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Biomedical subjects

N Pfeiffer

Publications and source records attributed to N Pfeiffer.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Late dislocation of a plate haptic silicone lens into the vitreous body after Nd:YAG capsulotomy. A case report].

UNLABELLED: We describe a case that was referred 10 months after Nd:YAG laser treatment with a posteriorly dislocated silicone intraocular lens (IOL) into the vitreous cavity. PATIENT: A 70-year old white woman underwent uncomplicated phacoemulsification with in-the-bag placement of a Chiron silicone plate haptic lens through a 5.5- mm continuous circular capsulorhexis. The patient was fine until 9 months postoperatively when she complained of a decrease in visual acuity due to capsular fibrosis. A successful Nd:YAG laser capsulotomy was performed, resulting in an increase in visual acuity. Ten months later, the patient noted acute and atraumatic loss of vision, and the IOL was found to have dislocated posteriorly onto the retina. RESULTS: The dislocated IOL was removed via the anterior chamber following pars plana vitrectomy. Perfluorocarbon liquid was used to elevate the slippery lens from the retinal surface. The IOL was removed by a Sato Knife from the anterior chamber, followed by implantation of a one-piece PMMA IOL in the ciliary sulcus. CONCLUSION: Silicone plate haptic IOLs seem to present special risks for dislocation. Shrinkage of the anterior capsule exerts centripetal forces on the ends of the plate haptic, causing the optic to move posteriorly and to exert pressure against the posterior capsule. If either the posterior or anterior capsule is disrupted by Nd:YAG laser treatment, the forces created by capsular contraction against the flexible lens may cause extension of radial tears and appear to be a substantial risk for further capsule-tearing, releasing the IOL into the vitreous cavity, even months later. The forces of capsular contraction can impart a spring-loading effect on plate haptic silicone lenses. Due to inadequate capsular adherence, these lenses are at risk of posterior dislocation from capsular rents following Nd:YAG laser treatment.

Aged↗
PubMed1998

[Adhesion of liquid perfluorocarbon to various intraocular lens materials. A light microscopy study].

INTRODUCTION: Perfluorocarbone liquids (PFCL) enable explantation of intraocular lenses (IOL) dislocated into the vitreous. Because of their relatively high specific weight, the IOL can be floated off the retina and repositioned in the anterior segment. If the IOL surface is affected by contact with PFCL is still unknown. We were interested in the extent of PFCL contact with different IOL materials, having in mind a repositioning of a dislocated IOL into the posterior chamber. We investigated the adherence of PFCL to different IOL surfaces. MATERIALS AND METHODS: The following IOL materials were tested: Group I: acrylate/methacrylate polymers: (a) PMMA, compression molding; (b) PMMA, compression molding, heparin-surface modified; (c) poly-hydroxyethylmethacrylate (polyHEMA); (d) phenylethylacrylate, phenylethylmethacrylate; (e) methylmethacrylate, HEMA; (f) methylmethacrylate, hydroxyethylmethacrylate, ethylene glycol dimethacrylate; (g) hydroxyhexylmethacrylate, HEMA. Group II: silicone elastomers: (a) polydimethylsiloxane; (b) polydimethyldiphenylsiloxane. A total of 17 types of standard quality IOLs were obtained from several manufacturers. Each IOL was immersed in PFCL for 3 h. Then each IOL was rinsed with 2 ml balanced salt solution (BSS) and investigated by light microscopy with regard to the extent of PFCL adhesion. RESULTS: After rinsing with BSS, no PFCL was detectable on any IOL surface. Possible PFCL invasion into an open optic-haptic junction in three-piece IOLs could not be excluded using this method. All IOLs demonstrated optic and haptic surfaces without alterations. The IOL surfaces were comparable to those of new IOLs. CONCLUSIONS: With respect to PFCL-IOL interaction, all IOLs seem to be inert. After luxation of the IOL into the vitreous and IOL elevation by using PFCL, repositioning of the dislocated IOL seems to be possible under special conditions (adequate total diameter, IOL without damage, no open haptic junction in the optic). After rinsing the explanted IOL with BSS prior to reimplantation, the risk of damaging the eye by PFCL remnants on the IOL appears neglibile.

