RESUMEN

PURPOSE/BACKGROUND: In the 'Tübingen Kindergarten study', an orthoptic screening program for amblyopia in three-year-olds was evaluated. In the retrospective analysis presented here, the association between a child's history--especially participation in the regular preventive care examinations in Germany (U4 to U7)--and the time of detection of target diseases was investigated. METHODS AND SUBJECTS: The parents of three groups of children were interviewed by telephone. Group 1 consisted of 21 children already treated for amblyopia before orthoptic screening; group 2 of 26 children with target conditions newly detected by orthoptic screening; and group 3 of 32 children with newly detected moderate ametropia. The groups were tested for differences in history and utilization/results of the regular preventive care examinations. RESULTS: Participation in regular preventive care ranged from 82% to 92%. There were no significant differences between the groups. Nearly 90% of parents from groups 2 and 3 had not heard of amblyopia before orthoptic screening. Only one child had been referred after regular preventive care examinations. CONCLUSIONS: The regular preventive care examinations contributed little to the detection of amblyopia. The strong position of the pediatrician should be used for the early information of parents.

Asunto(s)

RESUMEN

AIMS: To estimate the long term cost effectiveness of treatment for amblyopia in 3 year old children. METHODS: A cost utility analysis was performed using decision analysis including a Markov state transition model. Incremental costs and effects during the children's remaining lifetime were estimated. The model took into account the costs and success rate of treatment as well as effects of unilateral and bilateral visual impairment caused by amblyopia and other eye diseases coming along later in life on quality of life (utility). Model parameter values were obtained from the literature, and from a survey of experts. For the utility of unilateral visual impairment a base value of 0.96 was assumed. Costs were estimated from a third party payer perspective for the year 2002 in Germany. Costs and effects were discounted at 3%. Uncertainty was assessed by univariate and probabilistic sensitivity analysis (Monte-Carlo simulation). RESULTS: The incremental cost effectiveness ratio (ICER) of treatment was euro2369 per quality adjusted life year (QALY). In univariate sensitivity analysis the ICER was most sensitive to uncertainty concerning the utility of unilateral visual impairment-for example, if this utility was 0.99, the ICER would be euro9148/QALY. Monte-Carlo simulation yielded a 95% uncertainty interval for the ICER of euro710/QALY to euro38 696/QALY; the probability of an ICER smaller than euro20 000/QALY was 95%. CONCLUSION: Treatment for amblyopia is likely to be very cost effective. Much of the uncertainty in results comes from the uncertainty regarding the effect of amblyopia on quality of life. In order to reduce this uncertainty the impact of amblyopia on utility should be investigated.

Asunto(s)

RESUMEN

The organic matrix surrounding bullet-shaped, cubo-octahedral, D-shaped, irregular arrowhead-shaped, and truncated hexa-octahedral magnetosomes was analysed in a variety of uncultured magnetotactic bacteria. The matrix was examined using low- (80 kV) and intermediate- (400 kV) voltage TEM. It encapsulated magnetosomes in dehydrated cells, ultraviolet-B-irradiated dehydrated cells and stained resin-embedded fixed cells, so the apparent structure of the matrix does not appear to be an artefact of specimen preparation. High-resolution images revealed lattice fringes in the matrix surrounding magnetite and greigite magnetosomes that were aligned with lattice fringes in the encapsulated magnetosomes. In all except one case, the lattice fringes had widths equal to or twice the width of the corresponding lattice fringes in the magnetosomes. The lattice fringes in the matrix were aligned with the [311], [220], [331], [111] and [391] related lattice planes of magnetite and the [222] lattice plane of greigite. An unidentified material, possibly an iron hydroxide, was detected in two immature magnetosomes containing magnetite. The unidentified phase had a structure similar to that of the matrix as it contained [311], [220] and [111] lattice fringes, which indicates that the matrix acts as a template for the spatially controlled biomineralization of the unidentified phase, which itself transforms into magnetite. The unidentified phase was thus called pre-magnetite. The presence of the magnetosomal matrix explains all of the five properties of the biosignature of the magnetosomal chain proposed previously by Friedmann et al. and supports their claim that some of the magnetite particles in the carbonate globules in the Martian meteorite ALH84001 are biogenic. Two new morphologies of magnetite magnetosomes are also reported here (i.e. tooth-shaped and hexa-octahedral magnetosomes). Tooth-shaped magnetite magnetosomes elongated in the [110] direction are reported, and are distinct from arrowhead-shaped and bullet-shaped magnetosomes. Elongation of magnetite magnetosomes in the [110] direction has not been reported previously. A Martian hexa-octahedral magnetite particle was previously characterized by Thomas-Keptra et al. and compared with truncated hexa-octahedral magnetite magnetosomes. Hexa-octahedral magnetite magnetosomes with the same morphology and similar sizes and axial ratios as those reported by Thomas-Keptra et al. are characterized here. These observations support their claim that ALH84001 contains evidence for a past Martian biota.

