Square-edged Intraocular Lenses Research Articles

Intraocular lens selection in diabetic patients: How to increase the odds for success.

The incidence of cataracts is significantly higher in diabetic individuals, particularly in younger age groups, with rates quadrupled in those under 65 and doubled in those over 65 compared to non-diabetics. Cataract surgery in diabetic patients poses many challenges: Poor epithelial healing, decreased corneal sensitivity, increased central corneal thickness, decreased endothelial cell count, variable topography, poor pupillary dilatation, anterior capsular phimosis, posterior capsular opacification (PCO), chances of progression of diabetic retinopathy (DR), zonular weakness, and vitreous prolapse and diabetic macular edema. Selection of an appropriate intraocular lens (IOL) is crucial for visual rehabilitation and monitoring DR. The choice of IOL in diabetic cataract patients is a challenging scenario. Square-edge IOLs are favored for their capacity to mitigate PCO, whereas hydrophilic counterparts may incur calcification in the setting of proliferative DR. The advisability of premium IOLs for achieving spectacle independence warrants judicious evaluation, particularly in the presence of advanced retinopathy. Optimal IOL placement within the capsular bag is advocated to minimize postoperative complications. Rigorous preoperative assessment and informed patient counseling regarding IOL options are indispensable for optimizing surgical outcomes. This review article covers various aspects regarding the choice of IOLs in different case scenarios and complications in the diabetic population.

An Evaluation of the Inhibition Effects of Cell Migration of Aspirin Soaking 360°Square-Edge Intraocular Lens in an in Vitro Lens Capsule Model

ABSTRACT Purpose This study performs to evaluate the Hydrophobic and Hydrosmart 360°square-edge intraocular lens drug delivery of Aspirin using an in vitro lens capsular model. Methods Cell counting kit-8 assay was used to calculate 50% inhibiting concentration values in both SRA01/04 and HLE-B3 cells. Hoechst staining and transwell assay were used to detect cell proliferation and cell migration. The in vitro lens capsule model was established mainly with a special transwell-col and cell climbing sheet, in which an intraocular lens and the TGF-β2 were added. The ultraviolet spectrophotometer was used to measure the drug concentrations released in vitro. Cell-exclusion zone assay was used to detect the cell migration in the in vitro capsular model. Results It shows that cell morphology and distribution of SRA01/04 in the in vitro lens capsular model were closer to those in vivo. The results revealed that there could be significant inhibiting effects on cell migration of the hydrosmart intraocular lens with a sustained drug release in vitro in 7 days, while the hydrophobic intraocular lens drug delivery of Aspirin was mainly performed only from day 1 to day 3. Conclusions Results showed the developed hydrosmart intraocular lens could release Aspirin continuously in vitro to inhibit the cell migration of lens epithelial cells.

Posterior Capsule Opacification after Cataract Surgery in Children Over Five Years of Age with Square-edge Hydrophobic versus Hydrophilic Acrylic Intraocular Lenses: A Prospective Randomized Study

OBJECTIVE:To compare the effects of hydrophobic and hydrophilic materials in square-edged acrylic intraocular lenses (IOLs) on the development of posterior capsule opacification (PCO) after pediatric cataract surgery.METHODS:Patients were randomly assigned to group 1 (hydrophobic acrylic square-edged IOLs; 13 eyes) or group 2 (hydrophilic acrylic square-edged IOLs; 13 eyes). The study evaluated PCO rates using Evaluation of Posterior Capsule Opacification (EPCO) 2000 software at one, three, six and 12 months postoperatively. Postoperative measurements also included corrected distance visual acuity (CDVA), neodymium:yttrium‐aluminum‐garnet (Nd:YAG) capsulotomy and postoperative complications other than PCO.RESULTS:Both groups had significant increases in PCO rates after one year. Comparison of the groups showed no significant differences in the EPCO scores at three (group 1, 0.007±0.016 vs group 2, 0.008±0.014; p=0.830), six (group 1, 0.062±0.103 vs group 2, 0.021±0.023; p=0.184), or twelve months postoperatively (group 1, 0.200±0.193 vs group 2, 0.192±0.138; p=0.902). We also found no significant group differences regarding the change (delta, Δ) in EPCO scores between three and six months (group 1, 0.055±0.09 vs group 2, 0.013±0.02; p=0.113) or between six and twelve months postoperatively (group 1, 0.139±0.14 vs group 2, 0.171±0.14; p=0.567). Twenty-three percent of patients required Nd:YAG capsulotomy at the twelve-month visit.CONCLUSIONS:No differences in PCO rates were found between hydrophobic and hydrophilic acrylic square-edged IOLs in children between five and twelve years of age at one year of follow-up.