Fluorocarbons↗
PubMed1998

[An ophthalmologic image databank on the Internet].

The Internet has become a powerful, international source for information, and it has shown an exponential growth because of the ease of access and the immediate availability of information. We introduced a new ophthalmological atlas including ICD coding on the World Wide Web. So far, more than 500 lantern slides of typical and interesting ophthalmological findings have been selected and digitized. These pictures were integrated in a data base, which was arranged for ease and speed of search and retrieval. In its background, the data base contains a list of over 4700 ICD-encoded diagnoses to which the picture-documented findings are linked. Comments on pictures can be added by the author or by users. The data base contains several lists, such as a list of ICD codes and diagnoses, a list of all pictures with corresponding diagnoses, a list of all diagnoses and number of pictures, a list of those diagnoses for which the corresponding picture is available, as well as a list of comments on each picture. Special program scripts handle the user's search key words for diagnoses and extract the required information out of the data base, using Windows NT. Search results are presented on an automatically built-up webpage. To provide fast speed of search all pictures initially are shown in a small format (thumbnails) with little amount of data. The related full-size picture is retrieved by a single mouse click. Moreover, the name and institution of the author, diagnostical hints and comments on pictures by the author or by users are offered for each diagnosis available. The Giessen Ophthalmological Picture Atlas can be reached under www.med.unigiessen.de in the Internet. It allows a fast search free of charge from all over the world and, therefore, offers an additional option to obtain specific ophthalmological information for various purposes.

Databases, Factual↗
PubMed1998

[Trabeculotomy, deep sclerectomy and viscocanalostomy. Non-fistulating microsurgical glaucoma operation ab externo].

Filtering procedures have been the gold standard in glaucoma surgery for more than 30 years. Trabeculotomy, deep sclerectomy, and viscocanalostomy might become the procedures of first choice in the future. These new, non-penetrating procedures have not yet been compared to filtering procedures in prospective randomized studies with long-term follow-up. In addition, it is not really known how they modify outflow of the aqueous humor. The surgical technique is described and the most likely underlying effects are discussed.

Adult↗
PubMed1998

[Observations on the pH value of various artificial tears preparations].

BACKGROUND: The pH-values of artificial tears have not been examined up to now. MATERIALS AND METHODS: The pH-values of 20 commercially available artificial tears were determined. RESULTS: pH-values measured from 4.82 to 8.39. One sixth showed pH-values above physiological values. CONCLUSION: A remarkable proportion of commercially available artificial tears deviate from the physiological range of the pH. It does not seem advisable to apply those in eyes with damaged anterior segments.

Germany↗
PubMed1997

Real-time control for transscleral cyclophotocoagulation.

BACKGROUND: In transscleral cyclophotocoagulation, the surgeon cannot directly observe the applied laser effects. Overdosage, possibly resulting in unwanted pop effects, or underdosage with no therapeutic effect therefore often occur. METHOD AND MATERIALS: Laser radiation passing through the sclera and ciliary body is partly reflected from the fundus and can be monitored from outside the eye by a detector system. Since all other parameters influencing the intensity of the recorded radiation are constant in time during one laser exposure, the time dependence of this radiation directly reflects the change of transmission of the treated tissue. The laser exposure therefore can be stopped by a computer when certain criteria of the recorded curves are fulfilled. In addition, the transmission curves are displayed on a monitor in real time, permitting the surgeon to interrupt the exposure. A Nd:YAG laser and a diode laser are connected to the device. After successful tests in enucleated porcine eyes which were evaluated histologically and in human cadaver eyes this method is applied to patients suffering from refractory glaucoma. RESULTS: The transmission curves from enucleated porcine eyes show that the 810-nm diode laser is more appropriate for this method than the 1064-nm. Nd:YAG laser, because the radiation output of the diode is more stable in time and the tissue absorption is higher, both resulting in a larger dynamical range of useful signal. The curves from the porcine eyes, the human cadaver eyes and the curves from patients show a typical shape which allows interruption of exposure either by the surgeon or by the computer program before a pop effect occurs. CONCLUSIONS: This new method increases the precision and safety of transscleral cyclophotocoagulation.

