Poly Methyl Methacrylate Intraocular Lens Research Articles

NEODYMIUM: YAG;

Objective: To evaluate the incidence of posterior capsule opacificationafter phacoemulsification, between acrylic and polymethylmethacrylate intraocular lenses, by comparing their YAG lasercapsulotomy rates. Design: It was a randomized clinical trial. Place and duration of study: Department ofOphthalmology, Military Hospital Rawalpindi, between March 2002-04. Patients and Methods: One hundred and fivepatients were randomized to receive either a foldable acrylic lens (fifty-two cases), or rigid polymethylmethacrylate lens(fifty-three cases) following phacoemulsification for cataracts. Postoperatively their visual acuities were recorded alongwith the presence of posterior capsular opacification. Laser capsulotomy was performed if the eyes had lost 2 or morelines of visual acuity. Results: The visual acuity loss at six months in the PMMA group was greater than that in theacrylic group (p< 0.001,Chi-square test).65% cases exhibiting PCO in the Polymethylmethacrylate group developedit within the first six months, whereas in the acrylic group the development of posterior capsular opacification was seeneighteen months after surgery in 60% cases. Nd: YAG laser capsulotomy was performed in 28% of cases in the PMMAgroup compared to 6% in the AcrySof group (p < 0.005). Conclusion: Acrylic intraocular lenses is associated with lessincidence of posterior capsular opacification and with a significantly reduced rate of YAG laser capsulotomy comparedwith Polymethylmethacrylate lenses.

Influence of intraocular lens material on the development of acute endophthalmitis after cataract surgery?

To investigate the causal relationship between acute postoperative endophthalmitis (POE) after cataract surgery and the biomaterial properties of the intraocular lens (IOLs) implanted. This retrospective cohort study included all patients who had undergone cataract surgery with IOL implantation at the Lyon Croix-Rousse University Hospital between 1st January 1994 and 31st December 2004. Details respecting the type of IOL implanted (material and manufacturer) were meticulously recorded. The number of patients presenting with POE within 6 weeks of cataract surgery was documented together with their medical characteristics. These data were then compared, and Fisher's exact test was used to establish the significance of any apparent associations. Eight of the 5837 eyes manifested acute POE (0.14%). Seven of these were composed of polymethylmethacrylate (PMMA) and one of heparinized PMMA. Patients with PMMA IOLs carried a higher risk of developing POE than did those implanted with either heparinized PMMA (P=0.001), hydrophilic acrylic, or hydrophobic acrylic IOLs (P=0.002). The incidence of acute POE after cataract surgery in our hospital is similar to that currently reported for other institutions in developed countries. Our results add further evidence that IOL material and type are factors contributing to the risk to develop an acute POE after cataract surgery, and that PMMA IOLs may be associated with an increased risk of POE.

Localized, Central Optic Snowflake Degeneration of a Polymethyl Methacrylate Intraocular Lens: Clinical Report With Pathological Correlation

Localized, Central Optic Snowflake Degeneration of a Polymethyl Methacrylate Intraocular Lens: Clinical Report With Pathological Correlation

Effect of ophthalmic Nd:YAG laser energy on intraocular lenses after posterior capsulotomy in normal dog eyes

