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

PURPOSE: To evaluate the safety and performance of a foldable silicone intraocular lens (IOL) in small incision phacoemulsification surgery. SETTING: Vaasa Central Hospital, Vaasa, Finland. METHODS: Phacoemulsification with primary implantation of a posterior chamber IOL was performed in 50 patients. All eyes were implanted with a CeeOn IOL (model 920, Pharmacia & Upjohn) with a silicone optic and poly(methyl methacrylate) haptics. The ease of folding, implanting, and unfolding the IOL in the bag were recorded. Visual acuity, postoperative complications, optic decentration, and optic tilt were measured at 5 postoperative visits. The IOLs were evaluated for haze and discoloration and the IOL surface, for inflammatory or pigment deposits. Follow-up was 12 months. RESULTS: In 44 of 50 cases, folding the IOL was easy, and in 46 of 50, unfolding the IOL was controlled. The mean follow-up was 11.45 months +/- 0.52 (SD). No postoperative complications occurred, and 96% of patients achieved a best corrected visual acuity (BCVA) of 0.5 or better and 56%, a BCVA of 1.0 or better. The IOL decentration was less than 0.25 mm in 89% of cases, and there was no optic tilt. The neodymium:YAG laser capsulotomy rate was 11%. CONCLUSION: Good visual outcome and excellent centration were achieved with the CeeOn model 920 IOL. It is therefore suitable for small incision cataract surgery. Because of the IOL's smooth, polished surface, the choice of instruments for folding and implantation is important.     

Straight-entrance, sclerocorneal valve incision with horizontal sutures for poly(methyl methacrylate) intraocular lenses

Self-sealing sclerocorneal tunnel incisions with an external frown entry are widely used for implantation of poly(methyl methacrylate) intraocular lenses. Although safe and effective, these incisions have certain drawbacks. We developed a wound construction in which a straight external incision is used in conjunction with a tension-free, infinity-type suture. Out of 100 consecutive cases, only two did not seal satisfactorily at the conclusion of surgery but were tight upon placement of re-enforcing sutures. Postoperatively, the valve remained tight in all cases; there were no cases of hypotony, filtering bleb, flat chamber, or pupil capture or endophthalmitis indicating transient leakage. Flattening in the vertical and steepening in the horizontal meridian were minor and nonprogressive.     

In vitro evaluation of inflammatory cell response after CF4 plasma surface modification of poly(methyl methacrylate) intraocular lenses

Nasal intermittent positive pressure ventilation (NIPPV) provides effective ventilatory support in patients with nocturnal hypoventilation. Nasal pressure support ventilation (NPSV), which only provides ventilation in response to patient triggering, may also be effective, simpler, and cheaper, but has not been evaluated. NIPPV and NPSV were compared in 12 patients with nocturnal hypoventilation, requiring domiciliary ventilatory support. The patients were studied on three consecutive nights, in random order: a control night without ventilation and a night on each mode of ventilatory support using the bilevel positive airway pressure (BiPAP) ventilator. Both NIPPV and NPSV significantly increased mean arterial oxygen saturation (SaO2) compared to the control night (NIPPV mean increase 4.1%; 95% confidence interval (CI) 2.2 to 6.1, NPSV 4.4%; CI 2.1 to 6.6) with no significant difference between the two modes. The percentage of the study night spent below 90% SaO2 was significantly reduced by both ventilator modes compared to the control night (median reduction on NIPPV 37%; CI -54 to -10, reduction on NPSV 31%; CI -53 to -9, with no significant difference between NPSV and NIPPV. NPSV was as effective as NIPPV in patients with nocturnal hypoventilation, which suggests that these patients are able to trigger the ventilator adequately. The lower cost of NPSV will make it accessible to more patients with chronic lung disease.     

In vitro studies of poly(methyl methacrylate) adjuvants

Poly(methyl methacrylate) adjuvants, prepared by polymerizing monomeric methyl methacrylate in the presence of influenza virions or by addition of the virions to previously polymerized poly(methyl methacrylate) particles, were studied by means of the hemagglutination test, antibody binding, and electron microscopy. The results indicated that the virions were coated partly when the polymerization was carried out in the presence of the virus, whereas the virions were probably adsorbed when added to polymerized particles.     

