Twenty-eight of 315 eyes (8.9%) implanted with the FY60AD underwent LPC by 2 years, compared to eleven of 254 (4.3%) with the newer sharp square-edged PY60AD and ten of 696 (1.4%) with the one-piece SN60WF (P < 0.05, Chi-squared analyses).

CONCLUSIONS

The newer, sharper-edged Hoya PY60AD IOL has a lower LPC rate than the Hoya FY60AD IOL at 2 years post-cataract surgery. The one-piece AcrySof SN60WF has a lower LPC rate than both the three-piece Hoya IOLs in the same time period postoperatively. Variations in IOL-edge design and material effect may have contributed to the different rates observed.

A randomized, single-center study of equivalence of 2 intraocular lenses used in cataract surgery

PURPOSE

To compare the outcomes of 2 intraocular lenses (IOLs) for the treatment of age-related cataracts.

DESIGN

Prospective, randomized trial.

PARTICIPANTS

Patients with age-related cataracts were recruited and randomized to receive phacoemulsification and implantation of either the AcrySof SA60AT lens (Alcon, Inc, Fort Worth, TX) or the low-cost Tecsoft Flex lens (Fred Hollows Foundation, Tilganga, Nepal). A total of 300 patients were available for description and analysis (148 in the AcrySof group and 152 in the Tecsoft group).

METHODS

Patients underwent phacoemulsification and implantation of the AcrySof SA60AT lens or the Tecsoft Flex lens. They were followed up and examined at baseline, 1 week, 1 month, 6 months, and 12 months after cataract surgery.

MAIN OUTCOME MEASURES

Uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BDVA), incidence of posterior capsule opacification (PCO), Visual Function Index questionnaire results, and safety of the implanted IOLs.

RESULTS

No significant difference (P>0.05) was found in UDVA and BDVA after surgery between the 2 groups. The equivalence test of the 95% confidence intervals showed that both lenses had an equal improvement of UDVA and BDVA as well as similar rates of PCO after cataract surgery. There was no significant difference between the 2 groups with regard to visual functioning or the incidence of adverse surgical events during (P>0.05) or after (P>0.05) the surgery.

CONCLUSIONS

The Tecsoft Flex IOL is a low-cost suitable alternative that is similar to the AcrySof IOL in terms of safety and visual outcomes.

Long-term effect of surface light scattering and glistenings of intraocular lenses on visual function

PURPOSE

To investigate the long-term effect of surface light scattering and glistenings of various intraocular lenses (IOLs) on visual function and optical aberrations after cataract surgery.

DESIGN

Case-control study.

METHODS

Thirty-five eyes that underwent implantation of a hydrophobic acrylic, silicone, or polymethyl methacrylate (PMMA) IOL more than 10 years ago were recruited. The scattering light intensity of the surface and internal matrix of the optic was measured using Scheimpflug photography. Visual acuity (VA) was measured using VA charts, and contrast VA and that with glare (glare VA) were examined using a contrast sensitivity tester. Ocular higher-order aberrations (HOAs) were measured using a Hartmann-Shack aberrometer.

RESULTS

Mean scattering light intensity of the surface and internal matrix of the optic was significantly higher in the acrylic group than in the silicone and PMMA groups (P < .0001). Mean uncorrected VA, photopic and mesopic contrast VA and glare VA, and HOAs did not differ significantly among groups, although mean corrected VA in the acrylic group was significantly better than that in the other groups (P = .0023). Scattering light intensity of the surface and internal matrix did not correlate with VA, contrast VA, or glare VA, and did not correlate with ocular and internal optic HOAs in the acrylic group.

CONCLUSIONS

At more than 10 years postoperatively, visual function, including contrast sensitivity, and ocular HOAs were comparable among eyes that received acrylic, silicone, and PMMA IOLs. Surface scattering and glistenings with the acrylic IOLs were not significantly correlated with visual function and optical aberrations.

Intraocular lens and capsule opacification with hydrophilic and hydrophobic acrylic materials

PURPOSE

To report posterior capsular opacification in acrylic intraocular lenses.

METHODS

Retrospective review of notes of patients with cataract surgery involving implantation of a hydrophilic acrylic intraocular lens (IOL) (MDR SC-60B-0UV) in at least one eye. This was done as a retrospective audit for clinical risk following adverse event reports, regarding MDR SC-60B-0UV intraocular lens, were published. Data regarding the pre- and post-operative visual acuity, ocular co-morbidity, posterior capsular thickening, Nd-YAG capsulotomy, final visual acuity, and changes in the lens clarity in both eyes were noted from the clinical notes.

RESULTS

45 patients and 90 eyes were identified. Posterior capsular opacification (PCO) as determined by slit-lamp examination was 40% for the hydrophilic IOL (SC-60B-0UV) and 8% for the contra-lateral eye (hydrophobic IOL). In 22 eyes opacification of the SC-60-0UV IOL was observed at slit-lamp examination (44%).

CONCLUSION

The hydrophilic acrylic IOL (SC60B-0UV) appears to have a high incidence of PCO.

