Mathematical modelling of epidemics under specific regard of adenoviral keratoconjunctivitis.

At first ADV is presented as a typical pandemic. The contagiosity of adenovirus is high because of the viability of the virus on inorganic surfaces in medical offices up to 35 days. Outbreaks and epidemics occur 3-30 days after infection, which is mainly contracted from medical facilities. EKC is considered a notifiable condition in most countries, and outbreaks, suspects and infections must be reported. Symptoms like "pink eye", foreign body sensations, photophobia, pain, signs such as follicles, hemorrhages and corneal infiltrates, and vision decrease associated with malaise are frequently observed first in one eye, later involving the fellow eye. Unilateral disease has a high rate of misdiagnosis. Currently no vaccine or virustatic is available, which is effective, cost-efficient and tolerable. Treatment is symptomatic and antiinflammatory. Late scarring may be amenable to phototherapeutic keratectomy. Infection control measures focus on the disinfection of equipment and hands of staff, the handling of infected patients with gloves, spatial separation of infected individuals resp. cohorting of infected patients, use of unit-dose eye solutions, and the chlorination of pools by approved and registered disinfectants and germicides. In connection with this it is shown how to handle the dynamics of infections by mathematical models like cellular automation, systems of differential equations and to visualize periodic effects by Fourier Analysis and to calculate costs by mathematical programming. Using mathematical analysis the percentage of a population needing vaccination to prevent spreading of pandemic can be calculated. It is shown here that especially the method of cellular automation is a simple way to simulate complex epidemiological situations without completely knowing the mathematical details.

[The history of optical signals for traffic regulation]. / Zur Geschichte der optischen Signalgebung im Verkehrswesen.

For signal transmission in traffic today, different optical, acoustic, or other physical or technical means are used for information. The different kinds of traffic (water navigation, road and rail, and, later air transport) made traffic regulation necessary early on. This regulation, from its very beginning in ancient times, began by means of optical signals; nowadays, this remains the most important method. From the very start, minimum requirements for the navigator's vision, color discrimination, dark adaptation, and even visual field were needed. For historical reasons, it was in seafaring medicine that these first developed. Besides the development of the different signals, methods for checking the requirements were soon developed. National and international requirements have been very different. Only within the last 50 years has international cooperation led to the acceptance of general standards for the different traffic modes. This article discusses the technical development of optical signals for the different kinds of traffic, from ancient times to the present, and explains the development of minimum requirements for the different visual functions.

Chromosome gain and loss in paraffin sections from malignant melanomas of the skin.

Alphoid DNA probes specific for the chromosomes #6, #7, #9, and #17 were used to screen interphase nuclei for numerical chromosome aberrations in histologic thin sections obtained from archival paraffin material of 25 human melanomas of different type, thickness and stage of progression. An alphoid probe for chromosome #3 was applied in four of these tumors. Besides a general large variation of the number of subpopulations of cells characterized by gains and losses of the studied chromosomes, there was a trend to higher variability in metastatic melanomas as compared to small (<1.5 mm thickness) non-metastatic ones and, particularly, to normal skin tissue. Chromosomes #6 and #9 were those often affected by loss in thick melanomas (>2 mm), while subpopulations showing a gain of these chromosomes, and, in addition, of chromosome #7 seemed more frequently to be associated with thin and non-metastatic ones. The frequency of cases showing gain of chromosome #17 clearly exceeded those with loss of this chromosome in the studied melanomas, but was most pronounced in thicker metastatic tumors.

Differentiation between Spitz nevi and malignant melanomas by interphase fluorescence in situ hybridization.