To determine Nd:YAG laser energy requirements for posterior capsulotomy and intraocular lens (IOL) damage threshold for foldable acrylic IOLs as compared to traditional polymethylmethacrylate (PMMA). MATERIALS AND PROCEDURES: Four groups of five-six fresh canine cadaver eyes were used in this study. The groups included (1) unaltered eyes (2) aphakic eyes (3) eyes implanted with PMMA IOLs, and (4) eyes implanted with acrylic IOLs. Laser energy was delivered to the posterior capsule in grid fashion for 10 sites each of five levels of laser energy ranging from 0.5 mJ to 9 mJ. Number of successful capsulotomy sites was recorded based on slit-lamp observation. Sites of IOL damage were evaluated using scanning electron microscopy (SEM). Statistical analysis of number of capsulotomies and IOL defects per laser energy level was conducted among and between groups using anova with Tukey's HSD test. When comparing groups (a) including all energy levels (n = 25) and (b) by specific energy levels (n = 5), there was no significant difference (P < 0.05) in number of successful capsulotomy sites between IOL types. The 50% incidence threshold for successful capsulotomy was 2.74 mJ for acrylic IOLs and 2.64 mJ for PMMA IOLs. Energy-dependent damage to both types of IOL was detected for medium, high-medium, and high laser energy. Calculated 50% damage threshold was 4.9 mJ for acrylic IOL and 5.7 mJ for PMMA IOL. Damage to the IOL varied subjectively between IOL type, but there was no significant difference in number of defects caused, with the exception of high-medium energy. Both posterior lens capsules and IOLs were disrupted in an energy-dependent manner with minimal difference in number of capsulotomy sites or damage to the IOL between acrylic and PMMA IOLs. A therapeutic margin between capsulotomy threshold (2.6-2.7 mJ) and IOL damage threshold (4.9-5.7 mJ) was determined to reliably achieve capsulotomies with minimal IOL damage for both acrylic and PMMA IOLs in normal canine cadaver eyes.

Incidence and risk factors of Nd:YAG capsulotomy after phacoemulsification in non‐diabetic and diabetic patients

To estimate the cumulative incidence and identify the risk factors of posterior capsule opacification (PCO) that required Nd:YAG capsulotomy in non-diabetic and diabetic patients. Retrospective case-note review of 806 consecutive patients that underwent phacoemulsification and intraocular lens (IOL) implantation, 327 (40.6%) of whom were diabetic. The cumulative incidence of Nd:YAG capsulotomy were 10.6%, 14.8%, 21.2% and 28.6% in non-diabetic patients; and 9%, 9.4%, 15.3% and 5.3% in diabetic patients after 1, 2, 3 and 4 years, respectively. A multivariate Cox regression analysis showed that, over the follow-up period, diabetes mellitus was associated with a decreased risk of Nd:YAG capsulotomy (hazard ratio [HR]=0.69; 95% confidence interval [CI] 0.47-0.99; P=0.047), whereas age of 65 years or younger (HR=1.58; 95% CI 1.09-2.27; P=0.02), polymethylmethacrylate (PMMA) (HR=3.98; 95% CI 1.60-9.95; P=0.003) or plate-haptic silicone IOLs (HR=3.75; 95% CI 1.60-8.80; P=0.002) in comparison with three-piece silicone IOLs, postoperative inflammation (HR=2.62; 95% CI 1.56-4.42; P<0.001) and pars plana vitrectomy (HR=1.85; 95% CI 1.20-2.83; P=0.005) were associated with an increased risk. Subgroup analysis showed that in non-diabetic patients, male gender (HR=1.63; 95% CI 1.04-2.57; P=0.03) was an additional risk factor and in diabetic patients there was no significant association between diabetes type, duration or retinopathy grade and the risk of Nd:YAG capsulotomy. Although diabetes mellitus appears to be associated with a lower long-term incidence and a decreased risk of Nd:YAG capsulotomy, younger age, pars plana vitrectomy, postoperative inflammation, plate-haptic silicone and PMMA IOLs in addition to male gender in non-diabetic patients appear to be associated with a greater risk. Estimation of the incidence and risk factors of PCO should help in patient counselling and to design methods to reduce or prevent its development.