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

To analyze the sharpness of the posterior optic edge and edge thickness of intraocular lenses (IOLs) marketed with a square-edged profile. University of Brighton and Brighton and Sussex University Hospitals NHS Trust, Brighton, England. Laboratory study. 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. The radius of curvature of the posterior optic edges ranged from 4.6 to 20.6μm. Except for the Incise IOL (7.7μm), all hydrophilic IOLs (Synthesis [10.6μm], Asphira [13.7μm], RayOne Hydrophilic [14.0μm], CT Asphina [13.7μm]) had a radius of curvature greater than 10.0μm. For the hydrophobic IOLs, the radius of curvature was less than 10.0μm for the Clareon (7.9μm), EyeCee One Crystal (4.7μm), Vivinex iSert (7.6μm), and CT Lucia (4.6μm), and greater than 10.0μm for the Envista (19.7μm), EyeCee One (13.7μm), AF-1 iSert (19.7μm), AF-1 (19.7μm) and the RayOne Hydrophobic (20.6μm). The Vivinex iSert (150.5μm) and the Incise (218.2μm) were the thinnest IOLs, and the RayOne Hydrophobic (375.8μm) and RayOne Hydrophilic IOLs (477.1μm) were the thickest of the hydrophobic and hydrophilic IOLs, respectively. Commercially marketed square-edged IOLs still differed in the sharpness of the posterior optic edge. More hydrophobic IOLs have rounder edges than those studied 10years ago. Variations in the edge profile of hydrophobic IOLs were greater compared with the hydrophilic IOLs.

Three-Dimensional Morphology Study of Capsule in Pseudophakic Eyes with High-Speed Swept-Source Optical Coherence Tomography

ABSTRACTPurpose: To study the capsule morphology in pseudophakic eyes on the three-dimensional level using high-speed swept-source optical coherence tomography (SSOCT).Methods: This study collected patients with age-related cataract and divided them into two groups according to the anterior capsule and intraocular lens (IOL) optic relationship: total anterior capsule overlap (360°, Group-T) and partial anterior capsule overlap (<360°, Group-P). One standard SSOCT radial scanning was performed in all eyes at 1 day, 1 week, 1 month, and 3 months postoperatively.Results: Thirty-two eyes from 25 patients were enrolled in the Group-T and 17 eyes from 13 patients in the Group-P. No eyes achieved complete adhesion between IOL optic and posterior capsule at 1 day after the surgery. However, the rate of complete adhesion was low (15/49, 30.6%) even at 3 months postoperatively and there was no statistically difference between Group-T and Group-P (21.9% vs. 47.1%, P > 0.05). At 1 day, 1 week, 1 month, and 3 months after the surgery, the capsule bend index (CBI) in the Group-T was 0.02 ± 0.09, 1.35 ± 1.48, 3.60 ± 0.54, and 3.88 ± 0.19, respectively. CBI rises linearly during the first month and the rise goes stable relatively with the great reduction of standard deviation in the following 2 months (All P < 0.05). The anterior capsule opening area and diameter were both reduced in the first month, and then they both became stable.Conclusions: With square-edge IOL, posterior capsule opacification risk is still high in most eyes at 3 months postoperatively for the complete adhesion of posterior capsule and IOL was only achieved in 30.6% eyes. IOL-in-bag may be driven by the significant capsule bag changes especially in the first month postoperatively.