Adult↗
PubMed1997

[Reduction of endothelial cell number by cataract operation with intraocular thymoxamine administration. A randomized, double-blind study].

BACKGROUND: Thymoxamine, an alpha-1-receptor blocker, considerably enhances miosis when given intraocularly in combination with acetylcholine. We investigated whether intraocular use of thymoxamine 0.02% reduced the number of endothelial cells. PATIENTS AND METHODS: After phacoemulsification of 59 eyes, either thymoxamine 0.02%, acetylcholine 1.0% or buffered saline solution was given intraocularly. With a contact specular microscope, corneal endothelial cell photographs were taken on the day before treatment and 3 days and 6 weeks after surgery. RESULTS: There were no statistically significant differences between endothelial cell counts of eyes treated with thymoxamine (-7.2%), acetylcholine (-10.2%) or BSS (-9.4%). CONCLUSION: This study shows for the first time that thymoxamine, when given in the anterior chamber after phacoemulsification, does not cause a greater loss of endothelial cells than acetylcholine or buffered saline solution.

Acetylcholine↗
PubMed1997

[Acute retinal necrosis. Silicon oil tamponade in retinal detachment].

BACKGROUND: Because retinal necrosis syndrome seldom occurs, we present our results of silicone oil tamponade for associated retinal detachment. PATIENTS AND METHODS: Thirteen eyes from 13 patients undergoing retinal reattachment surgery for retinal detachment associated with acute retinal necrosis in a consecutive series between January 1988 and June 1995 were followed up. Patients were 25 to 56 years of age. Four patients had acquired immune deficiency syndrome (AIDS). Five eyes that were operated on with cryopexy and scleral buckling received vitrectomy, membrane peeling, silicone oil tamponade and endolaser treatment in a second operation. Eight eyes were primarily operated on with cryopexy, encircling buckle, vitrectomy with membrane peeling, silicone oil tamponade and endolaser treatment. All patients were treated with acyclovir. RESULTS: Postoperative complete reattachment was observed in 12 eyes and persistence of a peripheral detachment in one eye. Vision improved in eight eyes, but only five eyes achieved 20/200 or better vision. Limited functional results in our series were caused by retinal ischemia, optic atrophy and macula scars. After a median of 9.3 months silicone oil was removed in nine eyes. No retinal redetachment or recurrent retinitis was observed during a follow-up time of at least 6 months. CONCLUSIONS: Vitrectomy and silicone oil tamponade allowed all cases of retinal detachment associated with acute retinal necrosis to be successfully repaired. Further studies must be conducted to find out how we can improve the visual outcome-perhaps by earlier therapy with acyclovir or earlier vitrectomy.

Acquired Immunodeficiency Syndrome↗
PubMed1997

[Long-term stability of heparin-coated PMMA intraocular lenses. Results of an in vitro study].