Spitz nevi are benign melanocytic neoplasias which have distinct pathological features that make the pathological differential diagnosis from malignant melanomas extremely difficult. The Spitz nevi may be misdiagnosed as malignant melanoma and vice versa. Therefore, interphase fluorescence in situ hybridization (I-FISH) was used for a possible discrimination between Spitz nevi and malignant melanomas on the basis of numerical aberrations of the chromosome complement in interphase nuclei of thin sections. Previous studies had shown changes in malignant melanomas which were not found at the same level in normal tissue or benign tumors. Thin sections of archival paraffin material from 42 Spitz nevi with different histological type and grade of anomaly were subjected to FISH-analyses using commercially available biotinylated and/or digoxigenated alphoid DNA probes of chromosomes 1, 6, 7, 9, 17 and 18, which were applied in combinations in a two- or three-color-FISH. Unaffected epithelial areas from the same sections served as. The obtained data were compared with those collected previously from thin sections of malignant melanomas prepared in the same way. Due to the sometimes limited nevus area investigated, the number of evaluable nuclei was lower than expected from previous experiences with malignant melanomas. Therefore, only 20 nevi could be reliably evaluated. The comparison of the group of Spitz nevi with the group of controls did not show any significant difference regarding chromosomes 1, 6, 7, 9 and 17 (Wilcoxon test). The method used to detect chromosomal loss or gain in the individual Spitz nevi demonstrated only two nevi (one of the spindle cell type with a low to middle grade of anomaly, the other of the epitheloid cell type with a middle grade of anomaly) with a gain of chromosome 7 and chromosome 17, respectively. So, with respect to the histological type and grade of anomaly, no numerical aberrations could be detected in Spitz nevi. The comparison of the group of Spitz nevi with subgroups of malignant melanomas (metastatic, non-metastatic, melanomas with a thickness <1.5 mm and melanomas with a thickness >2. 0 mm) and with the whole group of malignant melanomas showed significant differences concerning chromosome 9 (Mann-Whitney U test), signal indices, which were higher in the melanomas than in the Spitz nevi. Regarding chromosomes 6, 7 and 17 no significant differences could be shown, although a trend of gain in melanomas and of loss in Spitz nevi was observed of these chromosomes.

Mechanical stability of the cornea after radial keratotomy and photorefractive keratectomy.

BACKGROUND: Corneal refractive surgical procedures alter the shape and structure of the tissue, possibly compromising its mechanical stability. METHODS: One or both eyes of 87 subjects were studied: 26 of these 87 had been treated for myopia by excimer laser ablation and 36 by radial keratotomy; 25 without previous corneal surgery functioned as controls. Corneal topography was evaluated by TMS-1 videophotokeratography before and after 180 degrees tilting of the patient, and the pressure-induced ring-wise changes in spherical equivalent power (axial power) were calculated. Changes in corneal shape also were evaluated by computing the instantaneous radius of curvature. The intraocular pressure was measured before and after tilting by a hand-held applanation tonometer. RESULTS: The mean intraocular pressure increased from 13.9 +/- 2.3 mm Hg before tilting to 30.0 +/- 3.8 mm Hg during tilting. In the control eyes, the mean power of the central cornea during tilting decreased 0.187 +/- 0.045 diopters (D) (p < .05); in the excimer-laser-ablated eyes, 0.038 +/- 0.056 D (not statistically significant); and in those treated with radial keratotomy, 0.523 +/- 0.054 D (p < .01). After radial keratotomy, the cornea steepened outside the clear zone in response to pressure loading, whereas it did not change significantly in the laser-ablated or control eyes. CONCLUSIONS: Pressure-induced deformation of normal and excimer laser-ablated human cornea is small, whereas radially incised corneas have significantly decreased mechanical stability.

The corneal endothelium as a standard for the assessment of complications in microsurgery.

Endothelial cell morphology is an important parameter for the quality control of different surgical techniques, especially in the anterior segment. The minimizing effect of hyaluronic acid in implant surgery can be demonstrated by the decrease of endothelial cell loss as compared to standard techniques. Besides, we can show that the implantation of artificial lenses into the capsular bag is less traumatizing to the cornea than anterior chamber lenses. Other factors to control the surgical techniques are the keratoplastics, especially modified to different trephination techniques and last but not least YAG laser surgery of the cataract membranes. In the latter, there is a direct correlation between endothelial trauma and distance of focus and total energy. Even in isolated cases we can draw conclusions from endothelial morphology to intra-postoperative complications. New surgical techniques which could lead to damage of the cornea should be tested by endothelial cell analysis.