Effect of intraocular lens asphericity on posterior capsule opacification between two intraocular lenses with same acrylic material: a fellow-eye study

PURPOSE

To evaluate intra-individual differences in posterior capsule opacification (PCO) and visual performance between spherical AcrySof SN60AT and an aspheric AcrySof SN60WF intraocular lens (IOL) with a posterior aspheric surface, both of which are made of same hydrophobic acrylic material.

SETTING

Ophthalmology Department, St Thomas' Hospital, London, UK.

METHODS

In this prospective randomized, fellow-eye comparison, an aspheric IOL, which is 9% thinner in comparison with the spherical IOL, was randomized to the first eye of 47 patients and fellow-eye surgery was performed within 3 weeks. Follow-up was at 1, 3, 6, 12 and 24 months. Corrected logMAR visual acuity (CDVA) was measured at 100% and 9% contrast. After pupil dilation, digital retroillumination photographs were taken and the mean PCO percentage was calculated using poco software at each follow-up visit.

RESULTS

At 1, 3, 6, 12 and 24 months, 47 (94 eyes), 44 (88 eyes), 42 (84 eyes) and 41 (82 eyes) patients were followed-up respectively. Hundred per cent and 9% of LogMAR CDVA was not significantly different between the two IOLs (p = NS at all time-points). Percentage area PCO scores (mean ± SD) at 1, 3, 6, 12 and 24 months with the spherical IOL was 5.82 ± 9.89, 7.76 ± 16.83, 7.21 ± 12.46, 9.29 ± 18.25 and 14.39 ± 25.42, respectively, and with an aspheric IOL was 8.91 ± 12.79, 5.97 ± 10.32, 5.15 ± 7.92, 7.68 ± 11.18 and 12.18 ± 20.10, respectively (p = NS at all time-points).

CONCLUSIONS

Posterior capsule opacification was not significantly different between the spheric and aspheric IOLs in this fellow-eye, randomized comparison. Additional asphericity on the existing model of IOL does not influence PCO performance.

Comparison of posterior capsule opacification with hydrophobic acrylic and hydrophilic acrylic intraocular lenses

PURPOSE

To compare posterior capsule opacification (PCO) 3 years postoperatively in contralateral eyes with a single-piece hydrophobic acrylic and 1 of 2 single-piece hydrophilic acrylic intraocular lenses (IOLs) with different configurations.

SETTING

Iladevi Cataract and IOL Research Institute, Ahmedabad, India.

DESIGN

Prospective randomized clinical trial.

METHODS

A hydrophobic Acrysof (hydrophobic group) or a hydrophilic C-flex (hydrophilic group C) or Akreos Adapt IOL (hydrophilic group A) was randomized for implantation in the fellow eye or vice versa of each patient. The Evaluation of Posterior Capsule Opacification (EPCO) area, EPCO score, and neodymium:YAG (Nd:YAG) capsulotomy rates were compared using digital photographs.

RESULTS

The study enrolled 68 patients. Although there was no significant difference at 1 month, the median EPCO score was statistically significantly lower in the hydrophobic group than in hydrophilic group C (P = .00) and hydrophilic group A (P = .000) at 3 years. There were no significant differences in the median EPCO area at 1 month; however, the area was statistically significantly less in the hydrophobic group than in hydrophilic group C and hydrophilic group A at 3 years (both P = .000). Four (12.9%) of 31 eyes in hydrophilic group C and 5 (16%) of 31 eyes in hydrophilic group A required an Nd:YAG capsulotomy; no eye in the hydrophobic group required a capsulotomy (P = .04 and P = .02, respectively).

CONCLUSION

Posterior capsule opacification was significantly less with the Acrysof hydrophobic acrylic IOL at 3 years.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Surface roughness of intraocular lenses with different dioptric powers assessed by atomic force microscopy

PURPOSE

To analyze the optic surface roughness and morphology of 2 types of hydrophobic acrylic intraocular lenses (IOLs) with various dioptric powers using atomic force microscopy (AFM).

SETTING

Technical University of Cluj-Napoca, Faculty of Mechanics, Cluj-Napoca, Romania.

METHODS

Atomic force microscopy was used to characterize the topography of 2 types of hydrophobic acrylic IOLs from a single manufacturer (SN60AT and SA30AL) with dioptric powers ranging from 10.0 diopters (D) to 30.0 D. The AFM analysis was performed in contact mode using a V-shaped silicon nitride cantilever with a pyramidal tip curvature of 15 nm and a nominal spring constant of 0.2 N/m. Detailed surface characterization of the IOL optic was obtained using 6 quantitative parameters provided by the AFM software.

RESULTS

Five of 6 roughness parameters indicated statistically significant differences (P<.05) between IOLs with different dioptric powers, with the 10.0 D IOL in both models providing the smoothest optic surface. Between models with the same dioptric power, the SN60AT model had lower values of each surface roughness parameter than the SA30AL model.

CONCLUSIONS

Atomic force microscopy was an accurate tool for assessing the surface properties of IOL optics. Manufacturing processes were responsible for introducing detectable differences in the topography of IOL biomaterials with identical copolymer constituents but different dioptric powers. Nanometric analysis may assist IOL manufacturers in developing IOLs with optimal surface characteristics.