UNLABELLED: The surface modification of PMMA-intraocular lenses (IOLs) demonstrated a blood-aqueous-barrier protective effect and reduced the incidence of IOL depositions and postoperative fibrin exudation, especially in risk patients (e.g. pediatric cataract, diabetes mellitus, recurrent uveitis). The long-term stability of the surface modification via phenylimines, which permit a covalent surface linkage of heparin to synthetic polymeric materials by reductive amination, is still unknown. MATERIAL AND METHODS: Four heparin surface-modified (HSM) monofocal and two unmodified monofocal sterile PMMA-IOLs were stored in an aqueous-serum mixture at 37 degrees C over a period of 4 years and 1 months with daily rotation. After 4 years the concentration of surface-bound heparin on two HSM-IOLs of this mixture and two brand-new HSM-IOLs were determined using an orcin-assay after initial heparinase treatment. Four years after incubation, the modified toluidine blue staining method was used to examine the surface-bound heparin on synthetic polymers. This staining technique with toluidine blue, a non-protein basic substance, enables examination and analysis of the homogeneity of the mono-molecular heparin layer even under critical conditions because of its homogeneous staining. Light and scanning electron microscopic examination of the IOL surfaces were subsequently performed. RESULTS: The concentration of heparin (microgram/cm2) on the IOL surface after 4 years of incubation and treatment with heparinase was valued at 0.51 +/- 0.05 and 0.53 +/- 0.04 in the two brand-new HSM-IOLs. A slightly coarsegrained complex agglutination on the IOL surface was detected by the toluidine blue staining method. Light and spectral microscopy of the surface of the stained IOLs as well as scanning electron microscopy of all HSM-IOLs showed a homogeneous heparin structure and coating after 4 years of in vitro storage. No signs of desorption or reduced reactivity of the heparin were observed in comparison with new HSM-IOLs. The unmodified PMMA-IOLs did not stain, as expected. CONCLUSION: The heparin-modified surface of the examined PMMA-IOLs was intact even after 4 years of storage in an aqueous serum solution. A long-term benefit, in addition to the advantages of the hydrophilisation in the immediate postoperative period, especially for risk patients, is therefore suggested.

Drug Stability↗
PubMed1997

[Treatment of cavernous hemangiomas with the neodymium:YAG laser].

BACKGROUND: Cavernous hemangiomas are benign vascular lesions which are apparent at birth or soon thereafter. Although hemangiomas involute spontaneously, cosmetically unacceptable results or life-threatening complications may occur, necessitating early therapy. METHODS AND PATIENTS: Thirty-four patients with facial cavernous hemangiomas were treated with a cw-neodymium:YAG laser. Before, during, and after the treatment the skin was cooled with ice. The quartz fiber was used in contact or non-contact technique, and in very large hemangiomas we used interstitial treatment. RESULTS: In all patients a clear reduction of the tumor size was achieved. In 26 cases the tumor disappeared completely. Usually there is considerably swelling of the tumor immediately after treatment which decreases within some days. Side effects include local hyperemia and slight burns. Scarring was seen in only two cases. CONCLUSIONS: Facial cavernous hemangiomas can be treated satisfactory by the neodymium:YAG laser. Safe, active intervention with this laser is possible in most, if not in all, cases and it provides an alternative to other treatment modalities including the neglect of these lesions.

Adolescent↗
PubMed1997

[Interaction of silicone oil with various intraocular lenses. A light and scanning electron microscopy study].

BACKGROUND: Silicone oil is increasingly used as an intravitreal tamponade in severe forms of vitreoretinal disorders, also in pseudophakic eyes. In some patients silicone oil was observed to be adherent to the intraocular implant. MATERIAL AND METHODS: To investigate the interaction of silicone oil with IOL-materials and the influence of lipoproteins of the serum on this interaction we used the following in vitro experimental set-up: Sterile IOLs of different IOL-materials (e.g. PMMA, silicone, hydrogel) and surface-modifications (e.g. Pharmacia 809P and 809C, Soflex LI41U, Alcon AcrySof M60BM, Allergan SI-30NB, SI-40NB, Chiron adatomed 90D, C10 and C31UB, MemoryLens U940A, Corneal ISHEMA 66, Storz H60M) were stored in vitro together with silicone oil (1000 centistokes) with and without a fresh serum solution at 37 degrees Celsius. This combination was rotated slowly and mixed thoroughly three times a day. After 3 and 6 months and a standardized special preparation in an ultrasound bath and air treatment, the IOLs were examined by light microscopy followed by scanning electron microscopy. RESULTS: Silicone oil strongly adhered to holes and to the IOL surface especially in silicone and PMMA IOLs. Highly hydrophylic IOLs-like the heparin-surface-modified and hydrogel IOL-cleared from silicone oil relatively early. This effect was more pronounced in the group with lipid-/serum solution than without. In some silicone IOLs silicone oil was strongly adherent to the lens and it was nearly impossible to wash off the oil even when using an alcoholic solution. One silicone IOL lost its haptics in the serum-oil-IOL-mixture, another lost small particles from the IOL surface. CONCLUSION: Silicone oil is more adherent to hydrophobic IOLs than to hydrophylic IOLs. Lipoproteins of the serum play an important role in facilitating an effect of silicone oil on IOL materials. We recommend highly hydrophylic especially surface-modified IOLs for lens implantation following vitreoretinal silicone oil surgery. Implantation of silicone IOLs in vitreoretinal high risk eyes should be avoided.

