[New DIN and ISO norms for determination of visual acuity]. / Neue DIN- und ISO-Normen zur Sehschärfebestimmung.

Recently, three international norms (ISO) for visual acuity assessment were revised. The DIN EN ISO 8596:2018 stipulates the Landolt C eye chart as the standard optotype and specifies display characteristics. An informative annex lists clinical optotypes for the first time. These include the ETDRS chart, Snellen chart and pediatric optotypes; however, these clinical optotypes do not have the same status as the Landolt C chart, since even with identical font size and stroke width they may differ in recognizability. The technical report ISO/TR 19498:2015 complements DIN EN ISO 8596. A scientifically appropriate procedure is described, which enables a quantitative correlation of clinical optotypes with the Landolt C chart. The DIN EN ISO 10938:2016 describes the required optical quality of optotypes. For the first time, electronic devices are explicitly approved for standardized visual acuity tests. Consequently, according to this amendment electronic devices may be used for acuity assessment for ophthalmological expert opinions according to DIN 58220, part 3.

[Analysis of spectacle lens prescriptions shows no increase of myopia in Germany from 2000 to 2015]. / Analyse der Brillenstärken zeigt keine Zunahme der Myopie in Deutschland von 2000 bis 2015.

OBJECTIVE: To determine whether the prevalence and magnitude of myopia among children and young adults wearing spectacles has increased in Germany from 2000 to 2015. MATERIAL AND METHODS: A total of 1,223,410 refraction values from 278,432 male and 333,273 female subjects between 5 and 30 years of age were analyzed. All subjects had received a new pair of spectacles between 1 January 2000 and 31 December 2015. The parameter studied was the spherical equivalent averaged over both eyes of each subject (N = 611,705). In order to identify temporal changes, the entire period of 16 years was divided into 4 time intervals of 4 years each. In the subjects three evaluation criteria were studied as a function of age: a) the frequency of myopic subjects among all spectacle wearers, b) the mean spherical equivalent and c) the distribution of the individual spherical equivalents. RESULTS: a) The frequency of myopic corrections among all spectacle wearers did not increase from 2000 to 2015. At 5 years of age, 9% of all children wearing glasses were myopic (≤-0.5 D) and 80% were hyperopic (≥+0.5 D). At the age of 10, 20 and 25 years, 46%, 75% and 79%, respectively, of all spectacle wearers were myopic and 42%, 13% and 10% hyperopic. b) The mean spherical equivalent, averaged across all spectacle wearers of the same age, did not show a myopic shift from 2000 to 2015. At the age of 5, 10.3 and 27 years, the mean spherical equivalent all subjects wearing glasses was +1.74 D, 0.0 D and -1.91D. c) The refractive power distribution of the individual spherical equivalents did not change significantly from 2000 to 2015. Neither low nor high myopias were more abundant in the period 2012-2015 compared to the previous years. CONCLUSION: The frequency and the refractive power of myopia did not increase in Germany over the last 16 years.

[Contrast vision-definitions, conversions, and equivalence tables]. / Kontrastsehen ­ Definitionen, Umrechnungen und Äquivalenztabelle.

Human contrast vision and its quantitative assessment are gaining more attention. Publications on this topic can be confusing due to the overabundance of differing definitions and quantification of contrast vision. As a case in point, in Germany, contrast ratios as required for certain driving licenses and the DIN-defined contrast ratio are reciprocal. In this article, the five most important definitions of luminance contrast and contrast vision (Michelson, Weber, contrast ratios, logCS) are presented. We detail the specific domains for them, give formulae to convert between all of them and provide a table with equivalent values. We recommend the unit logCS wherever possible.

[New DIN norms for determination of visual acuity]. / Neue DIN-Normen zur Sehschärfebestimmung.

In 2009 the DIN 58220 norms for determination of visual acuity were revised. The new rules came into force on 1(st) November 2009. The new regulations on expert assessment of visual acuity (DIN norm 58220, part 3) are particularly important for ophthalmologists because as a result of the revisions the approach to testing visual acuity in patients with low acuity must be changed in the future. The background and potential problems will be presented and a simple solution for the lower acuity range will be suggested. Parts 5 (general test of vision) and 6 (driving-related vision test) of DIN 58220 remain practically unchanged. Part 7 of DIN 58220 is newly introduced, in which regulations for testing mesopic contrast vision with and without glare are defined for the first time.

[Photopic contrast sensitivity. Local contrast perception]. / Photopisches Kontrastsehen. Ortliche Kontrastempfindlichkeit.