Recurrent Vitreous Hemorrhage Secondary to Sulcus Positioning of a One-Piece Acrylic Intraocular Lens Haptic: Report of 3 Cases and Management With Retrocapsular Haptic Repositioning

Three pseudophakic patients presented with recurrent, unilateral vitreous hemorrhage, one of which also had uveitis, glaucoma, and hyphema, consistent with “uveitis–glaucoma–hyphema (UGH)-Plus” syndrome. Arcuate transillumination defects secondary to inadvertent placement of 1 intraocular lens (IOL) haptic in the sulcus were identified in each case. The second haptic and optic were located in the capsular bag. The IOLs were all single-piece foldable acrylic lenses with square-edge haptic design. Surgical repositioning of the malpositioned haptic from the sulcus to the retrocapsular space resulted in the resolution of the recurrent vitreous hemorrhage. This series highlights the fact that recurrent vitreous hemorrhage secondary to iris chafing, with or without UGH, may occur in cases where a square-edge IOL haptic is placed in the sulcus. Vitrectomy with repositioning of the malpositioned IOL is a simple alternative to IOL exchange in these cases.

Square-edge intraocular lens versus conventional round-edge intraocular lens in prevention of posterior capsule opacification: A randomized clinical trial

Aim: To determine whether square-edge polymethyl methacrylate (PMMA) intraocular lens (IOL) is superior in preventing clinically significant posterior capsule opacification (PCO) and better visual outcome when compared with round-edge PMMA IOL in manual small-incision cataract surgery (MSICS). Settings and Design: Tertiary care hospital-based randomized controlled clinical trial. Materials and Methods: A randomized clinical trial of 1 year in which 128 patients were randomized into two groups to receive round-edge IOLs (Group A) or square-edge IOLs (Group B) after MSICS and followed up for 10 months; during follow-up, the best corrected visual acuity, grades, and type of PCO were documented. Statistical Analysis Used: Data analysis was done using chi-square test. Results: Out of 128 patients, the incidence of PCO was 83.6%, out of which 85.9% were in Group A and 81.2% were in Group B. Visual outcome was better in Group B, which was statistically significant (0.003). The fibrous type of PCO was the commonest type seen in the study irrespective of the group. There was less incidence of PCO in capsulorrhexis (with relieving incisions) and complete cortical cleanup cases. Difference in neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser capsulotomy rates were not statistically significant between the two groups (P = 0.784). Conclusions: This study showed that square edge PMMA IOLs had less clinically significant PCO rates and better visual outcome when compared to round-edge PMMA IOLs.

Square-edge intraocular lenses and epithelial lens cell proliferation: implications on posterior capsule opacification in an in vitro model.

BackgroundTo evaluate lens epithelial cell (LEC) proliferation with two different designs (one-piece or three-piece) of hydrophobic acrylic IOLs with 360° square optic edge using an in vitro culture model of posterior capsule opacification (PCO).MethodsThis experimental study was conducted at the Department of NEUROFARBA, Section of Pharmacology, University of Florence, Italy. Human LECs were seeded and cultured in transwell cell culture inserts coated with a type-IV collagen membrane on which an IOL (one-piece Tecnis-1 or three-piece AR40E, Abbott Medical Optics Inc.) had been previously placed. As control, cells were plated on the insert membrane without an IOL. At day six (cells confluent in controls) IOLs were removed and cell counting, viability and cell density under and outside the IOLs were evaluated.ResultsNo statistically significant difference in the number of cells (p > 0.05) between inserts with the one-piece and three-piece IOLs was found. Cell density in the area under each IOL was significantly lower than in the area outside of it (p < 0.05), or in the control insert. (p < 0.05). Cell density under the single-piece IOL was not significantly different from that under the three-piece IOL (p > 0.05).ConclusionsA 360° sharp-edge played a crucial role in avoiding LEC migration under the IOL and preventing the formation of PCO after cataract surgery. Long term clinical evaluation is necessary to estimate functional results.