Equipment Failure Analysis↗
PubMed1997

[Extent of damage to different intraocular lenses by neodymium:YAG laser treatment--an experimental study].

BACKGROUND: Neodymium:YAG laser capsulotomy frequently damages the intraocular lens (IOL). This damage, mainly caused by acoustic shock wave and thermal conduction, results in opacities in the IOL, which may cause glare or image degradation. Because of the introduction of new IOL materials in cataract surgery, investigation of YAG laser resistance of these IOL materials seems to be necessary. MATERIALS AND METHODS: A total of 17 standard IOLs of different types and classes of materials were tested as follows: Class I: Acrylate a) PMMA, compression molding, b) PMMA, compression molding, heparin-surface modified, c) acrylate/methacrylate copolymer; Class II: Silicone: a) Polydimethylsiloxane, b) Polydimethyldiphenylsiloxane; Class III: Hydrogel: a) poly-hydroxyethylmethacrylate (poly-HEMA), b) polyacrylate-hydrogel; Class IV: Thermoset polymer: methylmethacrylate, hydroxyethylmethacrylate, ethylene glycol dimethacrylate. Each IOL was placed in a rectangular transparent acrylic test chamber filled with balanced salt solution and subjected to irradiation from a Q-switched Nd:YAG laser. The laser beam was focused on the posterior surface and inside of the IOLs. The optic of the IOL was divided into four target zones and each zone was subjected to 40 bursts inside the lens and 40 bursts on the posterior surface of the lens. Laser power settings were: 1.1 mJ, 1.1 mJ with 0.4 mm defocus, 2.1 mJ and 4 mJ and one burst was applied (wave length 1064 nm, fundamental mode, duration 7 +/- 2 nanoseconds, spot size 15 microns in air). Following exposure, each lens was examined by light microscopy for the interior damage and by scanning electron microscopy for the posterior surface damage. For quantitative analysis, the extent of each superficial damage was evaluated by an image analysis system using at least original magnification x 1400. RESULTS: Each IOL material demonstrated specific morphologic damage patterns. Intralenticular damage: Class I: cracks with radiating fractures with smaller extent in group Ic; Class II: blistered snowball-like inclusions; Class III: localized small holes, exception: IIIb: with very short radiating fractures; Class IV: stellar pits with short radiating fractures. For silicone superficial posterior damage sites a splash crater pattern with irregular melted edges was observed, while acrylate damage sites demonstrated a melted or stellate crater pattern with slightly raised edges. The silicone, poly-HEMA and the acrylic IOLs containing HEMA presented highest YAG laser resistance with the smallest amount of posterior damage in comparison to PMMA-IOLs. There was no marked increase in damage size in these IOL materials with higher energy exposure in this set-up. CONCLUSION: For each material consistent and characteristic specific morphologic damage patterns were observed. Foldable optic materials were more resistant against Nd:YAG-laser photodisruption than rigid optic materials. Individual laser strategies for each IOL-material and design should be deducted.

Capsulorhexis↗
PubMed1997

Effect of head position on refraction in aphakic and phakic silicone-filled eyes.