Interfacial properties of self-reinforced composite poly(methyl methacrylate)

The authors describe ten years of experience in breast reconstruction in the Department of Plastic and Reconstructive Surgery in the District Hospital of Santarém--Portugal. Ninety-nine patients were treated with 106 reconstructions, most of these were immediate and some were delayed. The authors were interested in providing an adequate volume, but also into obtaining an acceptable aesthetic result. This contributes considerably to the psychological recovery of the patients.     

Long-circulating nanoparticles bearing heparin or dextran covalently bound to poly(methyl methacrylate)

PURPOSE: In a biomimetic approach to the development of drug carriers escaping early capture by phagocytes, nanoparticles made of amphiphilic copolymers of either heparin or dextran and methyl methacrylate were evaluated relative to their in vivo blood circulation time. They were compared to bare PMMA nanoparticles. METHODS: Owing to the fluorescent properties of the covalently attached N-vinyl carbazole, the particles could be detected directly in mouse plasma. Samples were drawn at different time intervals and fluorescence was recorded. RESULTS: After an initial phase of elimination from the blood with a half-life of 5 h, the remaining heparin nanoparticles circulated for more than 48 h and were still detectable in the plasma at 72 h. Dextran nanoparticles were also eliminated very slowly over 48 h. Bare poly (methyl methacrylate) nanoparticles were found to have a half-life of only 3 min. CONCLUSIONS: Both types of nanoparticles proved to be long-circulating. The potent capacity for opsonisation of the poly(methyl methacrylate) core were hidden by the protective effect of either polysaccharide, probably due to a dense brush-like structure. In the case of heparin nanoparticles, the "stealth" effect was probably increased by its inhibiting properties against complement activation.     

Contrast sensitivity in patients with silicone intraocular lenses

Meningococcal clone ET-15/37, which appeared as a new one in the Czech Republic in 1993, caused an emergency epidemiological and clinical situation in invasive meningococcal disease, characterized by a high fatality rate (20%) compared to the "normal" fatality rate due to "non ET-15/37" strains. Morbidity rate increased since the first year of the new clone occurrence and reached the peak in 1995. This clone has spread all over the country and investigation of the epidemiological markers of Neisseria meningitidis allowed to quickly recognize the emergency situation and subsequently to provide a targeted vaccination with A + C polysaccharide meningococcal vaccine which prevented the spread of the disease caused by Neisseria meningitidis C. The most frequent phenotype of ET-15/37 clone was C:2a:P1.2(P1.5) and its percentage achieved 80% of group C Neisseria meningitidis strains tested. This antigenic shift of Neisseria meningitidis was associated with the age shift in invasive meningococcal disease morbidity: teenagers started to be the most affected age group and later age group of 1-4 olds followed with high morbidity rates. In 1995 B variant of ET-15/37 clone, B:2a:P1.2(P1.5), appeared, causing a high fatality rate, too. Some data are indicative of a possible decrease in the invasive meningococcal disease incidence in the Czech Republic; nevertheless, the active surveillance and detailed investigation of meningococci have to be continued. After four years following the vaccination and chemoprophylaxis strategy recommended in the Guidelines, set up by the National Reference Laboratory for Meningococcal Infections in 1993, it is possible to conclude, that there have been practically no secondary cases of invasive meningococcal disease in the Czech Republic.     