Aderência in vitro do Staphylococcus epidermidis e da Pseudomonas alcaligenes em lentes intra-oculares

To quantify and compare the in vitro adherence of Staphylococcus epidermidis and Pseudomonas alcaligenes to different intraocular lenses (IOLs). Fourteen intraocular lenses were used in the experiment. Four of polymethylmethacrylate (PMMA), four of silicone, four of hydrogel and two of acrylic. Eight intraocular lenses were placed in eight test tubes containing 4 ml of Pseudomonas alcaligenes suspension, and six intraocular lenses were placed in six test tubes containing 4 ml of Staphylococcus epidermidis suspension. The bacterial suspension used for adherence tests was 10(8) colony-forming units per milliliter (CFU/mL) which corresponds to 0.5 in the scale of McFarland. The lenses were incubated at 37 degrees for two hours. After this, intraocular lenses were removed from the test tubes and dried twice with the use of distilled and sterile water. The material was spread on blood-agar for cultivation at 35-37 degrees C and was evaluated every 24 hours up to 72 hours. In the samples where there was bacterial growth, the colonies were counted using the conventional laboratory methods. All assays were performed in duplicate. Adherence of Staphylococcus epidermidis to PMMA intraocular lenses was lower than to hydrogel and silicone intraocular lenses. Adherence of Pseudomonas alcaligenes to hydrogel intraocular lenses was lower than to PMMA, acrylic and silicone intraocular lenses. Results suggest that in vitro adherence of Staphylococcus epidermidis and Pseudomonas alcaligenes to intraocular lenses is influenced by type of material of the lens and by microorganism species. Bacterial adherence may play a role in the pathogenesis of some forms of endophthalmitis after cataract surgery. More in vitro and clinical studies are necessary to elucidate the mechanisms by which Staphylococcus epidermidis and Pseudomonas alcaligenes cause endophthalmitis.

Comparison of acrylic and polymethyl methacrylate lenses in a pediatric population

To compare the intra-patient incidence of posterior capsular opacification (PCO) and their post operative course, in children with bilateral cataract, following implantation of acrylic (Group 1) and polymethyl methacrylate (PMMA) (Group 2) intraocular lenses (IOLs). This was a prospective, interventional intra-patient case series. Twenty-five children with bilateral cataract, 5 years and older, underwent cataract surgery and implantation of an acrylic (AcrySof MA30BA, Alcon, Fortworth, TX) in one eye and PMMA (Indo Am IAB 203, Ocular Vision, Inc.) IOL in the other eye of each patient. They were followed up for an average of 11.1 +/- 9.5 months to assess the incidence of clinically significant PCO and occurrence of postoperative complications. Twenty-three children (46 eyes), were included in this study. Post-operatively, 22(95.6%) patients with acrylic IOLs and 20 (86.9%) patients with PMMA IOLs, either maintained or improved their vision. In the acrylic and PMMA IOL groups respectively, the incidence of clinically significant PCO was 21% (4) and 75% (12) ( P =0.002), with a median onset at 2.9 months and 0.7 months. Other complications included pupillary capture in 2 (8.7%) eyes and uveal prolapse in 1 (4.3%) eye in the acrylic group and increased uveal inflammation in 6 (26.1%) eyes and presumed noninfectious endophthalmitis in 2 (8.7%) eyes in the PMMA group. Incidence of PCO and post operative uveal inflammation is significantly less with acrylic lenses and were safe to use in pediatric eyes.