Vacuum fixation of corneal lenticules for refractive surgery.

Using the rotating lamellar keratome, a simplified method for nonfreeze shaping of corneal tissue was developed. A set of refractive molding forms was designed for a standardized lenticule diameter. The fixation of the lenticule was achieved by a system of suction holes. A mechanical fixation ring was not required, as the total shearing force exerted by the rotating blade is neutralized even by a low suction setting. Different surface properties (polished, matt, rough) were compared, showing an influence of the surface structure on friction and thus lenticule fixation. With our optimized molding form, the lenticule is safely retained at a suction of 2.5 m H2O.

Measurement of elastic resisting forces of intraocular haptic loops of varying geometrical designs and material composition.

The relationship between experimentally induced intraocular lens (IOL) haptic deformation and resulting elastic haptic counter-resisting forces measured by electronic dynamometry was examined for 34 different IOL haptics of varying material composition and geometrical designs. Poly(methyl methacrylate) (PMMA) and polypropylene loops of similar geometry did not fundamentally differ from one another, although lenses of differing geometry behaved differently. Unlike PMMA and polypropylene loops, soft haptics of poly-HEMA and silicone rubber demonstrated a larger elastic resistance force to the same degree of deformation. This was based upon design characteristics of the lenses and not upon intrinsic properties of the materials, which would have produced the opposite result. By comparative analysis of these dynamometer measurements and considerations of the lens design and elastic properties (including memory) of the component materials, we can calculate the stresses upon the zonular and capsular bag structures during and after IOL implantation.

The problem of truth in psychotherapy: a phenomenological approach to treatment.

Scientific method cannot establish whether a patient's productions in psychotherapy are truthful because of the nature of Cartesian dualism. Phenomenology, however, is an alternative that clarifies what is truthful in therapy and provides insight into the process of therapeutic change itself. Basic ideas of Paul Ricoeur and the epistemology of Michael Polanyi are applied to the treatment setting to evaluate change. Clinical examples illustrate the usefulness of exegesis as a paradigm for understanding the process of therapy.

Vital staining of corneal endothelium.

The efficacy and applicability of dual vital staining of human and porcine corneal endothelium with trypan blue and alizarin red S stains was investigated. Exposure of endothelial cells to different concentrations of these two dyes for varying periods of time revealed that 0.3% solution of trypan blue for 1 minute followed by 0.2% solution of alizarin red S (pH 4.2) for 1/2 to 1 minute was the most useful technique to assess the cell viability, micro to macro damage, cell division and cell counts, etc. Alizarin red S dye should not be used in in vivo evaluation, while trypan blue was very effective to evaluate the endothelial viability of donor cornea just prior to keratoplasty.

Continuous assessment of intraocular pressure - telematic transmission, even under flight- or space mission conditions.

Fluid shift after entering into microgravity, but also under equivalent flight conditions leads to enormous increase of intraocular pressure. To assess this precisely position - and gravity independent, handsome, automatic tonometers have been developed (German-Spacelab D1-Mission, German-Spacelab D2-Mission, German-Russian-MIR-Mission) telemetric transmission of measuring results of course would find scientific but also functional interest. The same is true for recently designed automatic intraocular pressure sensors, registering intraocular pressure continuously, day and night. Also recently designed new automatic ophthalmodynamometer, allowing directly to assess the intracranial pressure, but also perfusion pressure within the eye also could benefit from a direct telemetric transmission. New technical solutions allowing for the first time even telematic data transmission, are reported.

[Refractive surgery and flight safety]. / Refraktive Chirurgie und Flugsicherheit.

For both VFR and as IFR flight, visual assessment is the major source of information for the pilot. The new possibilities for change of refraction by means of corneal refractive surgery have led to an increasing demand from pilots for these new methods. Can these methods successfully be applied for aviation purposes? The valid regulations for medical standards of pilots, as well as the future international regulations such as JAR and ICAO, are explained in this respect. A report is given on the work of the Advisory Board of the German Federal Government Air Traffic Authority and on the cases treated so far and their outcome, and recommendations are expressed. Concerning the legal situation and clinical experience, advice for pilots, aviation medical examiners and ophthalmologists is given.

