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Biomedical subjects

L Werner

Publications and source records attributed to L Werner.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Postoperative opacification of posterior chamber intraocular lenses - a review].

Postoperative opacification of intraocular lenses (IOLs) is a very unpleasant complication for the ophthalmic surgeon and the patient. We report on our experiences with opacification of different foldable IOL designs and rigid poly (methyl methacrylate) (PMMA) posterior chamber lenses.1. Snowflake degeneration of PMMA IOLs: This condition is an unanticipated and surprising late postoperative finding 8 to 15 years after implantation. In our opinion, this complication is probably not related to the PMMA biomaterial itself, but rather it appears to represent a manufacturing problem that has affected a selected, albeit large number of lenses manufactured in the 1980s-mid 1990s.2. Degeneration of UV absorber material and calcium deposits within the optic of hydrophilic IOLs: Two years postoperatively degenerations of UV absorber material and calcium deposits within the optic of single piece hydrophilic acrylic lenses SC60B-OUV manufactured by MDR (Medical developmental research Inc. Clearwater FL, USA) can occur. Although the precise mechanism is not fully known, it was assumed that these opacifications are due to premature aging of the UV blocking agent incorporated in the lens biomaterial and calcification.3. Calcification on the surface of the Bausch & Lomb Hydroviewtrade mark IOLs: Twelve to 15 months postoperatively granular surface calcifications in Hydroviewtrade mark IOLs occured. The mechanism is not fully understood. According to Bausch and Lomb studies, part of the components of the packaging contained silicone, which may have come off the packaging onto the lens optic, where it then appears to be a catalyst for calcium precipitation. The manufacturer has correlated a change in packaging with the appearance of the opacification. The manufacturer now believes that this problem has been solved. However, final verification will require a careful 1 - 2 years clinical study.4. Glistenings in the hydrophobic acrylic AcrySoftrade mark IOLs: The time frame of glistenings in the AcrySoftrade mark IOLs is highly variable. It has been suggested that the occurrence of glistenings may be related to variations in the temperature of the lens just prior to and or during insertion into the eye. Formation of vacuoles may occur within the submersed acrylic polymer when there is a transient increase and then decrease in temperature during the surgical procedure. "Glistenings" may then subsequently form by ingress of anterior chamber fluid. Contrast sensitivity can been decreased in some patients, but clinically significant decrease of visual acuity has been rare.

Biocompatible Materials↗
PubMed2001

AcrySof acrylic intraocular lens implantation in children: clinical indications of biocompatibility.

PURPOSE: To assess the clinical biocompatibility of AcrySof (Alcon, Ft Worth, Tex) acrylic intraocular lenses (IOLs) in the highly reactive eyes of infants and children. METHODS: A database of 230 pediatric IOL implantations was queried to allow retrospective review of all eyes implanted with an AcrySof IOL. Eyes implanted with polymethyl methacrylate (PMMA) IOLs were also reviewed and were used as a historical comparison group. Follow-up examinations were conducted by the surgeon on postoperative day 1, day 7, week 4, and week 8 and every 3 months during the first year and every 6 months thereafter. The presence of synechiae, lens deposits, and posterior capsule opacification were noted in the record at each visit. Examination notes were photocopied, and data were extracted from each visit note and entered into a computerized database. RESULTS: One hundred and ten eyes had an AcrySof IOL at an average age of 60.4 months and had an average postoperative follow-up of 64.6 weeks. In comparison, 120 eyes had PMMA IOLs inserted at an average age of 71.9 months with an average postoperative follow-up of 136.9 weeks. IOL cell deposits were seen at the slit lamp in 7 of 110 (6.4%) AcrySof lenses as compared with 26 of 120 (21.75%) PMMA lenses (P =.002). Posterior synechiae were seen in 5 of 110 (4.5%) AcrySof lenses as compared with 23 of 120 (19.2%) PMMA lenses (P =.001). Twenty-two AcrySof-implanted eyes had an intact posterior capsule. Twenty-eight PMMA-implanted eyes had an intact posterior capsule. The YAG laser capsulotomy rate was similar in the 2 groups at 45.4% for AcrySof and 50% for PMMA (P =.973). The average time from surgery to YAG posterior capsulotomy was 18.6 months with an AcrySof lens and 18.3 months with a PMMA lens (P =.951; t test). A total of 60 patients (68%) implanted with AcrySof IOLs were able to cooperate for Snellen visual acuities. Of their 67 eyes, 48 (72%) had a 20/40 or better visual acuity at the last follow-up examination, and 63 eyes (94%) had a 20/100 or better visual acuity. Thirty-five eyes (52%) required amblyopia therapy, and patching continues as needed. CONCLUSIONS: The AcrySof IOL is representative of a new group of foldable IOLs made from flexible hydrophobic acrylic material. The AcrySof IOL appears clinically to be biocompatible when placed in the eyes of children despite the increased tissue reactivity known to occur in young patients.