BACKGROUND: The refraction of the eye is altered significantly after the instillation of silicone oil into the vitreous cavity because of the silicone oil's high refractive index. The degree of the refractive change shows diurnal variation and depends on the patient's head position. PATIENTS AND METHODS: To analyze the degree and time course of refractive changes with respect to head position, the authors performed objective refraction in five aphakic and five phakic silicone oil-instilled eyes with attached maculae using an automatic hand-held refractometer. In each patient, 25 measurements were taken at short intervals using a hand-held autorefractometer with the patient in different positions (supine, head tilted down, and primary eye position). RESULTS: The highest shift of refraction was +5.95 +/- 2.63 diopters spherical equivalent in aphakic eyes and +2.45 +/- 0.71 diopters in the phakic eyes after the patient's position was changed from supine to head tilted down. Three minutes after the position change the refractive shift was stable in almost all eyes. Only slight changes in cylinder and the respective corresponding axis with a mean cylinder shift of 10.1 +/- 5.1 degrees were noted. CONCLUSIONS: Immediately after the head position was changed, aphakic eyes demonstrated more pronounced refractive shifts than phakic eyes. The results of this study explain patients' reports of diurnal changes in visual acuity after intraocular silicone oil instillation. Refractive changes caused by silicone oil stabilized a few minutes after a change in head position.

Aphakia, Postcataract↗
PubMed1997

A new method for direct detection of heparin on surface-modified intraocular lenses. A modification of Jaques' toluidine blue staining method.

BACKGROUND: Examination of surface-bound heparin on synthetic polymers can only be performed by few staining methods. These methods are limited by an only approximate detection of heparin visible at high magnification. Other methods only measure heparin quantitatively (per square dimension) and are rather sensitive to artifacts. Due to its homogeneous staining pattern, the modified toluidine blue staining technique, using a non-protein-based substance, allows examination and analysis of the homogeneity of the monomolecular heparin layer even under critical conditions like scanning electron microscopy. MATERIALS AND METHODS: For critical examination of the heparin layer, this method was used for 5 sterile heparin surface-modified (HSM) monofocal (Pharmacia, 809C, 5 mm optical zone), 2 multifocal PMMA (Pharmacia, 811E, 6 mm optical zone) and 1 standard PMMA intraocular lenses (IOLs; Pharmacia, 809P, 5 mm optical zone). A special mixture containing a sodium borate buffer was used to avoid cross-reactions of toluidine with phenylimines, which permit a covalent surface linkage of heparin to synthetic polymeric materials via reductive amination. This resulted in less coarse-grained complex agglutination. After light and spectral microscopy of the surface of stained IOLs, scanning electron microscopy was performed to investigated the reliability and validity of this modified staining method. RESULTS: All HSM IOLs showed a homogeneous heparin structure and coating, which could be demonstrated even under critical photographic circumstances. CONCLUSIONS: The modification of the original toluidine blue staining method introduced by Jaques in 1943 is a reliable and reproducible technique for the detailed in vitro analysis of surface-bound heparin with a low artifact rate. Because of the detailed detection of heparin on polymeric surfaces, this staining method is recommended for special problems, e.g. in cataract surgery.

Coloring Agents↗
PubMed1997

[Endophthalmitis after cataract surgery: long-term follow-up].

BACKGROUND: Endophthalmitis is a serious complication after cataract surgery. PATIENTS AND METHODS: Therefore, a retrospective study was performed by reviewing patient-records of all cases of end-ophthalmitis after catract surgery that were treated at the department of ophthalmology of the University Hospital in Mainz between January 1986 and December 1995. RESULTS: 44 eyes were treated for endophthalmitis. Of those, 38 had been referred. In 15 eyes cataract surgery was performed on an outpatient basis. In 20 cases the onset of end-ophthalmitis occurred within the first postoperative week. We isolated staphylococcus epidermidis (14), staphylococcus aureus (4), other gram-positive microorganisms (15), gram-negative bacteria (2) and candida (1). As risk factors we found a wound dehiscence (14), an intraoperative loss of vitreous (11), diabetes (11), skin-diseases like rosacea or neurodermatitis (6). In 36 cases a vitrectomy was performed. After a mean follow-up of 25 +/- 22 months 26 patients had a visual acuity of 0.05 or better. CONCLUSION: Gram-positive bacteria showed to be the most common causetive microorganisms. In a third of all cases the sample demonstrated no growth. More than 80% of the eyes were treated by vitrectomy. About 60% of the patients obtained a visual acuity of 0.05 or better.

Adult↗