[Revisions in the assessment of fitness for aircraft flying]. / Neuerungen in der Beurteilung der Luftfahrttauglichkeit.

So far medical requirements for aviators have been defined by national licensing authorities. For a long while ophthalmological problems, insufficiencies in vision, refraction or color vision, have been responsible for approximately 50% of rejection of applicants for medical reasons. New international regulations proposed as well by ICAO as JAA try to lead to a new balance in these requirements. In general, ophthalmological requirements now allow for lower standards, specifically in refraction, but also in color vision. Also new examination methods are admitted. German and French authorities have announced their opposition being concerned about flight safety for the future.

[New diagnostic possibilities by a fully automatic applanation tonometer for the ophthalmologist. From the Goldmann principle to automated tonometry]. / Neue diagnostische Möglichkeiten durch ein vollautomatisches Applanationstonometer für den Augenarzt. Vom Goldmann-Prinzip zur automatischen Tonometrie.

Applanation tonometry, following Goldmann's hypothesis serves as the gold Standard in tonometry. However, even this approach principle does not always eliminate examiner's error, especially in defining the applanation surface. An automatic surface and force control system is used to increase measurement precision, thus increasing precision and speed of measurement. The instrument, already in use for the patient's self-tonometry, is now also available for the ophthalmologist. An additional coaxial observation system allows precise centering of the applanation surface onto the cornea. This allows new applications of applanation tonometry in daily routine.

[Aviation and space flight ophthalmology]. / Luft- und Raumfahrtophthalmologie.

So far it has not been possible to adapt man genetically to the specific environmental conditions of flying. A variety of disturbing factors act on the human body and affect its vital as well as sensory functions, vision being considered the most important sense for providing information. The effects of oxygen deficiency caused by increasing altitude, acceleration and centrifugal force affecting visual function, ocular motility, and pupillary reactions are well known. Like visual illusions, vibrations, high accelerative forces, high illuminance and glare at high altitudes impair the visual perception of the environment. In space flight further problems ensue from weightlessness and short-wave radiation. The high medical standards that must be met by the eyes of flying personnel, as will as for air-traffic controllers, result in the enhancement of flight safety. After operations on the cornea or retina or cataract operations in pilote, the retinal findings and DOP must be monitored closely. Special attention must be paid to means of visual aids, corrective lenses, contact lenses, and intraocular lenses. Ophthalmology is a very important element of aviation and aerospace medicine.

[Effect of corneal hydration and dehydration of donor tissue on the precision of the thickness in lamellar refractive keratoplasty]. / Einfluss der Hornhautquellung und Entquellung des Spendergewebes auf die Dickenpräzision bei der lamellären refraktiven Keratoplastik.

The influence of corneal hydration on the precision of plano lamellas and on the precision of lenticles modified with a "non-freeze" technique was studied in pig eyes. Ten pig eyes were dissected with a rotating lamellar microkeratome, and the discs were measured with a mechanical pachymeter. The hydration of the discs was measured in BSS and in dextran solution. A total of 160 corneal discs with different degrees of hydration were modified with a "non-freeze" technique on concave anf convex vacuum cylinders and measured with a photokeratoscope TMS. The discs increased in thickness within 3 h becoming 1.7 times as thick in BSS and 1.2 times as thick in dextran. After refractive dissection minor modifications were achieved with higher precision than were larger corrections. However, we achieved an undercorrection after all refractive dissections. Plano-discs for refractive modification should be taken from dehydrated corneoscleral discs or from intact eyes. Owing to mechanical factors during cutting and tissue hydration undercorrection of the intended change was observed.

[New aspects of surgical treatment of glaucoma. Comparison of viscoelastic substances in chamber angle surgery]. / Neue Aspekte in der operativen Behandlung des Glaukoms. Vergleich viskoelastischer Substanzen in der Kammerwinkelchirurgie.