Post‐operative endophthalmitis and IOL material

Editor, We wish to thank Drs Kodjikian, Burillon and Freney for their valuable comments regarding intraocular lens (IOL) material and its relation to postoperative endophthalmitis (POE) described in the paper ‘Endophthalmitis following cataract surgery in Sweden. The 1998 National Prospective Survey’ (Montan et al. 2002a). One of the findings of this study was that acrylic lenses were significantly less associated with POE than polymethylmethacrylate (PMMA) and hydrogel lenses. In contrast to what the writers of the letter claim, we did not conclude that acrylic is a less permissive material for POE. On the contrary, the conclusion of our paper states that our data in this regard ‘should be interpreted with much caution’. The reason for this caution is obvious: detailed data regarding a number of parameters with possible relevance for POE were simply not available through the register form for the control group. Kodjikian et al. are thus perfectly right in their criticism regarding the lack of information on a number of factors that might alter the risk of postoperative infection, such as the exact design and property of the IOL (not only the optic material), the presence of any putative innate propensity for developing infection in the operated patient, and, factors we perceive as highly essential, the prophylaxis regime and perioperative complications. These shortcomings were also thoroughly addressed in the discussion section of the paper. We nevertheless think it is interesting to address the issue of IOLs in relation to POE in this crude form, as previous studies have identified increased associations between certain IOL materials and POE (Menikoff et al. 1991; Bainbridge et al. 1998; Montan et al. 1998). We have continued to publish data from the Swedish National Cataract Register (NCR) (Wejde et al. 2005). We believe that if there were important differences in the adhesiveness of bacteria to various lens materials, divergent patterns of POE frequencies would be found in a consistent manner. In such an event it would be feasible to perform a posthoc investigation in order to pinpoint the exact lens design and to screen for various risk factors in the disease group. We did not feel that such an assessment was warranted in the present paper because our forthcoming studies will be based on a far more extensive material. All the lens types cited in our first paper in Acta were in fact compared with one another and a consequent lowering of the p-value was performed, as is clearly stated in the methods section. The only statistically significant results found were between acrylic lenses and the two other materials mentioned above. Therefore, only the comparisons between acrylic lenses and these other types were presented, but the actual POE frequencies for all IOL types were reported in a table and could easily be calculated with a statistical program by anyone interested. Finally, Kodjikian et al. wish to have our comments on a previously reported finding that heparinized PMMA IOLs may protect against POE, which is at odds with the present results. This may be explained by the fact that the previous results were obtained in an era with a higher POE rate than is found presently in our country (0.25% versus the present incidence of 0.06–0.1%) (Montan et al. 2002b). In addition, the unfoldable heparinized PMMA IOL was not used as a back-up lens at the time, which seems to be the case presently, in that surgeons today use a rigid heparinized lens in the event of a capsular break, a perioperative complication which in itself may predispose to infection. The tendency to develop POE is certainly multifactorial and only large scale, prospective studies with meticulous protocols will be able to establish whether any IOL is more protective than others against POE. In the meantime, we believe that the ongoing POE registration through the NCR may provide some useful information in this respect.

Long-term Effect of Sharp Optic Edges of a Polymethyl Methacrylate Intraocular Lens on Posterior Capsule Opacification: A Randomized Trial

To compare the posterior capsule opacification (PCO) inhibiting effect of a 3-piece polymethyl methacrylate (PMMA) intraocular lens (IOL) with a sharp optic edge design with that of the round-edged version of the same IOL during a 5-year period.Randomized patient- and examiner-masked clinical trial with intraindividual comparison.Thirty-two patients with bilateral age-related cataract (64 eyes).Each study patient had phacoemulsification cataract surgery in both eyes and received a sharp optic edge PMMA IOL in one eye and a round optic edge PMMA IOL in the fellow eye (both by Dr Schmidt in Germany). Follow-up examinations were at 1 week, 1 month, 1 year, 3 years, and 5 years. Digital retroillumination images were taken from each eye. The amount of posterior capsule opacification was assessed objectively by means of automated image analysis software (Automated Quantification of After-Cataract) at 1 year, 3 years, and 5 years after surgery.Posterior capsule opacification score: 0-10.The sharp optic edge IOL showed significantly less regeneratory and fibrotic PCO at 1 year, 3 years, and 5 years after surgery. The mean AQUA PCO score was 5.12 for the round-edge and 2.49 for the sharp-edge IOL (scale, 0-10; P<0.001) at 5 years. The mean difference among patients for the PCO score in the eye implanted with the sharp optic edge versus the score in the eye with the round optic edge was 2.83 at 5 years (95% confidence interval, 1.66-4.00). Due to the large number of neodymium:yttrium-aluminum-garnet laser capsulotomies that were performed (12 in the round-edge group and 4 in the sharp-edge group), there was no significant difference in visual acuity between both groups at any time point.Compared with the round-edge version, the sharp optic edge design of a 3-piece PMMA IOL led to significantly less PCO at 1 year, 3 years, and 5 years after surgery. However, the sharp optic edge did not lead to complete PCO prevention during this follow-up period. This finding has implications for the design of PMMA IOLs used for cataract surgery, especially in the developing world.