Asunto(s)

RESUMEN

AIM: To analyse the test characteristics of orthoptic screening for amblyopia or amblyogenic risk factors (target conditions) in kindergarten. METHODS: 1180 three year old children were screened by orthoptists in 121 German kindergartens. Orthoptic screening consisted of cover tests, examination of eye motility and head posture, and monocular visual acuity testing with the Lea single optotype test. Children were re-examined in kindergarten by different orthoptists after 3-6 months using a more demanding pass threshold for visual acuity. All children with at least one positive orthoptic test result or an inconclusive re-examination were referred to an ophthalmologist for diagnosis. The gold standard was set positive if a target condition was diagnosed on ophthalmological examination. It was set negative if no target condition was found upon ophthalmological examination, or if a child who screened negative or inconclusive passed the orthoptic re-examination without any positive test result. RESULTS: The gold standard was ascertained in 1114 children. 26 (2.3%) children had a "positive" gold standard. In 10.8% of the children the initial screening was "inconclusive," mostly due to lack of collaboration. Screening test sensitivity (based on conclusive results only) was 90.9% and specificity was 93.8%. CONCLUSIONS: Orthoptic vision screening of 3 year olds in kindergarten is sensitive and specific. However, owing to a substantial proportion of inconclusive screening results, rescreening of non-cooperative 3 year old children should be considered.

Asunto(s)

RESUMEN

Highly porous nanocomposites of zirconium dioxide and silicate are synthesised in an aqueous system from an inorganic salt of zirconium; the nanacomposites, with tailorable pore structures, exhibit superior performance as catalyst supports.

RESUMEN

Ophthalmophakometric measurements of ocular surface radius of curvature and alignment were evaluated on physical model eyes encompassing a wide range of human ocular dimensions. The results indicated that defocus errors arising from imperfections in the ophthalmophakometer camera telecentricity and light source collimation were smaller than experimental errors. Reasonable estimates emerged for anterior lens surface radius of curvature (accuracy: 0.02-0.10 mm; precision 0.05-0.09 mm), posterior lens surface radius of curvature (accuracy: 0.10-0.55 mm; precision 0.06-0.20 mm), eye rotation (accuracy: 0.00-0.32 degrees; precision 0.06-0.25 degrees), lens tilt (accuracy: 0.00-0.33 degrees; precision 0.05-0.98 degrees) and lens decentration (accuracy: 0.00-0.07 mm; precision 0.00-0.07 mm).

Asunto(s)

RESUMEN

AIMS: To assess non-cycloplegic screening for amblyopia with the hand held Nikon Retinomax autorefractor in 3 year old kindergarten children. METHODS: 427 three year old children were examined in kindergarten with the Retinomax without cycloplegia. A gold standard was established in all children by two orthoptic examinations in kindergarten. If there were missing, abnormal, or inconsistent findings, children were referred for ophthalmological examination. If, by the ophthalmological examination, a new case of amblyopia requiring treatment was diagnosed, the gold standard was set "positive." RESULTS: In 404 children the gold standard was obtained. 10 children (2.5%) had a "positive" gold standard of unknown and untreated amblyopia. Screening sensitivity was 0.80, specificity 0.58, accuracy 0.58, and the likelihood ratio 1.89. CONCLUSION: Non-cycloplegic refractive screening with the Retinomax led to many false positive referrals due to instrument myopia and "inconclusive" results. Hence specificity, accuracy, and the likelihood ratio were too low to conduct screening effectively.