Bending and fracture toughness of woven self-reinforced composite poly(methyl methacrylate)

Loosening remains an impediment to the long-term success of total hip replacements despite numerous improvements in the materials used. In cemented prostheses, fatigue and fracture of bone cement have been implicated in the failure of these devices. A new material, self-reinforced composite poly(methyl methacrylate). (SRC-PMMA), has been developed. SRC-PMMA is formed by a novel processing method that will be described. The composite consists of high strength, highly oriented PMMA fibers embedded in a matrix of PMMA. Using a woven form of SRC-PMMA, an in vitro physical and mechanical evaluation was performed to assess the feasibility of its use in an orthopedic prosthesis. Three different weaves of SRC-PMMA were evaluated in bending and fracture toughness in air, after immersion for 30 days in 37 degrees C saline, and after gamma irradiation followed by immersion. Bending modulus and strength were decreased by gamma irradiation followed by saline immersion. The effect of saline immersion alone on bending strength and modulus was negligible. Saline immersion and gamma irradiation followed by saline immersion was shown to have little or no effect on the fracture toughness of woven SRC-PMMA. Differences in the fracture processes of the different weaves were found and can be related to the differing orientation of fibers to the fracture toughness pre-crack. Optimally incorporated SRC-PMMA absorbs the same amount of water as bone cement. Comparison to previous and current work with bone cement controls shows that SRC-PMMA is a material equal to or better than bone cement in all tests performed. It deserves further consideration as a candidate biomaterial.     

由大分子PMMA-DPE引发制备Poly(St-alt-MAn)微球

在1,1-二苯基乙烯(DPE)存在下,以甲基丙烯酸甲酯(MMA)为初始单体,偶氮二异丁腈(AIBN)为引发剂,采用本体聚合法制备出含有DPE片段的大分子引发剂PMMA-DPE;然后以PMMA-DPE为引发剂,以苯乙烯(St)和马来酸酐(MAn)为共聚单体,乙酸异戊酯为溶剂,采用自稳定沉淀聚合法制备了单分散的聚(苯乙烯-马来酸酐)(Poly(St-alt-MAn))的微球.研究了PMMA-DPE的用量对聚合物微球的形态、粒径大小及分布的影响.采用FT-IR,UV-Vis,1H-NMR和GPC对产物的结构进行了表征,并用SEM观察了聚合物微球的形貌.结果表明,PMMA-DPE能够引发St和MAn的共聚合,随着PMMA-DPE用量的增加,聚合反应的转化率呈增大趋势,聚合物微球的粒径呈下降趋势,而粒径分布系数略有增大.     

Bond strength of six soft denture liners processed against polymerized and unpolymerized poly(methyl methacrylate)

The bond strength of six commercial soft denture liners was evaluated by a two-phase tensile test. The soft denture liners investigated were VinaSoft, Prolastic, Flexor, Molloplast-B, Novus, and SuperSoft. The samples were fabricated by processing them (1) against polymerized poly(methyl methacrylate), and (2) against unpolymerized poly(methyl methacrylate). The soft denture liners were processed according to the manufacturers recommendations. The samples were tested using an Instron Universal Testing Machine. The mode of failure, adhesive or cohesive, was also recorded. The bond strength when processed against unpolymerized poly(methyl methacrylate) ranged from 0.48 to 2.60 MPa, and when processed against polymerized poly(methyl methacrylate) the bond strength ranged from 0.94 to 2.56 MPa. A two-way analysis of variance (P = .05) revealed a significant increase in bond strength when the liners were processed against polymerized poly(methyl methacrylate), except for Novus, which had no change, and VinaSoft, which decreased. The Tukey interval between materials was .22 and between methods of polymerization was .08. Four of the six liners investigated demonstrated increased bond strength when processed against polymerized poly(methyl methacrylate). It was concluded that bonding can be influenced by the processing method.     

Ce(DBM)3Phen doped poly(methyl methacrylate) for three-dimensional multilayered optical memory by femtosecond laser

The formation of submicrometer voids within Ce(DBM)3Phen doped poly(methyl methacrylate)(PMMA) was reported under multiphoton absorption excited by an infrared laser beam. The absorption spectra, photoluminescence and electron spin resonance (ESR) spectra before and after femtosecond laser irradiation were discussed. An ultrashort-pulsed laser beam with a pulse width of 200 femtosecond at a wavelength of 800 nm was focused into doped PMMA. The large changes in refractive index and the fluorescence associated with a void allowed conventional optical microscopy and reflection-type confocal microscopy to be used as detection methods. Voids could be arranged in a three-dimensional multilayered structure for high-density optical data storage. The separation of adjacent bits and layers were 4 and 16 μm, respectively.     