Differential responses of human lens epithelial cells to intraocular lenses in vitro: hydrophobic acrylic versus PMMA or silicone discs

The purpose of this study was to determine the influence of different materials of intraocular lenses (IOLs) on human lens epithelial cell behavior, including adhesion, migration, proliferation, apoptosis, and epithelial-mesenchymal transdifferentiation (EMT) in vitro. Human lens epithelial cells (SRA 01/04) were grown on hydrophobic acrylic (Acrysof), polymethylmethacrylate (PMMA), and silicone IOLs. Cellular adhesion, migration, proliferation, and apoptotic assays were performed to assess cell behavior. The expression of EMT markers (fibronectin and type I collagen) produced by cells on IOLs was determined by immunoblotting and immunocytochemistry. Human lens epithelial cells exhibited preferred adhesion and reduced apoptosis when cultured on acrylic IOLs, in comparison to PMMA and silicone IOLs. Cells grown on acrylic lenses formed a confluent epithelial monolayer. Migration of lens epithelial cells under the acrylic lens was substantially blocked in an in vitro assay. In contrast, cells grown on PMMA and silicone lenses displayed a spindle-shaped, myofibroblast-like morphology, increased apoptosis, reduced adhesion, and enhanced production of EMT proteins such as fibronectin and type I collagen. The migration of lens epithelial cells under PMMA and silicone IOLs was substantial in the in vitro assay. This report demonstrates that hydrophobic acrylic lenses are more capsular biocompatible than PMMA and silicone lenses. The in vitro assays are reliable measurements for evaluating the responses of human lens epithelial cells to different IOL materials, and could advance our understanding of the preferential capsular opacification conferred by different IOL materials.

YAG curios #2: Nd:YAG laser treatment following suction posterior capsulorhexis

Suction posterior capsulorhexis (SPC) is a relatively new technique for creating a posterior capsulorhexis. We present a case series of seven patients who required Nd:YAG laser treatment 27 months after SPC. No patient had pre-existing risk factors for increased postoperative inflammation and all received a one-piece polymethylmethacrylate intraocular lens placed in-the-bag. Although it reduces the need for Nd:YAG laser treatment, SPC, like the more usual forceps posterior capsulorhexis, does not completely eliminate it.

Chemoattraction of Inflammatory Cells by Various Intraocular Lens Materials

Purpose: To compare the chemotactic activity induced by polymethyl methacrylate (PMMA), acrylic, and silicone intraocular lens (IOL) materials, regardless of the surgical and host factors. Methods: The chemotactic effect of five different IOLs was studied using a modified multi-well Boyden chamber. Two different non-coated PMMA IOLs, a heparin-coated PMMA IOL, an acrylic IOL, and a silicone IOL were assessed. Each mean migration distance of the IOLs was compared with the others using Student's t test. Results: All IOLs induced some amount of leukocyte chemotaxis. There was no statistically significant difference between the chemotactic activity of PMMA IOLs. However, chemotactic activity was significantly higher in acrylic (p < 0.05) and silicone (p < 0.05) IOLs compared to one of the PMMA lenses. Conclusions: This limited study has proven that chemotaxis assay is a useful tool to assess the biocompatibility of IOLs. The IOL material itself might attract inflammatory cells to its surface in the absence of surgical and host factors. As PMMA IOLs do not cause an increase in inflammatory reaction, they may be considered safe to use. Further improvement in chemical composition and surface characteristics of IOLs should reduce the inflammatory reaction and increase the biocompatibility and safety of IOLs.