Functional assessment of accommodating intraocular lenses versus monofocal intraocular lenses in cataract surgery: metaanalysis

PURPOSE

To compare accommodating intraocular lens (IOLs) and monofocal IOLs in restoring accommodation in cataract surgery.

SETTING

Dartmouth Medical School and Department of Ophthalmology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA.

METHODS

In this metaanalysis, 2 researchers independently extracted data, assessed trial quality, and contacted authors for missing information. Because of measurement-scale variations, outcomes were pooled for distance-corrected near visual acuity (DCNVA) as standardized mean differences with 95% confidence intervals [CIs] and anterior displacement of the lens as weighted mean differences (95% CI).

RESULTS

The metaanalysis comprised 12 randomized controlled studies of 727 eyes. Based on 10 studies that compared DCNVA, accommodating IOLs were favored but failed the test of heterogeneity (I(2) = 94%). Pooling the 6 homogeneous trials (I(2) = 43%) showed no difference (standardized mean difference, -0.16; 95% CI, -0.56 to 0.25). Heterogeneity could not be explained by any characteristic of the study population or methodology. Based on 4 studies that evaluated pilocarpine-induced IOL shift, there was a significant anterior compared with the control (weighted mean difference, 95% CI, -0.36 - 0.47 to -0.24]), although the studies were heterogeneous (I(2) = 58%). Three of 5 studies mentioning posterior capsule opacification (PCO) reported increased rates in the accommodating IOL group postoperatively.

CONCLUSIONS

There was no clear evidence of near acuity improvement despite statistically significant pilocarpine-induced anterior lens displacement. Further randomized controlled studies with standardized methods evaluating adverse effects (eg, PCO) are needed to clarify the tradeoffs.

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.

Comparison of posterior capsule opacification development with 3 intraocular lens types: five-year prospective study

PURPOSE

To compare the effects of hydrophobic acrylic, silicone, and heparin-surface-modified poly(methyl methacrylate) (HSM PMMA) intraocular lenses (IOLs) on posterior capsule opacification (PCO).

METHODS

In this 5-year prospective study, the same surgeon performed standard phacoemulsification in patients who were randomized to implantation of a round-edged HSM PMMA IOL (809C), a round-edged silicone IOL (SI-40NB), or a sharp-edged hydrophobic acrylic IOL (AcrySof MA60BM). The neodymium:YAG capsulotomy rate was recorded. To evaluate PCO and the position of the anterior capsulorhexis, retroillumination digital photographs were taken 5 years postoperatively and analyzed using the POCOman computer-analysis system.

RESULTS

After 5 years, there was no significant difference in the fraction or severity of PCO between the silicone IOLs and acrylic IOLs (both P =1.0). The silicone IOL group had a significantly higher capsulotomy rate (29%) than the acrylic IOL group (8%) (P=.0068). The HSM PMMA IOL group had a significantly higher PCO fraction, severity, and capsulotomy rate (54%) than the silicone and acrylic groups. In all eyes, the fraction (P=.0076) and severity (P=.0081) of PCO were statistically significantly higher when the anterior capsulorhexis was partly decentered than when it was completely on the optic; within each IOL group, there was no significant difference.

CONCLUSION

After 5 years, there was no significant difference in the semiquantitative evaluation of PCO between the sharp-edged acrylic IOL and round-edged silicone IOL. Eyes with the HSM PMMA IOL had more PCO than eyes with the other IOLs.

Analysis of surface whitening of extracted hydrophobic acrylic intraocular lenses

PURPOSE

To identify the cause of light scattering on the surface (ie, whitening) of extracted AcrySof intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, Dokkyo Medical University, Tochigi, Japan.

METHODS

Dislocated IOLs extracted from 3 patients were stored and the IOL surfaces examined under light microscopy. The effect of whitening on visual function was evaluated by measuring light transmission with a spectrophotometer. To determine the cause of opacification, the IOLs were examined for calcium phosphate deposits using an electron probe X-ray microanalyzer. The IOL surface, including the presence of organic deposits and evidence of hydrolysis, was also examined by Fourier-transform infrared spectrophotometry. The IOLs were then dried, immersed again in physiological saline, and serially examined for changes in opacification.

RESULTS

The optic surfaces of all IOLs had opacification due to whitening. Light transmission in the visible range of 360 to 800 nm was 4% less than that of unused IOLs. The X-ray microanalysis showed no calcium phosphate deposits. Fourier-transform infrared spectrophotometry of the IOL optic material showed no evidence of hydrolysis. Opacification disappeared after the IOLs were dried and then reappeared over time when the IOL was immersed again in physiologic saline.

CONCLUSIONS

The findings strongly suggest that whitening of the hydrophobic acrylic IOL was due to trace water molecules that infiltrate the optic. Within the 3-dimensional network of the polymeric lens material, the molecules are too small to form observable voids but can form water aggregates of sufficient size to scatter visible light, causing opacification (ie, whitening).