TY  - THES
A1  - Bogert, Annika
T1  - Silicone Hydrogel Orthokeratology for the Correction of Low Myopia
N2  - Aim Patrick J. Caroline and Mark P. Andre first reported about soft lens orthokeratology in 2005. In a number of articles in the past five years, they reported about their research on this topic and their new findings. The aim of this study was to continue the research of Patrick J. Caroline and Mark P. Andre and to collect more information about the outcome of the technique. Methods Ten subjects with low myopia from -0.25 D to -1.25 D and a refractive astigmatism from plano to -0.75 D were fitted with a -10.00 D CIBA VISION AIR OPTIX® NIGHT&DAY® silicone hydrogel contact lens and were told to wear the lenses over night and everted. Corneal topography and refraction measurements were taken after one night, one week and one month of contact lens wear. Results Eight out of ten subjects finished the study, six female and two male. The mean age of the subjects was 23.9 years. With the eight subjects who finished the study, the mean change in subjective refraction was about +1.00 D in the sphere and +0.22 D in the cylinder, with maximum changes of +1.75 D sphere and +0.75 D cylinder. The mean apical power change, measured with the topographer, was 1.11 D. Changes in K - readings ranged from slight corneal steepening in both of the meridians to 0.23 mm of corneal flattening in the horizontal meridian and 0.27 mm of corneal flattening in the vertical meridian. Corneal eccentricity decreased about 0.65 on average. The main complaints and problems were the high minus power and the decentration of the contact lens and the occurrence of ghosting at night. Conclusion The results of this study show that everted wear of a high minus silicone hydrogel contact lens can lead to orthokeratology - such as changes in corneal topography and subjective refraction. These changes range from plano to +1.75 D sphere and +0.25 D to +0.75 D cylinder but are unpredictable and vary from subject to subject. Additional studies regarding the contact lens decentration and the unpredictability of the outcome need to be done to optimize the process.
KW  - Orthokeratologie
KW  - Orthokeratology
KW  - Myopia
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus-29
ER  - 
TY  - THES
A1  - Vogel, Ellen
T1  - Analysis of the Structural Formal Elements of Adjustment Process offered by German Companies in Baden-Württemberg
N2  - This paper aims to provide essential information about the formal aspects of the adjustment process companies in Southern Germany utilize to adjust their employees to new surroundings. In particular, it shall be investigated and defined what formal aspects are and when firms apply them. Literature shows that companies do implement language courses, intercultural trainings or provide further information about the host country before a stay abroad. Nevertheless, the phases during and after the assignment are not taken into account with the required importance. Additionally, since national culture can be broken down into different layers, the organizational culture as one layer was analyzed, too.By conducting a quantitative research among companies in Baden-Württemberg, this paper shows the different approaches for dealing with a stay abroad. Scientific literature about the topic of adjustment of globally assigned workers shall help emphasizing the need of a deeper cultural insight. Furthermore, by attempting to explain the organizations’ culture, a better understanding of the chosen training methods shall be created. Definitions in the beginning helped to understand the concept of culture, the notion and the phases of adjustment. Almost all collected data has been accessed either through JSTOR (a digital library founded to help academic libraries or publishers) or similar databases, through the companies’ websites or through the survey results it selves.The results of this research show that the phase before the stay abroad is organized well. Companies offer pre-departure training, but during and after the expatriate time a lack of support is being observed. The firms obviously underestimate the necessary help needed during the assignment and in the return phase, which is why the thesis attempts to fill this gap. Through the organizational culture, described on the companies’ webpages the author was able to draw a conclusion to the applied training methods, which results in a consistent overall picture of the described firms. Companies from the automotive sector had the highest return rate in the survey, which is why particular attention was paid to it.
KW  - National/Organizational Culture
KW  - Cross-Cultural Training
KW  - Adjustment Process
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus--861
ER  - 
TY  - THES
A1  - Hettich, Philip
T1  - Factors of Success for Share Repurchases: What factors have to be given to ensure that share repurchases create long-term shareholder value? A critical View
N2  - This paper deals with the question of which factors have to be given for
successful share repurchases that create long-term shareholder value. Center of
the thesis is the agency theory and its influence on share repurchases. Based on
theoretical findings success factors for share repurchases are derived and then
verified by case studies.
The main drivers for a successful share repurchase elaborated by this paper are a
suitable long-term executive compensation, an independent board of directors and
a shareholder structure without a majority shareholder. Additionally the findings
show that tying repurchases to certain share price thresholds improves the quality
of share repurchases.
KW  - Share Repurchase
KW  - Undervaluation
KW  - Agency Theory
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus--878
ER  - 
TY  - THES
A1  - Winter, Jessica
T1  - Evaluation of Alternative Powertrains for German Automotive Suppliers
N2  - The present thesis deals with alternative powertrains, focusing on electric vehicles
and hybrid vehicles and which of those alternative powertrains is considered as
sustainable for the future. It explores the question, which alternative powertrain is
worthwhile investing in for German automotive suppliers. The aim is to clarify
which of the two powertrains is already established on the market and what the
future prospects of those powertrains are. The question here is evaluated based on
the analysis of current literature as well as through the use of a SWOT analysis
and the use of the scoring model.
As a result it is clear that there is a need for alternative powertrains and the entire
automotive industry invests a lot in the development and research of alternative
powertrains. According to the German Federal Government, one million electric
vehicles should be on German roads by 2020. With pure electric vehicles, however,
the goal will be difficult to reach. Therefore, there is a lot of vested interest in
the development of hybrid vehicles on the market. It shows that the hybrid vehicle
has considerable advantages over the electric vehicle and the hybrid vehicle is
already seen as a transitional solution for pure electric vehicles. The hybrid vehicle
is also already established in the market and has better chances on the market
in the future. Therefore, it makes sense for German automotive suppliers to invest
in hybrid vehicles and to focus on this market, since there the chances of success
are greater and the future potential of this market is higher.