Contrast perception is an important visual function. Contrast sensitivity (CS) is affected by to optical reasons (aberrations, scatter, diffraction) or neural dysfunction (e.g., glaucoma, optic nerve diseases). In clinical practice the measurement of CS is relevant for disease monitoring, expert opinions, roadworthiness assessment, and recruitment screening. Furthermore, CS testing is often required in studies assessing optical quality, e.g., cataract or refractive surgery. Adding an appropriate glare source allows measurement of the glare-induced loss of CS (disability glare). Compared to high-contrast acuity, CS is more variable and strongly depends on the type of test, illumination, test strategy, and contrast definition; ceiling effects are quite common among many tests. Maximal standardization is important, especially for follow-up exams. In summary, CS testing cannot be regarded as a routine test. The present report by the DOG commission for quality management of psychophysical assessment covers the physiological background, testing principles, and strategies and presents a tabular overview of common tests.

[Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS). A new test to determine contrast sensitivity under variable ambient and glare luminance levels]. / Das "Frankfurt-Freiburg Contrast and Acuity Test System" (FF-CATS). Ein neuer Test zur Kontrastsensitivitätsbestimmung unter variablen Beleuchtungs- und Blendbedingungen.

BACKGROUND: The purpose of the present study was to evaluate a computerized test for measurement of contrast sensitivity thresholds under variable ambient and glare luminance levels. METHODS: A total of 40 eyes of 40 healthy subjects were examined with the FF-CATS and the Functional Acuity Contrast Test (FACT) at 0.167 cd/m(-2) (mesopic) and 167 cd/m(-2) (photopic). Measurements were performed twice with and without glare in a randomized fashion. Tests were evaluated according to three criteria: (1) repeatability, (2) discriminative ability, and (3) validity. RESULTS: The FF-CATS showed a higher discriminative ability between the two groups compared to the FACT charts. Under photopic conditions, the COR value was 0.39 for the FF-CATS and 0.26 for the FACT charts; under mesopic illumination, the COR value for the FF-CATS was 0.46 and 0.36 for the FACT charts. CONCLUSION: The FF-CATS is a reliable, sensitive, valid, and flexible test system for the determination of visual acuity and contrast sensitivity thresholds under variable ambient and glare luminance conditions.

[Optical and physiological limits of wavefront-controlled keratectomy]. / Optische und physiologische Grenzen der wellenfrontgesteuerten Hornhautchirurgie.

According to optical diffraction theory, a visual acuity of 20/3.5 is possible in human eyes with pupil diameters larger than 6 mm. This theoretical value cannot be obtained in practice - in fact visual acuity is limited by the scale of the mosaic of the retinal cones. Anatomical data and the model by Helmholtz-Hering suggest that visual acuity of humans cannot be substantially higher than 20/10. Many young adult reach this visual acuity with their normal spectacles or contact lens correction. The human eye has higher-order aberrations which can be measured with a Hartmann-Shack aberrometer. A partial correction of these aberrations is possible by means of wavefront-controlled keratectomy and customized corneal ablation. A perfect eye completely free of ocular aberrations cannot be created by customized refractive surgery as, for example chromatic aberration cannot be corrected and the strength of ocular aberrations depends on the state of accomodation and varies with time.

Effect of lazaroid pretreatment on dopamine-induced impairment of the rat nigrostriatal system.

Oxidative stress induced by enhanced catecholamine metabolism may subsequently cause damages to the nervous system. We used in vivo-pulse voltammetry to study an enhanced brain dopamine (metabolism) induced either by intranigral dopamine (DA) injection or reduction of cerebral blood flow. One week after intranigral injection of 10 microg DA or unilateral occlusion of one carotid the DA activity in the ipsilateral striatum was decreased as compared to the contralateral side. Three weeks after DA application and carotid clamping the DA activity was restored to normal. The significant reduction of 3,4-dihydroxyphenylacetic acid (DOPAC) after one week was attenuated by pretreatment with the lazaroid U-74389G, injected 20 min before surgery. The results are in accordance with the view that radical mechanisms play a crucial role in the impairment of the nigrostriatal system induced by oligemia.

Alterations of host defence system after sleep deprivation are followed by impaired mood and psychosocial functioning.