Cost-Effectiveness Analysis of PMMA, Silicone, or Acrylic Intra-Ocular Lenses in Cataract Surgery in Four European Countries

Purpose: To compare the cost-effectiveness of different intra-ocular lens (IOL) materials (Hydrophobic acrylic, Polymethylmethacrylate (PMMA), Hydrophilic acrylic and Silicone) implanted after cataract surgery with reference to Nd:YAG laser capsulotomy and Nd:YAG-related complications in four European countries (France, Italy, Germany and Spain). Setting: A retrospective review of 1,525 patients (eyes), aged 50 to 80 years, operated with phacoemulsification for cataract in 1996 or 1997 in 16 surgical centres (4 per country). Methods: The study was conducted using a cost-effectiveness approach. Medical charts were reviewed to collect retrospective information during the 3-year period following cataract surgery in order to identify patients who underwent Nd:YAG laser capsulotomy post-operatively. Clinical data were combined with unit costs assessed by experts for Nd:YAG laser capsulotomy and their complications. A cost-effectiveness ratio (cost per patient without Nd:YAG laser capsulotomy intervention) was estimated in relation to each IOL material used in each of the four European countries. Results: Hydrophobic acrylic, specifically Acrysof ®, was the most cost-effective IOL material in all the countries except Germany where it was second. PMMA had the best ratio in Germany, was second in Spain and only third in Italy and France. Silicone was second in France and ranked third in the other countries, while hydrophilic acrylic had the worst ratio overall in all countries. Conclusions: Cost-effectiveness ratios of hydrophobic acrylic (Acrysof ®) were better than those of other types of IOL materials used in most of the countries. Sensitivity analyses were performed to vary the base case analysis to demonstrate the economic importance of the assumptions. In all cases, hydrophobic acrylic IOL material was shown to be a highly cost-effective option.

Contaminação bacteriana da câmara anterior pós-facoemulsificação com implante de lente intra-ocular de polimetilmetacrilato ou silicone

PURPOSE: To evaluate bacterial anterior chamber contamination following uncomplicated phacoemulsification with differents sizes of incisions. METHODS: Prospective randomized study, 80 eyes, 80 patients divided into two groups, were submitted to phacoemulsification with topical anaesthesia. In group A, with 40 patients, surgery was perfomed with 3.0 mm incision and silicone intraocular lens implant with injector. In group B the surgery was done with 5.8 mm incision and polymethylmethacrylate intraocular lens implant with forceps. Anterior chamber aspirate was taken for culture upon completion of surgery in each case. RESULTS: Anterior chamber cultures were positive in 2.5% of the cases in group A, and 5.0% in group B (chi-square test = 0.380, p>0.05), frequencies of contamination were not significantly different. CONCLUSION: Intraocular lens implant through a smaller incision did not decrease anterior chamber contamination in phacoemulsification.

Foldable acrylic versus rigid polymethylmethacrylate intraocular lens in combined phacoemulsification and trabeculectomy

Background: Combined trabeculectomy and phacoemulsification is a widely accepted option in treating patients with glaucoma who also have cataracts. Implantation of a foldable intraocular lens (IOL) in cataract surgery has several theoretical advantages. We performed a study to determine the results of combined phacoemulsification and trabeculectomy with mitomycin C and implantation of either a foldable acrylic or rigid polymethyl methacrylate (PMMA) IOL.Methods: Review of the charts of 58 consecutive patients (60 eyes) who underwent combined phacotrabeculectomy for concomitant cataract and glaucoma at a university-affiliated hospital in Montreal between September 2001 and December 2002. Forty-one eyes received a foldable acrylic lens (3.2-mm-wide incision), and 19 eyes received a rigid PMMA lens (5.2-mm-wide incision). Outcome measures included visual acuity, intraocular pressure (IOP) and postoperative complications. The results in the two groups were compared.Results: There were no differences in baseline characteristics between the two groups. Earlier recovery of visual acuity was noted in the foldable IOL group than in the rigid IOL group (p = 0.013 for the difference at day 7). IOP control was similar in the two groups, as was the incidence of IOP spikes in the early postoperative period.Interpretation: The results suggest that combined phacotrabeculectomy with mitomycin C using a foldable acrylic IOL allows for good postoperative IOP control and earlier visual recovery than the same procedure with insertion of a rigid PMMA lens.