Subjective complaints after cataract surgery: common causes and management strategies.

To describe the common causes of, and management strategies for, nonrefractive subjective visual complaints after cataract surgery. Over the past decade, clinical observations and ray-tracing models have greatly increased our understanding of positive and negative dysphotopsias after cataract surgery. The primary factor behind positive dysphotopsias is the use of high refractive index square-edge intraocular lenses (IOLs). Primary and secondary factors that underlie negative dysphotopsias are now better characterized, which has led to successful interventions including IOL exchange and Nd:YAG laser anterior capsulotomy. Positive and negative dysphotopsias occur after implantation of monofocal IOLs, and can rarely be disabling to patients. Visual complaints after multifocal IOL implantation are more common than after monofocal IOL implantation, but still rarely require significant intervention. A better understanding of the risk factors and optical causes of dysphotopsias will allow for IOL design and patient selection that maximize satisfaction after cataract surgery.

Scanning electron microscopic characteristics of commercially available 1- and 3-piece intraocular lenses

To evaluate commercially available 1- and 3-piece intraocular lenses (IOLs) with scanning electron microscopy (SEM). Department of Ophthalmology and Electron Microscopy Center, University Hospital Jena, Jena, Germany. Experimental study. Seven +23.0 diopter IOLs of different design and material and from different manufacturers were chosen for a detailed assessment. Scanning electron microscopy was used at standardized magnifications to assess typical IOL characteristics. The particular focus was the optic edge, the optic surface, the haptic–optic junction, and the haptic. All square-edged IOLs had a curvature radius of less than 10 μm, while the mean optic edge thickness ranged between 216 μm and 382 μm. A 360-degree square-edged boundary was present in all 3-piece IOLs and in a single 1-piece model. Relevant production remnants on the optic edge were observed in 1 case. Regarding the haptic, 3-piece IOLs had uniformly shaped fibers with a mean thickness of 177 μm ± 51 (SD) (range 116 to 220 μm). Chemical adhesives were used to attach the haptic in 1 case, where alterations of the IOL material were observed. In another case, the haptic fiber was press-fitted into the optic, which resulted in bulging of the optic profile. Inspection of surface characteristics showed wavelike patterns in 2 IOLs. Taking clinical relevance into account, all IOLs were of high manufacturing quality. Certain attention was paid in creating a sharp optic edge. Surface irregularities of 2 IOLs were attributed to the manufacturing technique. Methods for implementing the haptic–optic junction were diverse.

Pathology of 157 human cadaver eyes with round-edged or modern square-edged silicone intraocular lenses: Analyses of capsule bag opacification

To assess the degree of capsular bag opacification in human cadaver eyes with silicone intraocular lenses (IOLs), specifically comparing the differences between round-edged IOLs and modern square-edged IOLs. John A. Moran Eye Center, University of Utah, USA. Experimental study. The eyes were immersed in 10% formalin on enucleation. They had anterior segment scanning with a very-high-frequency ultrasound (Artemis). After the eyes were sectioned at the equator, gross examination of the anterior segment was performed from the posterior aspect to assess the degree of capsular bag opacification, coverage of the IOL edge by the anterior capsule, and IOL fixation. Selected eyes also had histopathologic examination. Eighty-seven eyes with a 3-piece round-edged IOL, 43 with a 3-piece square-edged IOL, 26 with a 1-piece plate IOL, and 1 with an accommodating IOL design were included in the analyses of capsular bag opacification. Comparison between 3-piece round-edged IOLs and square-edged IOLs showed statistically significant differences in central posterior capsule opacification (PCO) (P=.0001687) and peripheral PCO (P<.0001). In eyes with square-edged IOLs, PCO had a tendency to start in areas without capsulorhexis coverage of the optic. Twenty-one of 26 eyes with a silicone plate IOL had a neodymium:YAG posterior capsulotomy for dense PCO. This first study using pseudophakic human cadaver eyes that includes a significant number of modern 3-piece silicone IOLs with square optic edges confirmed the role of this design in the prevention of PCO. No author has a financial or proprietary interest in any material or method mentioned.