In healthy humans, sleep deprivation (SD) has consistently been demonstrated to impair different parameters of the host defence system and of psychosocial functioning. However, the individual timing of these alterations and their possible association have remained unknown so far. We therefore investigated functional measures of the individual host defence system as well as of subjective well-being and psychosocial performance in 10 healthy male adults before and after SD, as well as after recovery sleep. In detail, we examined the number of leukocytes, granulocytes, monocytes, lymphocytes, B cells, T cells, T helper and cytotoxic T cells, natural killer (NK) cells as well as the interleukin-1 beta (IL-1 beta) release from platelets after serotonin (5-HT) stimulation. Mood and psychosocial performance (excitement, energy, ability to work and timidity) were measured by visual analogue scales. Taken together, SD induced a deterioration of both mood and ability to work, which was most prominent in the evening after SD, while the maximal alterations of the host defence system could be found twelve hours earlier, i.e., already in the morning following SD. Our findings therefore suggest an SD-induced alteration of these psychoimmune response patterns in healthy humans preceding deterioration of mood and psychosocial functioning.

Bromal-derived tetrahydro-beta-carbolines as neurotoxic agents: chemistry, impairment of the dopamine metabolism, and inhibitory effects on mitochondrial respiration.

The mammalian alkaloids tryptoline (1) and eleagnine (2) as well as the highly halogenated (X = F, Cl, Br) tetrahydro-beta-carbolines (THbetaCs) 3-5, structurally similar to the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 6), were found to have a common feature of inducing a severe impairment of the nigrostriatal dopamine metabolism and inhibiting complex I of the mitochondrial respiratory chain highly selectively. Within the series of compounds tested, 1-tribromomethyl-1,2,3,4-tetrahydro-beta-carboline ('TaBro', 5), which was prepared in high yields from the biogenic amine tryptamine ('Ta', 7) and the unnatural aldehyde bromal ('Bro', 8) by a Pictet-Spengler cyclization reaction, turned out to be the most potent toxin in vitro and in vivo. As demonstrated by voltammetric measurements on rats, for all the THbetaCs 1-5 investigated, intranigral application of a single dose of 10 microg resulted in a significant reduction of the dopaminergic activity in the striatum, with the strongest effect being observed for TaBro (5). Using rat brain homogenates, again 5 (IC50 = 200 microM) as well as its dehydrohalogenation product 11 (IC50 = 150 microM) exhibited the most pronounced inhibitory potential on mitochondrial respiration. The halogen-free THbetaCs 1 and 2 as well as the MPTP metabolite 1-methyl-4-phenylpyridinium ion (MPP+), by contrast, showed only a moderate inhibition at concentrations in the millimolar range (e.g. for MPP+: IC50 = 3.5 mM). For an elucidation of the role of hydrophobic portion in the inhibitory action against complex I activity, several N-acyl derivatives (15-21) of 5 were synthesized and tested. An X-ray diffraction study on the 3-dimensional structure of trifluoroacetylated highly halogenated THbetaCs (12-14) revealed the tetrahydropyrido part to adopt a nearly planarized half-chair conformation. Because of the steric demand of the trihalogenmethyl moiety (CF3 < CCl3 < CBr3), the N-substituent is dramatically pushed out of that ring 'plane'.

White blood cells and cortisol after sleep deprivation and recovery sleep in humans.

Sleep deprivation (SD) has enriched our treatment programme for major depression. SD has been demonstrated to modify different host defence activities. There is some evidence that there are reciprocal relationships between immune function and increased hypothalamic-pituitary-adrenocortical (HPA) axis activity in depression. We therefore investigated the number of leukocytes, granulocytes, monocytes, lymphocytes, B cells, T cells, helper T cells, cytotoxic T cells, NK cells and salivary cortisol in 10 healthy men before and after total SD (TSD) as well as after recovery sleep. Blood samples were drawn on 3 consecutive days at 7 am, 1 pm and 7 pm, respectively. Comparison of the 7 am values by contrast analysis yielded significant differences for granulocytes (p = 0.044) and NK cells (p = 0.001) after SD and recovery sleep. NK cells decreased and granulocytes increased after SD and after recovery sleep. Significant differences between single points in time across the day were found for granulocytes (p = 0.022), monocytes (p = 0.031), T cells (p = 0.005), helper T cells (p = 0.004), cytotoxic T cells (p = 0.005) and NK cells (p = 0.017). No significant difference could be detected for leukocytes, lymphocytes and B cells counts. These results favour the thesis that SD and recovery sleep lead to changes in the distribution of peripheral leukocytes, especially in a reduction of NK cells after SD and recovery sleep. The cortisol rhythm was affected neither by SD nor recovery sleep.