Acrylic Resins↗
PubMed2001

Complications of cataract and refractive surgery: a clinicopathological documentation.

PURPOSE: To present selected complications of keratorefractive and phakic intraocular lens (IOL) surgery and a series of IOLs that required explantation because of various postimplantation opacification of the IOL optic. METHODS: Two specimens obtained after keratorefractive surgery, 2 phakic IOLs, and a total of 23 explanted IOLs from cases in which postimplantation opacification of the IOL optic had occurred were studied. These included 6 Bausch and Lomb (B&L) Hydroview H60 M designs, 9 Medical Developmental Research (MDR) SC60B-OUV designs, and 24 IOLs with rigid PMMA optics that had been implanted in the 1980s and early 1990s. Of the latter, 8 required late explantation because of decreased visual acuity. Analyses performed included gross and light microscopic evaluation, histochemical staining, electron microscopy, and energy-dispersive spectroscopy. RESULTS: We provide examples of 3 postrefractive surgery complications: (1) fungal keratitis after LASIK, (2) post-LASIK corneal decompensation, and (3) cataract formation after implantation of phakic posterior chamber IOLs. Regarding the IOL optic opacities, classifications of 3 types are described: (1) a surface calcification of the B&L Hydroview IOL; (2) diffusion of calcium into the substance of the optic of the hydrophilic "acrylic" SC60B-OUV MDR foldable IOL design, sometimes leading to total opacification of the IOL optic and also its haptics; (3) a distinct pattern of intraoptical opacification with rigid PMMA designs that we term a snowflake degeneration. This term is based on the clinical and pathologic appearance of the individual lesions. Each snowflake lesion represents a focal breakdown of PMMA material as opposed to deposition of exogenous material. CONCLUSIONS: Analysis of complications of refractive surgery represents a new field of ocular pathology. The clinicopathological reports presented here provide an overview of selected complications after refractive surgery. We also help define 3 newly recognized, clinically significant conditions based on postoperative IOL optic opacification. The calcification processes noted on the 2 modern foldable designs studied here (B&L and MDR lenses) need further review by the manufacturers in order to reassess production processes, especially in terms of polymer selection, manufacturing techniques, and other factors required to produce a safe and effective lens. Any lens not meeting today's high standards should not be marketed. The important fact in recognizing the snowflake complication of PMMA IOLs as described here is to alert surgeons about the nature of the lesion so that they will not alarm patients or require extensive and unnecessary testing in trying to determine its pathogenesis. There is no reason why successful explantation cannot be performed in cases where severe visual decrease or loss has occurred.

Calcinosis↗
PubMed2000

Induction of cataracts of varying degrees of hardness in human eyes obtained postmortem for cataract surgeon training.

PURPOSE: To report a method of inducing nuclear cataracts of varying degree of hardness using intralenticular injection of the Karnovsky solution. METHODS: Twelve postmortem human eyes were prepared according to the Miyake-Apple posterior video technique. After performing capsulorhexis and hydrodissection/delineation, 0.2 ml of the Karnovsky solution was injected into the lens nucleus of the eyes. Manual extracapular cataract extraction techniques and various two-handed phacoemulsification maneuvers were then practiced at various time intervals after the injection. RESULTS: Uniform nuclear cataracts with varying degrees of hardness were successfully induced in all globes. The optimum dose of the Karnovsky solution and time for induction of nuclear hardness of grade 3 (ideal for practicing two-handed phacoemulsification maneuvers) were 0.2 ml and 15 minutes, respectively. CONCLUSION: The Karnovsky solution can be successfully used for the induction of hard, uniform nuclear cataracts for learning/practicing extracapular cataract extraction and phacoemulsification.

Cataract↗
PubMed2000

High-frequency ultrasound characterization of microporous biointegrable polymers in cornea using acoustic parameters.