Comparison of the outcome of implantation of hydrophobic acrylic versus silicone intraocular lenses in pediatric cataract: prospective randomized study

Objective: To compare the postoperative performance of hydrophobic acrylic and silicone square-edge intraocular lenses in pediatric cataract. Design: Prospective randomized study. Participants: Forty-one eyes of 41 children (age 1 month to 8 years) with congenital or developmental cataract. Methods: Children were randomly divided into 2 groups. All participants underwent phacoaspiration, primary posterior capsulotomy, and anterior vitrectomy. Group A ( n = 21) eyes were implanted with acrylic hydrophobic AcrySof SA60AT intraocular lenses (IOLs), and those of Group B ( n = 20) were implanted with silicone Tecnis Z9000 IOLs. The children were evaluated for anterior chamber reaction, IOL position, posterior capsular opacifica-tion (PCO), intraocular pressure, best-corrected visual acuity (BCVA), corneal status, and refractive errors. Results: Postoperatively, 2 eyes in each group had significant anterior chamber reaction with fibrin membrane formation. IOLs were in the capsular bag in all but 1 eye in both groups. Seven eyes in the acrylic group and 6 eyes in the silicone group achieved visual acuity of 20/40 or better. None of the eyes showed glaucoma. BCVA at 1 year was similar in both groups. In the acrylic hydrophobic group, 14 eyes needed hypermetropic correction and 7 eyes were myopic, and in the silicone group 10 eyes had myopia and 10 eyes had hypermetropia at 1 year postoperatively. PCO at 1 yearfollow-up was more common in eyes implanted with acrylic hydrophobic IOLs (5 eyes) than silicone IOLs (2 eyes). Conclusions: Both square-edge hydrophobic acrylic and silicone IOLs were found to be compatible and safe for use in pediatric cataract surgery with similar visual axis clarity and postoperative outcome.

Incidence of Nd:YAG laser capsulotomies after cataract surgery: comparison of 3 square-edged lenses of different composition

Objective: To compare the incidence of Nd:YAG laser treatment following 3 square-edged intraocular lenses (IOLs) of different composition implanted during cataract surgery. Design: Patient chart analysis. Participants: Patients aged 50-85 years and given a hydrophobic acrylic IOL (either SA60AT or AR40E) or hydro-philic acrylic IOL (XL-Stabi) were included. Analysis was conducted of 767 eyes treated with SA60AT ( n = 250), AR40E ( n = 254), or XL-Stabi ( n = 263). Methods: This retrospective study involved patients who had undergone cataract surgery between 2001 and 2002. Ophthalmology centres were accepted into the study if they used at least 2 of the IOLs being investigated. The medical files of patients fulfilling the inclusion criteria were listed, and eligible cases were selected randomly. Patients’ characteristics were obtained from their medical files. Data on postsurgical complications and Nd:YAG laser treatment over 3 years were also extracted. Follow-up data were obtained from the medical files and the patients’ ophthalmologists. Time to Nd:YAG laser treatment was analysed using Kaplan-Meier survival curves adjusted with a Cox model. Results: After 3 years’ follow-up the proportions of patients who had not received Nd:YAG laser treatment were 87.0% with SA60AT, 76.6% with AR40E, and 54.6% with XL-Stabi ( p < 0.001). Cox’s model adjusted for centre effects and the presence of diabetes estimated risk ratios of 2.8 for AR40E ( p < 0.0005) and 5.1 for XL-Stabi ( p < 0.0001), compared with the reference lens SA60AT. Conclusions: Of the 3 square-edged lenses studied, the SA60AT was associated with a lower incidence of Nd:YAG laser treatment than either AR40E or XL-Stabi.