Asunto(s)

RESUMEN

Non-periodic structural variation has been found in the high Tc cuprates, YBa2Cu3O7-x and Hg0.67Pb0.33Ba2Ca2Cu3O8+delta, by image analysis of high resolution transmission electron microscope (HRTEM) images. We use two methods for analysis of the HRTEM images. The first method is a means for measuring the bending of lattice fringes at twin planes. The second method is a low-pass filter technique which enhances information contained by diffuse-scattered electrons and reveals what appears to be an interference effect between domains of differing lattice parameter in the top and bottom of the thin foil. We believe that these methods of image analysis could be usefully applied to the many thousands of HRTEM images that have been collected by other workers in the high temperature superconductor field. This work provides direct structural evidence for phase separation in high Tc cuprates, and gives support to recent stripes models that have been proposed to explain various angle resolved photoelectron spectroscopy and nuclear magnetic resonance data. We believe that the structural variation is a response to an opening of an electronic solubility gap where holes are not uniformly distributed in the material but are confined to metallic stripes. Optimum doping may occur as a consequence of the diffuse boundaries between stripes which arise from spinodal decomposition. Theoretical ideas about the high Tc cuprates which treat the cuprates as homogeneous may need to be modified in order to take account of this type of structural variation.

RESUMEN

BACKGROUND: Because of its advantages, topical cyclopentolate is often preferred over the gold standard, atropine. The purpose of the study was to obtain an overview over current cycloplegia protocols and to estimate the likelihood of severe complications due to the use of cycloplegics. METHODS: A questionnaire was sent to 107 German-speaking centres with a supposed high cycloplegia frequency. RESULTS: 57 centres answered, whereby 1,112 cumulated years of experience with cycloplegia were available for analysis. The frequency of cycloplegias varied between 2 and 180/week/centre, median 25/week/centre. A cumulated amount of 1.7 million cycloplegias was computed. The average extrapolated experience with cycloplegia was 49,000 cycloplegias/30 years. Severe complications which would cause a medical follow up of several hours or which led to a follow up in a ward were named 47 times and 2 times, respectively. CONCLUSIONS: During 30 years of a cycloplegia career with an average of 34 cycloplegias/week, one may expect 2-10 severe complications. In current practice, the patient risk of severe complications is very small. Health care professionals and parents should be informed about the frequent occurrence of light side effects in order to reach a good compliance with cycloplegia.

Asunto(s)

RESUMEN

We report biogenic magnetite whiskers, with axial ratios of 6 : 1, elongated in the [1 1 1], [1 1 2] and [1 0 0] directions, resembling the magnetite whiskers detected in the Martian meteorite ALH84001 by Bradley et al., and interpreted by those authors as evidence of vapour-phase (abiogenic) growth. Magnetosomal whiskers with extended defects consistent with screw dislocations and magnetosomes resembling flattened twinned platelets, as well as other twinning phenomena and other structural defects, are also reported here. Magnetosomes with teardrop-shaped, cuboidal, irregular and jagged structures similar to those detected in ALH84001 by McKay et al., coprecipitation of magnetite possibly with amorphous calcium carbonate, coprecipitation of magnetite possibly with amorphous silica, the incorporation of titanium in volutin inclusions and disoriented arrays of magnetosomes are also described. These observations demonstrate that the structures of the magnetite particles in ALH84001, their spatial arrangement and coprecipitation with carbonates and proximity to silicates are consistent with being biogenic. Electron-beam-induced flash-melting of magnetosomes produced numerous screw dislocations in the [1 1 1], [1 0 0], and [1 1 0] lattice planes and induced fusion of platelets. From this, the lack of screw dislocations reported in the magnetite particles in ALH84001 (McKay et al., and Bradley et al.) indicates that they have a low-temperature origin.