The current work deals with the use of high-frequency quantitative backscatter acoustic microscopy for the evaluation of the biointegration of microporous polymer implants used as support of artificial cornea. A three-dimensional (3-D) 80 MHz ultrasound microscope (25 microns axial resolution at focus) was used for the imaging and characterization of the progressive biointegration of polymers implanted in rabbit cornea. In-vitro and in-vivo studies were performed. Quantitative assessment of the structural changes in the biomaterial was performed using the spectral analysis of the radio frequency signal and the estimation of acoustic parameters in the 10-65 MHz frequency bandwidth. Correlation of in-vitro ultrasound data with histologic findings has shown that attenuation and backscatter coefficients are sensitive to the changes in the polymer pore content with time. Our results obtained in vivo demonstrated that 3-D 80 MHz echography coupled with quantitative characterization provide a unique tool for the non-invasive and objective follow-up of the implant biointegration and should contribute to clinical management of artificial cornea.

Acoustics↗
PubMed2000

Postoperative deposition of calcium on the surfaces of a hydrogel intraocular lens.

OBJECTIVE: To report clinical, pathological and histochemical features of 5 Hydroview intraocular lenses (IOLs) explanted from five patients who had visual disturbances caused by postoperative deposits on the lens surfaces. DESIGN: Noncomparative small case series with clinicopathologic and histochemical correlations. PARTICIPANTS: Five hydrophilic IOLs explanted from five different patients. All patients presented with decreased visual acuity and glare circa 12 months after uneventful phacoemulsification and IOL implantation, associated with a red-brown granularity on the optical surfaces of the IOLs. METHODS: The lenses were explanted, fixed in buffered formaldehyde and examined by gross and light microscopy. MAIN OUTCOME MEASURES: Staining of the IOLs with 1% alizarin red and with the von Kossa method (both stains for calcium). Two additional IOLs were also stained and included as controls. RESULTS: The optical surfaces of all five IOLs were covered by a layer of irregular granular deposits, composed of multiple fine, translucent spherical-ovoid granules. The deposits stained positive for calcium in all cases. No deposit or positive staining was observed on the IOLs haptics. Staining of the control IOLs was also negative. CONCLUSION: This is the first histopathological report of calcified deposits on the surfaces of this hydrogel IOL model. Further studies on other similar cases with this lens should be done to determine the incidence and possible mechanisms of this phenomenon.

Aged↗
PubMed2000

Anterior capsule opacification: a histopathological study comparing different IOL styles.

OBJECTIVE: To compare the degree of anterior capsule opacification (ACO) in human eyes obtained post-mortem containing various rigid and foldable posterior chamber intraocular lens (PC-IOL) designs. DESIGN: Comparative autopsy tissue study with clinicopathologic correlations. MATERIALS: Four hundred sixty human globes containing the following PC-IOL styles were analyzed: (1) one-piece polymethylmethacrylate (PMMA) optic-PMMA haptic (n = 50), (2) one-piece silicone-plate IOL, large hole (n = 40), (3) one-piece silicone-plate IOL, small hole (n = 67), (4) three-piece PMMA optic-PMMA/Prolene haptic (n = 51), (5) three-piece acrylic optic-PMMA haptic (n = 96), (6) three-piece silicone optic-PMMA haptic (n = 24), (7) three-piece silicone optic-polyimide haptic (n = 40), and (8) three-piece silicone optic-prolene haptic (n = 92). TESTING: The globes were sectioned in the equatorial plane for gross examination and then processed through paraffin; sectioned, and stained with hematoxylin-eosin, periodic acid-Schiff, and Masson's trichrome stains; and examined by light microscopy. MAIN OUTCOME MEASURES: Anterior capsule opacification was scored in each eye by grading the histologic sections from 0 to III, according to the amount (thickness) of proliferative tissue and cells measured in sagittal sections on the inner surface of the anterior capsule at the capsulorhexis margin. RESULTS: The difference among the eight groups was significant (P < 0.0001). Mean ACO scores were highest with the large and small hole one-piece silicone-plate lenses (1.77 +/- 0.86 and 1.28 +/- 0.77, respectively). The lowest mean score was observed in the group of three-piece acrylic optic-PMMA haptics lenses (0.51 +/- 0.52). CONCLUSIONS: Our results confirm previous clinical observations that the rate of ACO is relatively high with plate-haptic silicone IOLs. The lowest rate was noted with the three-piece acrylic optic-PMMA haptic IOL. The IOL design and IOL material are significant factors in the development of ACO.

Cataract↗