Nd:YAG laser capsulotomy rates following implantation of square-edged intraocular lenses: polymethyl methacrylate versus silicone versus acrylic

Objective: To study the influence of square-edged intraocular lenses (lOLs) on the development of posterior capsule opacification (PCO) and the requirement for laser capsulotomy. Design: Retrospective study. Participants: Three hundred seventy-seven eyes of 377 patients were included. Methods: All these patients underwent phacoemulsification and implantation of square polymethyl methacrylate (PMMA) (Aurolab), silicone (Tecnis Z9000), acrylic hydrophobic (AcrySof MA60AC and Sensar Optiedge), or acrylic hydrophilic (Akreos Adapt) lOLs with a minimum of 2 years’ follow-up. Only those cases in which Nd:YAG laser capsulotomy had been performed for visually significant PCO were evaluated. Results: Three hundred seventy-seven eyes of 377 patients were included in the study. Follow-up duration ranged from 24 to 54 (mean 40.27, SD 8.42) months. The incidence of PCO requiring Nd:YAG laser capsulotomy was found to be significantly less in the silicone lens group: 1.4% as compared with an incidence of 11.7% in the PMMA lens group (p = 0.018). In the square-edged acrylic group, visually significant PCO requiring Nd:YAG laser capsulotomy was observed in 3.6%, 4.8%, and 6.8% of eyes implanted with AcrySof MA60AC, Sensar Optiedge, and Akreos Adapt lOLs, respectively. In 5 of the 7 eyes (71.4%) exhibiting PCO in the PMMA group, the condition developed within the first 6 months. In the silicone and acrylic group, development of PCO was delayed. Conclusions: The rate of visually significant PCO as well as the need for Nd:YAG laser capsulotomy is influenced by IOL biomaterial in addition to square edge. It is significantly delayed with square-edged foldable acrylic and silicone lOLs compared with square-edged PMMA IOLs.

Edge profile of commercially available square-edged intraocular lenses

To analyze the sharpness of the posterior optic edge profile and edge thickness of intraocular lenses (IOLs) marketed with a square-edged profile. Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. Seventeen square-edged 20.0 diopter IOLs of different manufacture, design, and material were selected. After the environmental scanning electron microscopy technique was standardized, repeatability of the technique was tested. Posterior optic edges of all IOLs were scanned at a magnification of x 500. Local radii of curvature of the posterior optic edges were measured by purpose-designed software. Optic edge thickness was also measured from the electron micrographs. The repeatability of the scanning technique was excellent (+/-0.10 microm). The radius of curvature of posterior optic edges ranged from 7.6 to 23.1 microm. Hydrophilic acrylic IOLs (except the HumanOptics MC Microlens 611 MI-B and 1CU) had radii of curvatures more than 10.0 microm of the posterior optic edge compared with hydrophobic acrylic and silicone IOLs (<10.0 microm) except the Hoya AF-1 (19.9 microm). Alcon AcrySof single-piece (SN60WF), HumanOptics 1CU, and AMO Clariflex CLRFLXC IOLs had the thinnest optic edges in the hydrophobic, hydrophilic, and silicone groups, respectively. Commercially marketed square-edged IOLs differed in the sharpness of the posterior optic edge. Hydrophobic acrylic and silicone IOLs have sharper posterior optic square edge than most hydrophilic acrylic IOLs. This probably reflects difference in manufacturing techniques. Differences in posterior optic edge profile may explain variation in posterior capsule opacification performance with different IOLs and materials.