Platelet aggregation during abdominal surgery in an experimental pig model: the effects of presurgical antibiotic protocols and volume replacement with hydroxyethyl starch.

The effect of presurgical antibiotic protocols in combination with hemodilution on platelet aggregation was studied. Thirty pigs were randomly assigned to three groups. Group 1 received amoxicillin/clavulanic acid, group 2 metronidazole+cefuroxime, and group 3, as a control, sodium chloride. They underwent laparotomy, massive blood loss, and volume replacement with hydroxyethyl starch 200, followed by an anaphylactoid reaction. Platelet aggregation was measured by the turbidometric method. Neither antibiotic protocols had any effect on platelet aggregation as compared with the control group. In all three groups, aggregation to ADP and collagen was significantly reduced after volume replacement with hydroxyethyl starch. In contrast, the sensitivity to the aggregating effects of collagen was increased as assessed by a higher frequency of responses to low concentrations of collagen and a shortened latency of the aggregation response after collagen addition. Further in vitro studies revealed that dilution of plasma with hydroxyethyl starch specifically induced the changes seen after in vivo volume replacement. The results suggest that the plasma substitute hydroxyethyl starch 200 increases the sensitivity to low doses of collagen, an effect never described before and considered of clinical relevance.

Accuracy and accommodation capability of a handheld autorefractor.

PURPOSE: To determine the accuracy of measurement by the Nikon Retinomax handheld autorefractor and its ability to relax accommodation. SETTING: Pediatric Section, Department of Ophthalmology, University of Mainz, Germany. METHODS: To perform a series of comparative measurements, autorefractor readings were obtained on healthy young adults (students) and on children aged 2 to 12 years. The autorefractor readings were compared with subjective refractions of the young adults and with cycloplegic retinoscopy of the children. RESULTS: In adults, the accuracy of the handheld autorefractor measurements was comparable to that of conventional tabletop autorefractors. In children, the autorefractor measurements performed under cycloplegia were reliable; when cycloplegic agents were not administered, 24% were overcorrected by more than -2.0 diopters. CONCLUSION: Cycloplegia is often necessary to obtain accurate autorefractor results.

Electrophysiological correlates of vernier and relative motion mechanisms in human visual cortex.

Vernier onset/offset thresholds were measured both psychophysically and with the steady-state VEP by introducing a series of horizontal breaks in a vertical square-wave luminance grating. Several diagnostic tests indicated that the first harmonic component of the evoked response generated by periodic modulation of offset gratings taps mechanisms that encode the relative position of spatial features. In the first test, a first harmonic component was only found with targets that contained transitions between collinear and noncollinear states. VEP vernier onset/offset thresholds obtained with foveal viewing were in the range of 15-22 arc sec. Control experiments with transitions between symmetrical, noncollinear patterns (relative motion) did not produce first harmonic components, nor did full-field motion of a collinear grating. A second series of experiments showed that VEP thresholds based on the first harmonic component of the vernier onset/offset response had an eccentricity dependence that was very similar to that found in a psychophysical discrimination task that required a left/right position judgment (vernier acuity). Other recordings showed that the first harmonic of the vernier onset/offset VEP was degraded by the introduction of a gap between stimulus elements, as is the displacement threshold. The vernier onset/offset target also produced a second harmonic component that was virtually identical to the one produced by a relative motion stimulus. Displacement thresholds based on these second harmonic components showed a more gradual decline with retinal eccentricity than did the first harmonic component elicited by vernier offsets. The second harmonic of the vernier onset/offset VEP was relatively unaffected by the introduction of gaps between the stimulus elements. The first and second harmonic components of the vernier onset/offset VEP thus tap different mechanisms, both of which support displacement thresholds that are finer than the resolution limits set by the spacing of the photoreceptors (hyperacuity).

Iron accumulation in the substantia nigra in rats visualized by ultrasound.

In recent studies, we have found a marked increase in substantia nigra (SN) echogenicity in patients with Parkinson's disease (PD) using transcranial ultrasound. Because a substantial body of evidence has accumulated indicating a selective elevation of iron in the SN from patients with PD, we set out to test the hypothesis that trace metals like iron could lead to the observed increase of SN echogenicity in PD. Rat brains were scanned after stereotactic injection of iron in different concentrations into the SN and after injecting ferritin, zinc and 6-OHDA alone, and after the addition of desferrioxamine. The amount of iron in the SN was measured spectroscopically. For iron, and partly for 6-OHDA, in different concentrations, a dose-dependent increase of SN echogenicity could be visualized, corresponding to an increase of iron measured by spectroscopy. No increase of echogenicity was visualized after the injection of ferritin and the addition of desferrioxamine to 6-OHDA, though an increase of iron was measured by spectroscopy. Therefore, we conclude that iron not bound to these proteins may lead to an increase of echogenicity of the SN.