The development of new viscoelastic substances opens up new perspectives for chamber angle surgery under direct view. The success of "Cyclodialysis ab interno" treating children with glaucoma is often reduced by scar formation of the cleft. Therefore four different viscoelastic substances were instilled during an animal experimental study into the cleft and compared in their effect. We used hyaluronic acid with different molecular weight (Healon and Healon GV) and cross-linked forms of hyaluronan as a fluid and a gel (Hylan fluid and Hylan gel). A cyclodialysis ab interno was performed on 14 eyes of cynomolgus monkeys. The functional results (tonometry, outflow facility, autoradiography) and the morphological findings will be presented and their consequences for an extended indication of the cyclodialysis ab interno will be discussed.

[2 years self-tonometry. Acceptance and results]. / 2 Jahre Selbsttonometrie. Akzeptanz und Ergebnisse.

For more than 2 years we have been trying out a microprocessor-controlled self-tonometer to determine its clinical usefulness. Most of the measurements were taken with two instruments (A and B). In vitro calibration series on human donor corneas gave good results over the whole pressure range. In a patient series both instruments were compared with the established hand-held applanation tonometer put out by Draeger (HAT). Each self-tonometer was applied three times, followed by a controlling measurement with the HAT. The correlation coefficient between instrument A and HAT was 0.85 with a standard deviation of +/- 1.9126 mmHg. Instrument B showed a better correlation (r = 0.904), the standard deviation was similar to tonometer A (SD = +/- 1.8598 mmHg). Most of the values obtained by the self-tonometers-about 50%-deviated from the corresponding HAT values by +/- 1 mmHg. The new measurement principle was accepted by 75% of all patients. Improvements in the details are planned in order to simplify tonometer handling and increase the accuracy and precision of the measurements.

[Precision of lenticular thickness in relation to full stroma corneal thickness. Experimental results with the lamellar microkeratome]. / Lentikeldickenpräzision in Abhängigkeit von den Gewebeausgangsdicken. Experimentelle Ergebnisse mit dem lamellären Mikrokeratom.

In this study 150 pig corneas and 20 human corneas were dissected with an automatic rotating microkeratome for lamellar grafting. The cornea thickness varied between 0.507 mm and 0.829 with an average 0.66 mm. The aim of this investigation was to show the influence of corneal thickness, the chosen diameter and spacing on the precision of cutting lenticles. We did ten series: the pig corneas were dissected at three different intervals of 0.15, 0.25, 0.35 mm and diameters of 9 and 6mm. The human corneas were cut at intervals of 0.4 mm and 0.25 mm and with diameter of 9 and 7 mm. Although the pig corneas were fresh, the intraocular pressure was too low. It was raised with an injection of physiological salt solution to a predefined level. The rotating speed of the trephine blade, the speed of blade advancement and lubrication fluid were kept constant. Ultrasound pachymetry was performed on the center of the corneas before cutting had on the lenticles afterward. We showed that a thick corneal diameter had a negative influence, i.e., the greater the diameter, the lesser the precision; the same was true for the corneal thickness. On the other hand, the intervals had just the opposite effect: the closer they were, the better the correlation. The human eye results were different in quantity but not in tendency, with less striking effects. The average variation for pig corneas was 22% and for human eyes 8%. The best results were received with a large interval, a small diameter, and a normal corneal thickness in human eyes.

[Optimizing the automatic self-tonometer by an acoustic control signal and changed fixation optics]. / Optimierung des automatischen Selbsttonometers durch ein akustisches Kontrollsignal und eine veränderte Fixieroptik.

An automatic self-tonometer must fulfill special requirements from the point of view of precision as well as user-friendliness. The sensor that applanates the cornea must be perfectly centered on the vertex in order to measure the intraocular pressure correctly. The modified version of the self-tonometer has been equipped with an acoustic control signal and a modified fixation lamp that facilitate its use. In order to analyze the effectiveness of these hardware changes, we compared the modified tonometer to the existing self-tonometer in a randomized study with 30 patients. Reference was the Draeger hand-held applanation tonometer. The results show comparable precision; however, the percentage of error measurements in the modified tonometer was considerably lower. This is a definite improvement in the development of the self-tonometer.