The reduction of humeral fracture in pigeons with intramedullary poly (methyl methacrylate) and neutralization plate fixation

The reduction of experimental humeral fracture in pigeons was performed with intramedullary bone cement (poly (methyl methacrylate): PMMA) and neutralization plate fixation to investigate the effect on bone fracture healing and the recovery of flying ability. As a result, neither plate nor bone cement fixation held for more than 2 weeks, but not refracture was observed in any cases with both plate and bone cement. In the latter group, it was confirmed by flight tests that almost normal flying ability was recovered in 6 weeks. In pathological findings, blood supply to the fractured ends recovered within 2 weeks and no cortical bone necrosis was observed at the time except for a disturbance of endosteal callus formation. The process of fracture healing on the plate side took place slightly later than that on the non-plate side, and when much PMMA remained between the fractured ends of the cortical bone the bone formation became spongioid. In view of the quick recovery of flying ability, however, plate and bone cement fixation is considered appropriate to prevent the displacement of a humeral fracture in the pigeon.     

Twenty-two year's experience with intraocular lenses (author's transl)

The employment of the intraocular lens is an acceptable procedure in selected cases. It has great optical and practical advantages over conventional treatment. In the evaluation of suitable cases, clinical considerations, indications and contraindications are of major importance. The extraction of the opaque cataractous lens from the human eye is an eternally new, ever exciting operation which always has challenged the skill of the ophthalmic surgeon. It is not easy and it always involves a risk. The additional demands of technique incurrent in the insertion of the intraocular pupillary lens render the operation still more difficult and increase the risks. The results presented and the advantages achieved justify, in my opinion, the use of an intraocular lens in selected cases of cataract extraction.     

Scanning electron microscopy of intraocular lenses (author's transl)

Tolerance of intracular lenses is partly depending of the finishing quality of their different constituents. Several types of intraocular lenses have been studied with scanning electron microscopy: some imperfections of loop insertions and edge finish have been visualized.     

Spontaneous dislocation into the vitreous of a poly(methyl methacrylate) disc lens 9 years after surgery

A 76-year-old woman had sudden visual loss 9 years after an extracapsular cataract extraction with implantation of a poly(methyl methacrylate) disc intraocular lens (IOL) in the capsular bag. Slitlamp examination showed the disc IOL had luxated into the vitreous through a linear inferior opening in the capsular bag; the IOL lay on the retinal surface. A pars plana vitrectomy was performed. The vitreous cavity was filled with perfluorocarbon liquid, floating the IOL to behind the iris. The IOL was removed through a limbal incision, then another type of IOL was implanted in the ciliary sulcus using transscleral fixation. Thirty days after surgery, best corrected visual acuity (BCVA) was 20/20. At 2 months, total retinal detachment appeared with a large superior retinal dialysis. Another pars plana vitrectomy was performed and the scleral-fixated IOL removed through a limbal incision. Internal gas tamponade was used. The eye was left aphakic. Final BCVA was 20/25.     

Drug release from drug-polyanion complex tablets: poly(acrylamido-2-methyl-1-propanesulfonate sodium -co- methyl methacrylate)

A new erodible, anionic carrier for cationic drugs has been synthesized for oral drug delivery systems. The release properties of tablets prepared from this new material, poly(acrylamido-2-methyl-1-propanesulfonate sodium -co- methyl methacrylate) (PAMPSNa/MMA), are discussed. Pseudo-linear release profiles were obtained and the hydrophobicities of both the polymeric carrier and the bound drugs were found to be an important controlling factor in determining the slopes of these release profiles. The effect of the tablet geometry on the shape of the release profiles was also investigated and tablet thickness was demonstrated to be another key parameter controlling both the linearity of the release profiles, as well as the duration of drug release. The release kinetics are strongly dependent on the drug solubility rather than on the type of amine in the drug (i.e. secondary and tertiary amines). The release of drugs from tablets of drug-PAMPSNa/MMA complexes were well described by the dissociation/erosion mechanism.