Light-intensity distribution in eccentric photorefraction crescents.

We try to improve the accuracy of eccentric photorefraction by taking more information into account than just the size and tilt of the crescent. Based on Gaussian optics and the assumption of an isotropic scattering retina, a theoretical analysis of the light-intensity distribution in the pupils of astigmatic eyes is presented. The method is applied to different photorefractor setups (point light source, long linear light source, knife-edge aperture, and circular aperture). In the case of a knife-edge aperture the crescent structure can be formulated analytically. In the case of a circular aperture an analytic description is possible only for spherical refractive errors, but astigmatic refractive errors can be determined from crescent parameters with neural networks.

Effect of repeated immobilization on serotonin metabolism in different rat brain areas and on serum corticosterone.

The effect of daily repeated 10 min immobilization on the serotoninergic neurotransmission and serum corticosterone levels was studied. Male Lewis rats were immobilized for a 10 min period daily once or on 5 consecutive days. Serotoninergic neurotransmission was followed using differential in vivo pulse voltammetry with carbon fibre electrodes measuring extracellular 5-hydroxyindoleacetic acid (5-HIAA) levels. Recordings were performed in brain areas involved in the control of behaviour, mood, and stress response such as the frontal cortex, the hippocampal CA-3 and dentate gyrus, the striatum, and the raphe nuclei dorsalis (NRD) and medialis (MRN). The first immobilization resulted in an increase of the extracellular 5-HIAA levels in all areas under study, except the striatum where no reaction was observed. The major effect was recorded in the frontal cortex, showing an increase of about 400% as compared to control, which lasted for 3h after the end of the immobilization period. Beginning on day 2 in all areas, except the striatum, a consecutive habituation to the stressor seemed to occur, since the stress-induced increase in the voltammetric signal was found to be reduced after consecutive immobilization. Serum corticosterone levels were measured directly after a single and after 5 daily immobilization periods. After single immobilization the serum corticosterone level was found to be about 270 ng/ml. After the 5th immobilization about 300 ng/ml were detected. These differences were not found to be significant. In summary, our data indicate that the serotonin metabolism shows habituation in nearly all brain areas after repeated immobilization, though the corticosterone level at the end of the immobilization period was comparable after single and repeated immobilization.

Analysis of GTP-binding proteins, phosphoproteins, and cytosolic calcium in functional heterogeneous human blood platelet subpopulations.

The biochemical basis for the functional heterogeneity of human blood platelets was investigated in terms of protein phosphorylation, cytoplasmic calcium ([Ca2+]i), the ratio of 46 and 50 kDa vasodilator-stimulated protein (VASP), and GTP-binding proteins (G-proteins). Platelets were fractionated by density. Comparing resting low-density platelets (LDP) to high-density platelets (HDP) revealed higher phosphorylation of proteins in the 47, 31, and 24 kDa ranges. A higher phosphorylation of the 20 kDa protein in LDP compared to HDP was related to an enhanced [Ca2+]i, an increased ADP-ribosylation of the inhibitory G-protein (G(i alpha1-3)) and rhoA, and a decreased ADP-ribosylation of the stimulatory G-protein (G(s alpha)). The differences in the ribosylation patterns of the subpopulations were not influenced by thrombin stimulation or exposure to prostaglandin E1 (PGE1). An 18 kDa phosphoprotein was more highly phosphorylated in resting HDP than in LDP. Thrombin exposure caused dephosphorylation of the 18 kDa phosphoprotein in the HDP, but generally increased phosphorylation of both HDP and LDP in the 47, 31, 24, and 20 kDa bands. Preincubation with prostaglandin E1 or sodium nitroprusside diminished the subsequent thrombin-induced increase in phosphorylation, particularly in HDP. In unstimulated HDP, the 50 kDa VASP phospho form was enhanced, whereas in unstimulated LDP the 46 kDa VASP dephospho form was increased. Our findings suggest that the functional heterogeneity of platelets is partly derived from differences in signal transduction mechanisms reflected in varying phosphoprotein patterns and G-protein properties of platelet stimulatory and inhibitory pathways.