Preventing secondary cataract and anterior capsule contraction by modification of intraocular lenses

Advances in intraocular lens (IOL) design have led to the use of lenses with improved performance including tinting, asphericity, multifocality and accommodation. To maximize the visual performance of these IOLs, postoperative complications such as secondary cataracts and anterior capsule contraction must be prevented. Various types of secondary cataracts may occur, each associated with complex biological reactions. Different design configurations, including square-edge IOLs, have been used to prevent secondary cataracts and anterior capsule contraction, but these have not been successful in sufficiently eliminating these complications. We have found that surface modification of IOL surfaces chemically improves surface quality and is also useful in preventing secondary cataracts and anterior capsule contraction. The UV/ozone treatment that we used as a surface modification method is a simple and highly effective method with no safety issues regarding materials following treatment. The combination of square-edge design and surface modification may be able to completely eliminate these postoperative complications.

Evaluating and defining the sharpness of intraocular lenses: Microedge structure of commercially available square-edged hydrophobic lenses

To evaluate the microstructure of the edges of currently available square-edged hydrophobic intraocular lenses (IOLs) in terms of their deviation from an ideal square. Berlin Eye Research Institute, Berlin, Germany. Sixteen designs of hydrophobic acrylic or silicone IOLs were studied. For each design, a +20.0 diopter (D) IOL and a +0.0 D IOL (or the lowest available plus dioptric power) were evaluated. The IOL edge was imaged under high-magnification scanning electron microscopy using a standardized technique. The area above the lateral-posterior edge, representing the deviation from a perfect square, was measured in square microns using reference circles of 40 microm and 60 microm of radius and the AutoCAD LT 2000 system (Autodesk). The IOLs were compared with an experimental square-edged poly(methyl methacrylate) (PMMA) IOL (reference IOL) with an edge design that effectively stopped lens epithelial cell growth in culture in a preliminary study. Two round-edged silicone IOLs were used as controls. The hydrophobic IOLs used, labeled as square-edged IOLs, had an area of deviation from a perfect square ranging from 4.8 to 338.4 microm(2) (40 microm radius reference circle) and from 0.2 to 524.4 microm(2) (60 microm radius circle). The deviation area for the square-edged PMMA IOL was 34.0 microm(2) with a 40 microm radius circle and 37.5 microm(2) with a 60 microm radius circle. The respective values for the +20.0 D control silicone IOL were 729.3 microm(2) and 1525.3 microm(2) and for the +0.0 D control silicone IOL, 727.3 microm(2) and 1512.7 microm(2). Seven silicone IOLs of 5 designs had area values that were close to those of the reference square-edged PMMA IOL. Several differences in edge finishing between the IOLs analyzed were also observed. There was a large variation in the deviation area from a perfect square as well as in the edge finishing, not only between different IOL designs but also between different powers of the same design. Clinically, factors such as the shrink-wrapping of the IOL by the capsule may even out or modify the influence of these variations in terms of preventing posterior capsule opacification.

Effect of square-edged intraocular lenses on neodymium:YAG laser capsulotomy rates in the United States

To model the effect of the introduction of square-edged intraocular lenses (IOLs) in the United States on neodymium:YAG (Nd:YAG) laser capsulotomy rates and to compare the model with actual capsulotomy rates. Ophthalmology Department, St. Thomas' Hospital, London, United Kingdom, and Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. The actual numbers of cataract surgeries and Nd:YAG laser capsulotomies performed in the U.S. were obtained from Medicare claims data for 1993 to 2003. The percentage market share of square-edged IOLs was obtained, and numbers of square-edged and round-edged IOLs implanted were calculated. Predicted laser capsulotomy rates were modeled on published postmortem and clinical data and compared with actual capsulotomy rates. Between 1993 and 2003, the number of cataract surgeries and Nd:YAG laser capsulotomies reimbursed by Medicare rose by 67.4% and 18.9%, respectively. After the introduction of square-edged IOLs in 1995, the market share grew to 48.5% in 2003. The total number of Nd:YAG capsulotomies reimbursed by Medicare in 2003 exceeded the number of capsulotomies predicted by the model by at least 23.9%. The estimated cost generated by the discrepancy between predicted and actual laser capsulotomies in 2003 was at least US $30 million. After the introduction of square-edged IOLs, Nd:YAG laser capsulotomy rates decreased, but not by as much as predicted. The additional cost to the Medicare system was more than US $30 million higher than the model predicted.