Asunto(s)

RESUMEN

PURPOSE: The purpose of this study was to analyze the cost-effectiveness of orthoptic screening for amblyopia in kindergarten. METHODS: A decision-analytic model was used. In this model all kindergarten children in Germany aged 3 years were examined by an orthoptist. Children with positive screening results were referred to an ophthalmologist for diagnosis. The number of newly diagnosed cases of amblyopia, amblyogenic non-obvious strabismus and amblyogenic refractive errors was used as the measure of effectiveness. Direct costs were measured form a third-party payer perspective. Data for model parameters were obtained from the literature and from own measurements in kindergartens. A base analysis was performed using median parameter values. The influence of uncertain parameters was tested in sensitivity analyses. RESULTS: According to the base analysis, the cost of one orthoptic screening test was 7.87 euro. One ophthalmologic examination cost 36.40 euro. The total cost of the screening program in all kindergartens was 3.1 million euro. A total of 4,261 new cases would be detected. The cost-effectiveness ratio was 727 euro per case detected. Sensitivity analysis showed considerable influence of the prevalence rate of target conditions and of the specificity of the orthopic examination on the cost-effectiveness ratio. CONCLUSIONS: This analysis provides information which is useful for discussion about the implementation of orthoptic screening and for planning a field study.

Asunto(s)

RESUMEN

INTRODUCTION: Because of its advantages, topical cyclopentolate is often preferred over the gold standard, atropine. The purpose of this study was to obtain an overview over current cycloplegia protocols and to estimate the likelihood of severe complications due to the use of cycloplegics. METHODS: A questionnaire was sent to 107 German-speaking centers with a supposed high frequency of cycloplegias. RESULTS: 57 centers answered, whereby 1,112 cumulated years of experience with cycloplegia were available for analysis. The frequency of cycloplegias varied between 2 and 180/week/center, median 25/week/center. A cumulated total of 1.7 million cycloplegias was computed. The extrapolated average experience with cycloplegia was 49,000 cycloplegias/30 years. Complications which would warrant a medical follow-up of several hours (severe complications) or which led to a follow-up in a ward (very severe complications) were named 47 times and 2 times, respectively. DISCUSSION: During 30 years of a cycloplegia career with an average of 34 cycloplegias/week, one may expect 2-10 severe or very severe complications. In current practice, the patient risk of severe complications is very small. Health care professionals and parents should be informed about the frequent occurrence of harmless side effects in order to achieve a good compliance with cycloplegia.

Asunto(s)

RESUMEN

A variety of adhesive support-films were tested for their ability to adhere various biological specimens for transmission electron microscopy. Support films primed with 3-amino-propyl triethoxy silane (APTES), poly-L-lysine, carbon and ultraviolet-B (UV-B)-irradiated carbon were tested for their ability to adhere a variety of biological specimens including axenic cultures of Bacillus subtilis and Escherichia coli and wild-type magnetotactic bacteria. The effects of UV-B irradiation on the support film in the presence of air and electrostatic charge on primer deposition were tested and the stability of adhered specimens on various surfaces was also compared. APTES-primed UV-B-irradiated Pioloform was consistently the best adhesive, especially for large cells, and when adhered specimens were UV-B irradiated they became remarkably stable under an electron beam. This assisted the acquisition of in situ phase-contrast lattice images from a variety of biominerals in magnetotactic bacteria, in particular metastable greigite magnetosomes. Washing tests indicated that specimens adhering to APTES-primed UV-B-irradiated Pioloform were covalently coupled. The electron beam stability was hypothesised to be the result of mechanical strengthening of the specimen and support film and the reduced electrical resistance in the specimen and support film due to their polymerization and covalent coupling.

Asunto(s)

RESUMEN

PURPOSE: Orthoptic screening in the kindergarten is one option to improve early detection of amblyopia in children aged 3 years. The purpose of this study was to analyse the cost-effectiveness of such a screening programme in Germany. METHODS: Based on data from the literature and own experience gained from orthoptic screening in kindergarten a decision-analytic model was developed. According to the model, all children in kindergarten, aged 3 years, who had not been treated for amblyopia before, were subjected to an orthoptic examination. Non-cooperative children were reexamined in kindergarten after one year. Children with positive test results were examined by an ophthalmologist for diagnosis. Effects were measured by the number of newly diagnosed cases of amblyopia, non-obvious strabismus and amblyogenic refractive errors. Direct costs were estimated from a third-party payer perspective. The influence of uncertain model parameters was tested by sensitivity analysis. RESULTS: In the base analysis the cost per orthoptic screening test was DM 15.39. Examination by an ophthalmologist cost DM 71.20. The total cost of the screening programme in all German kindergartens was DM 6.1 million. With a 1.5% age-specific prevalence of undiagnosed cases, a sensitivity of 95% and a specificity of 98%, a total of 4,261 new cases would be detected. The cost-effectiveness ratio was DM 1,421 per case detected. Sensitivity analysis showed considerable influence of prevalence and specificity on the cost-effectiveness ratio. It was more cost-effective to re-screen non-cooperative children in kindergarten than to have them examined by an ophthalmologist straight-away. CONCLUSIONS: The decision-analytic model showed stable results which may serve as a basis for discussion on the implementation of orthoptic screening and for planning a field study.