Evaluation of a human capsular bag model for secondary cataract determination after intraocular lens implantation

To investigate the effect of different intraocular lenses (IOLs) on lens epithelial cells (LECs) and on human capsular bags in vitro and to evaluate the transferability of this model to clinical situations. Sham cataract surgery, including IOL-into-the-bag implantation, was performed on 38 donor eyes after removal of the cornea. The capsular bag including the IOL was removed, pinned on a culture dish, covered with medium, and incubated. Two different IOLs were compared per pair of donor eyes. In each pair of donor eyes, the two different IOLs to be compared were implanted individually into capsular bags. The time required for complete coverage of the posterior capsule by a confluent monolayer of LECs was documented. The following IOLs were compared: three-piece acrylic IOLs of different sizes and single-piece polymethylmethacrylate (PMMA) versus acrylic IOLs. A complete monolayer of LECs on the posterior capsule was observed to form at times varying from 8 days (PMMA IOLs) to more than 60 days (three-piece hydrophobic acrylic IOLs). A significant difference between PMMA IOLs and hydrophobic acrylic IOLs was found. The human capsular bag model employed allows short-term evaluation of secondary cataract formation for different IOLs. This model's correlation with clinical results is good.

A 1-year study on carbon, titanium surface-modified intraocular lens in rabbit eyes

To evaluate biocompatibility of Carbon (C) and Titanum (T) surface modified Polymethyl-methacrylate (PMMA) Intraocular Lens (IOLs) in pseudophakic rabbit model. Extracapsule Cataract Extraction (ECCE) and IOLs implantation were performed in Japanese albino rabbit eyes. The white cell concentration from the aqueous humor in the eyes was counted within 3 months post operation. The inflammatory cells in the eyes were noted and graded by slit lamp using a semiquantitive scale up to 1-year post operation. The rabbit eyes were inspected under light microscopy, where pathology of the eyes was caracterized. The white cell concentration in the aqueous humor was significantly attenuated in C and T IOL-implanted eyes compared with PMMA IOL-implanted eyes 1 week post operation. The exudate levels in the anterior ocular chamber and the posterior synechias were significant lower in T IOL-implanted eyes than in PMMA IOL-implanted eyes 1 week and 2 weeks after surgery. The exudate levels in the anterior chambers and the posterior synechias were not significantly different in C IOL-implanted versus PMMA IOL-implanted eyes. This in vivo study provides evidence of effectiveness of Carbon and Titanium IOLs in improving the biocompatibility of PMMA IOLs.

Bendazac Lysine Inhibition of Human Lens Epithelial Cell Adhesion to Polymethylmethacrylate Intraocular Lenses

The aim of the present work was to evaluate the effect of bendazac lysine on the human lens epithelial cell line HLE-B3 adhesion to polymethylmethacrylate (PMMA) intraocular lenses (IOLs). After adherence to IOLs, cells were incubated in the presence of the drug for 24 h. The number of cells contained in a 6-mm² area was then counted with an inverted phase microscope and adherent cells were distinguished from detached floating cells by focusing through the medium. Results obtained show that bendazac is able to induce a linear dose-dependent inhibition of HLE-B3 adhesiveness to PMMA IOLs. In particular, treatment with bendazac 33, 100 and 300 µM resulted in a 15, 32 and 54% inhibition, respectively. Statistical analysis shows that this effect is significant at 100 µM (p < 0.05) and 300 µM (p < 0.01). The analysis of the effects of bendazac on the viability and on the proliferative capacity of HLE-B3 cells did not show any drug-related toxicity up to the concentration of 400 µM. The present study demonstrates that bendazac lysine is able to inhibit adhesion of lens epithelial cells to PMMA IOLs and suggests the potential beneficial use of this drug in preventing secondary cataract development.