Effect of intraocular lens edge profile on posterior capsule opacification after extracapsular cataract surgery in a developing country

To determine whether square-edged polymethyl methacrylate (PMMA) intraocular lenses (IOLs) reduce posterior capsule opacification (PCO) in the context of extracapsular cataract surgery in a developing country. A rural hospital in India. This was a prospective randomized double-masked fellow-eye controlled study. Over a 4-month period, 118 patients with normal eyes apart from age-related cataract were randomized to receive a square-edged or round-edged PMMA IOL in the first eye. The IOLs were identical apart from the edge profile. The fellow-eye had implantation of the alternative IOL within 1 month. Retroillumination images of the posterior capsule were taken using a dedicated camera system and analyzed to quantify the PCO area using POCO software 1 and 2 years postoperatively and the PCO area and severity using POCOman semiqualitative software at 2 years. Visual acuity was measured using a Gujarati logMAR chart. One hundred fifteen patients were available for examination at 1 year and 107 at 2 years. With POCO software, the PCO area was reduced in the square-edged IOL group at 1 year (median 30% versus 20%, P=.001) and at 2 years (median 45% versus 35%, P=.006). With POCOman, the PCO area and severity were reduced in the square-edged group at 2 years (median 41.5% versus 33.2%, P=.019 and 0.59 versus 0.46, P=.037, respectively). There was no significant difference in visual acuity between the 2 groups at 1 or 2 years. Sophisticated image analysis techniques can be used in developing countries to quantify PCO. Using extracapsular surgery, square-edged PMMA IOLs reduced the PCO area and severity compared with an identical round-edged IOL; however, the differences were not as marked as those reported with phacoemulsification. This may be due to the difficulty of performing a capsulorhexis that lies on the IOL surface in this situation. Nevertheless, square-edged IOLs offer a potential benefit for extracapsular surgery in the developing world.

Comparison of pseudophakic dysphotopsia with Akreos Adapt and SN60-AT intraocular lenses

To determine the relative incidence of unwanted light images with the AcrySof SN60-AT intraocular lens (IOL) (Alcon) and the Akreos Adapt (Bausch & Lomb) IOL. The Eye Clinic, Sir Charles Gairdner Hospital, Nedlands, Australia. In a prospective randomized study of 61 patients who had cataract surgery, the relative incidence of unwanted light images with 2 biconvex acrylic double square-edged IOLs, the SN60-AT and Akreos Adapt, was compared. Patients were followed at 1 week and for a minimum of 6 weeks. At both follow-ups, patients were asked to rate their experience of dysphotopic phenomenon according to a set of questionnaire criteria. The Mann-Whitney test was used to analyze the ordinal data. All 61 patients were interviewed at both stages of follow-up. The mean follow-up was 8 weeks +/- 2 (SD). At 1 week, there was significantly more dysphotopsia (positive and negative) with the SN60-AT IOL (37.5%) than with the Akreos Adapt IOL (24.1%) (P = .042). Significantly more patients with the SN60-AT IOL reported negative dysphotopsia at 1 week only. At 8 weeks, the incidence of positive and negative dysphotopsia declined to 31.3% and 20.7% in the SN60-AT group and Akreos Adapt group, respectively, and there was no longer a statistically significant difference between the 2 groups. More patients with the SN60-AT IOL than with the Akreos Adapt IOL reported dysphotopsia. One week postoperatively, the difference was significant. The difference was primarily a result of the higher incidence of negative dysphotopsia with the SN60-AT IOL. At 8 weeks, the incidence of all types of light phenomena was significantly lower in both groups.