Asunto(s)

RESUMEN

BACKGROUND: The use of prisms and cover is the established clinical method to measure eye alignment, the accuracy of which may reach 0.5 degree (1 cm/m). By contrast, there are contradictory recommendations in the literature regarding the measurement with corneal reflections. The purpose of the study was to present a synopsis of the foundations on which such measurements are based, and to derive parameters for the measurement of eye alignment. MATERIALS AND METHODS: Simple eye models for an adult average eye were derived. From these the dependence of the shift of the corneal reflex and of the limbus upon eye rotation was derived and expressed as rotation versus shift ratio WF, in degrees per millimeter or prism diopters per mm. RESULTS: This study confirmed the findings of a number of studies in that the frequently quoted Hirschberg ratio of 7-8 degrees/mm (13 cm/m/mm) is much too low. The correct ratio is 12 degrees/mm (21 cm/m/mm). CONCLUSIONS: Without covering, a misalignment is estimated best by judging the difference between the positions of the corneal reflexes in both eyes. Due to the limited accuracy of this test of at best +/- 5 degrees (8.7 cm/m), pseudotropia may not be distinguished from microtropia. The magnitude of a refixation movement may be estimated best by looking at the limbus shift, with a ratio of about 5 degrees/mm (8.7 cm/m/mm).

Asunto(s)

RESUMEN

BACKGROUND: Objective, linear strabismometric methods are used preferentially to assess the eye alignment in patients with bad eyesight or with a deeply amblyopic eye, and also in uncooperative subjects, for instance children. The common point of these methods is that a distance must be measured or estimated, from which the eye rotation, or alignment, is computed through a conversion factor, the angular ratio. Such a ratio was introduced by Hirschberg in the 19th century. The purpose of the study was to examine the influence of the size of angular ratios and examiners influence upon the accuracy of estimation of eye alignment from the limbus position. METHODS: As an experimental test, 9 trained examiners estimated the amount of refixation movements between 0.5 degree and 26 degrees (1 cm/m and 48.8 cm/m). These refixation movements were simulated by a test person who executed fixation saccades in front of a tangent scale designed for a distance of 2.5 m. RESULTS: The magnitude of a refixation movement was estimated best by looking at the limbus shift, with a ratio of about 5 degrees/mm (8.7 cm/m/mm), and an accuracy of +/- 2 degrees (3.5 cm/m) (95% confidence interval) was reached for refixation movements up to +/- 5 degrees (8.7 cm/m). The threshold for detection of microtropia reached about 0.5 degree (1 cm/m). Accuracy was limited by two factors: the difference between the individual and average angular ratio, and estimating errors. CONCLUSIONS: Experienced examiners estimate the angle of strabismus from the magnitude of refixation movements up to +/- 5 degrees (8.7 cm/m) almost as accurately as with the prism and cover test.

Asunto(s)

RESUMEN

BACKGROUND: POEMS occurs only in about 1% of plasmocytoma cases, but in more than 50% of the rare osteosclerotic subtypes and plasma cell dyscrasias. The estimated frequency is 20 cases per year in Germany. Swelling of the optic disks is an early sign of the syndrome. CASE REPORT: An osteosclerotic plasmocytoma type IgA lambda was known in a 63-year-old farmer for 4 years. The primary lesion in the left femur was irradiated at diagnosis. Half a year prior to our examination the patient experienced edema of the legs and recurrent diarrhea. A staging confirmed the earlier diagnosis of a POEMS syndrome. The patient was presented for ophthalmologic examination because of optic disk swelling and progressive visual field defects: raster perimetry revealed enlarged blind spots and increased thresholds. Neurologic examination revealed polyradiculitis, increased protein levels in the cerebrospinal fluid and intracranial hypertension. The patient was treated with oral steroids which entailed improvement of the visual fields and decrease of optic disk swelling. CONCLUSIONS: Ophthalmologists play an active role in the staging, in the ruling out of other causes, and in the treatment. Symptomatic treatment with oral steroids should be monitored with visual acuity, raster perimetry and fundus examinations.