Clinical Evaluation of Posterior Capsule Opacification in Eyes With Different Small-Incision Intraocular Lenses

To present a new method to quantify posterior capsular opacity with an anterior eye segment image analyzer (EAS 1000, NIDEK). This study was comprised of patients who underwent phacoemulsification intraocular lens (IOL) implantation. Three types of IOLS, acrylic, silicone, and polymethylmethacrylate (PMMA) were allocated to 30 eyes and clinically evaluated. Patients were observed for 3 years postoperatively using an anterior eye segment image analyzer (EAS1000). Opacity was determined by calculating the area of opacity from a retroillumination image. In the retroillumination mode of analysis, the measurement was limited to a 4-mm-diameter region of the pupillary zone to eliminate the influence of anterior capsular opacity. For color map analysis, the threshold level was expressed as the color tone of 0-255 CCT (computer compatible tape). The glare disability was measured to evaluate the three types of IOLs. The color map analysis revealed a time-related increase in the opacity level of patients receiving the PMMA IOL implant. Three years after surgery, the levels were significantly higher in the PMMA group (P < 0.01) compared to the acryl and silicone groups: acryl (17.5 +/- 3.8), silicone (18.0 +/- 6.2%), and PMMA 36.5 +/- 32.9%. Quantitative evaluation using an anterior eye segment image analyzer is effective for observing the degree of posterior capsule opacification. The color map analysis using an anterior eye segment image correlated with the visual function revealed that the time-related increase in the opacity level was significant during the third year in patients receiving PMMA IOL implantation.

Snowflake degeneration of polymethyl methacrylate posterior chamber intraocular lens optic material: A newly described clinical condition caused by unexpected late opacification of polymethyl methacrylate

Objective To report 25 cases of gradual, but sometimes progressive, late-postoperative degeneration of polymethyl methacrylate (PMMA) optics of posterior chamber (PC) intraocular lens (IOL) implants, often resulting in a clinically significant visual decrease long after the implantation, sometimes to a severity that required IOL explantation/exchange. Design Analysis of explanted PC IOLs, clinical histories, and photographs. Participants We analyzed 25 case histories/photographs and/or explants from 18 patients implanted in the 1980s to mid-1990s with three-piece PC IOLs with PMMA optics and with polypropylene or PMMA haptics. The IOL optic from each case had characteristic snowflake or crystalline opacifications. This condition occurred with more than one manufacturer and in some cases was restricted to certain lot numbers. Methods The explanted IOLs (n = 10) were studied by gross inspection and by light and scanning electron microscopy, as well as confocal and energy dispersive spectroscopy. Main outcome measures The snowflake lesions were noted within the IOL optics. The nature of these lesions was investigated. Results Assimilation of clinical information with pathologic and morphologic profiles of all cases suggested that the snowflake opacification was a small spherical lesion surrounded by an outer pseudocapsule composed of compressed, degenerated PMMA, with a central core containing convoluted fragments of PMMA. The lesions were classified into four clinical and pathologic grades according to their density and severity. Conclusions This is the first clinicopathologic correlative report on this complication. We postulate that manufacturing variations in some IOL models fabricated in the 1980s and early 1990s are responsible. The snowflake lesions seem to represent a destruction of the PMMA material. The cluster of lesions in implanted lenses manufactured by Surgidev was less progressive than some other models, including lenses made by IOPTEX Research Corporation. This identification of a condition previously unreported is important to alert clinicians regarding these perplexing lesions that may otherwise be considered idiopathic, with no obvious clinical hint as to their origin. The prevalence noted thus far is still too low to in any way suggest that this condition would occur in 100% of PMMA IOLs from these manufacturers. However, these late-occurring lesions, present in lens models that were implanted in hundreds of thousands of patients in the last decade or so, could have constituted a true epidemic, except that many of the patients are now deceased.