Asunto(s)

RESUMEN

BACKGROUND: The purpose of the study was to investigate the computer aided screening method using Purkinje image I and IV reflection patterns for the detection of inapparent eye misalignment and to compare this to an orthoptic examination. MATERIALS AND METHODS: 590 subjects up to 72 months of age with inapparent eye misalignment were recruited from the orthoptic outpatient department and externally. The computer aided screening consisted of taking a series of still video pictures with Purkinje reflection patterns. These were evaluated in an examiner independent way to reach a recommendation whether the child needed an ophthalmological referral or not. As gold standard, an orthoptic examination was performed. For analysis, the data were split by age groups. The orthoptic results were tested for certainty and repeatability. RESULTS: The computer aided examination had the highest sensitivity of 0.82 in the age group up to 2.5 years of age, and a specificity of 0.90. With an estimated prevalence for microtropia of 0.01, the extrapolated positive predictive value was 0.08, and the negative predictive value was 0.998. In the age group up to 2.5 years of age, the percentage of orthoptic examinations without clear result (neither non-referral, nor strabismic) was 22.4%, and 6.1% in the screening examination. Among the cases which were examined repeatedly, some were classified as "strabismic" in the beginning, and as "non-referral" in the end in the orthoptic examinations. CONCLUSIONS: The examiner independent, computer aided screening method is a cost effective option for the screening for inapparent eye misalignment, especially in the age group up to 2.5 years of age. If an orthoptic examination was carried out for screening, one should expect a higher rate of false positives, which entails more costly ophthalmological checks. Future studies should assess the validity of the single ortoptic examination as the gold standard in this age group.

Asunto(s)

RESUMEN

BACKGROUND: The alternating prism and cover test is the conventional test for the measurement of the angle of strabismus. The error induced by the prismatic effect of glasses is typically about 27-30%/10 D. Alternatively, the angle of strabismus can be measured with methods based on Purkinje reflex positions. This study examines the differences between three such options, taking into account the influence of glasses. MATERIALS AND METHODS: The studied system comprised the eyes with or without glasses, a fixation object and a device for recording the eye position: in the case of the alternate prism and cover test, a prism bar was required; in the case of a Purkinje reflex based device, light sources for generation of reflexes and a camera for the documentation of the reflex positions were used. Measurements performed on model eyes and computer ray traces were used to analyze and compare the options. RESULTS: When a single corneal reflex is used, the misalignment of the corneal axis can be measured; the error in this measurement due to the prismatic effect of glasses was 7.6%/10 D, the smallest found in this study. The individual Hirschberg ratio can be determined by monocular measurements in three gaze directions. CONCLUSIONS: The angle of strabismus can be measured with Purkinje reflex based methods if the fundamental differences between these methods and the alternate prism and cover test, and if the influence of glasses and other sources of error are accounted for.

Asunto(s)

RESUMEN

BACKGROUND AND PURPOSE: In Germany, 750,000 children are born per year who should be screened for developmental visual defects in the age range 24-48 months. However, the established pediatric screening program is not sufficient to prevent amblyopia. The purpose of this study was to examine the cost-effectiveness of alternatives for amblyopia and microtropia screening. METHODS: Three options were compared: (1) an orthoptic screening carried out in the field, for instance in kindergartens, (2) an examiner-independent objective apparatus-based screening, and (3) a complete ophthalmological and strabismological examination carried out in a practice. The costs of screening, follow-up examinations and of the treatment were modelled for prevalences of 1% (microtropia) and 5% (amblyopia). The benefit due to treatment was calculated as the result of an avoided whole-person impairment of 3% and 1%. The income related, increased tax and health care payments were used to cover the costs. RESULTS AND CONCLUSIONS: In options (1) and (2) there were favorable cost-effective ratios. The practice-based option 3 was economically less promising. The higher the prevalence was, the higher the resulting cost-effectiveness.

Asunto(s)