KW  - Germany
KW  - automotive supplier
KW  - powertrain
KW  - electric vehicle
KW  - hybrid vehicle
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus--986
ER  - 
TY  - THES
A1  - Rothe, Colleen
T1  - Evaluation of Scanpath Comparison Metrics for Static and Dynamic Tasks
N2  - Purpose
Automated scanpath comparison metrics should deliver an objective method to
evaluate the similarity of scanpaths. The aim of this thesis is an evaluation of
seven existing scanpath comparison metrics in static and dynamic tasks in order
to provide a guidline that helps to decide which algorithm has to be chosen for a
special kind of task.
Methods
The applicability of the algorithms for a static, visual search task and a dynamic,
interactive video game task as well as their constraints and limitations were tested.
Therefore, binocular gaze data were recorded by using the eye tracking system The
Eye Tribe (The Eye Tribe ApS, Copenhagen/ Denmark). Objective task performance
measures from 21 subjects were used in order to create scanpath groupings
for which a relevant effect of dissimilarity was to be expected. Objective task performance
measures such as task performance time were statistically evaluated and
compared to the results gained by the comparison metrics.
Results
Four of the algorithms being used successfully identified differences for static and
dynamic tasks: MultiMatch, iComp, SubsMatch and the Hidden Markov Model.
ScanMatch was very sensitive for the static task but not applicable to the dynamic
task whereas FuncSim was suitable for dynamic but not for static tasks. Eyenalysis
failed to detect any effect.
Conclusion
The applicability of scanpath comparison metrics depends on the state of the task,
respectively on the kind of experimental set up. In future, the application area for
eye tracking will expand and an improvement of automated scanpath comparison
metrics is therefore required.
KW  - Eye tracking
KW  - Scanpath
KW  - Comparison metrics
KW  - Visual search
KW  - Fixation
KW  - Mustererkennung
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus4-1633
ER  - 
TY  - THES
A1  - Breher, Katharina
T1  - Visual consequences of Albinism
N2  - Purpose: The purpose of this thesis is to provide a comprehensive literature review about albinism as an inherited metabolic disorder of melanin synthesis along with those related conditions impacting the visual system. As such, it addresses eye care emphasizing the visual consequences of albinism along with diagnostic and treatment options.
Methods: Background knowledge about ocular development is given as well as information about etiological biochemical and genetic processes. The current classification, clinical findings and their assessment and management options are presented based on recent results of research. In conclusion, two case reports are described as examples of visual care options.
Results: Melanin plays a big role in the retinal and chiasmal development. Melanin biosynthesis can be disrupted by different genes in various ways which leads to the current classification of albinism. Clinical findings include fundus hypopigmenta-tion, nystagmus, iris transillumination, photophobia, foveal hypoplasia, excessive chiasmal decussation, reduced visual acuity, high astigmatism (with-the-rule), strabismus and decreased stereopsis. Treatment options to improve visual acuity, fixation and binocularity are (tinted) prescription lenses and contact lenses, low vision aids, surgical procedures and vision therapy. Medication and supplementa-tion for increased pigmentation are currently being tested on mice.
Conclusions: Albinism is caused by genetic mutations resulting in ocular and cutaneous hypopigmentation. It establishes various phenotypes that require different therapy approaches in order to improve vision and therefore quality of life.
KW  - albinism
KW  - low vision
KW  - genes
KW  - melanin
KW  - vision therapy
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus4-1939
ER  - 
TY  - THES
A1  - Frisch, Jasmina
T1  - Determination of stereoacuity thresholds and their inherent test retest reliabilities at various eccentricities with a monitor-based two-rod-test
N2  - Ziel
Ziel der Studie ist es, mit einem zwei Stäbchen Test am Monitor, die Schwellenwertbestimmung an verschiedenen Exzentrizitäten des binokularen Gesichtsfeldes und deren Wiederholbarkeit durchzuführen. Weiter soll die Dauer der einzelnen Messungen festgehalten und ausgewertet werden.
Methode
Die Explorative Studie wurde mit fünf Probanden im Alter von 21 bis 23 Jahren (2 männlich und 3 weiblich) durchgeführt. Zwei schwarze Balken auf weißem Hintergrund, welche unter einem Winkel von 1° bei einer Beobachtungsentfernung von 5.0 Metern erscheinen, bildeten das Stereobild. Der rechte Balken diente als ortsfester Vergleichsbalken, während der linke Balken zu beurteilen war und durch die stereoskopische Parallaxe, entweder nach vorne oder hinten versetzt erschien. Die Schwellenwertbestimmung erfolgte in sieben Exzentrizitäten zu beiden Seiten des Gesichtsfeldes (0° zentral, 5° rechts/links, 10° rechts/links und 15° rechts/links). Die Darbietung und Abfolge der Bilder mit proximalen und distalen Verschiebungen in den verschiedenen Exzentrizitäten erfolgte randomisiert. Die Bestimmung der Grenzwinkel wurde für 4 Probanden in zwei Sitzungen und für 1 Proband in fünf Sitzungen durchgeführt, wovon bei jeder die Zeit festgehalten wurde. Alle Sitzungen waren mindestens 24 Stunden und längstens 7 Tage voneinander getrennt. Die Auswertung erfolgte durch das bilden von Median und den statistischen Tests von Wilcoxon und Kruskal Wallis mit einem 95% Konfidenzintervall (CI).
Ergebnisse
Peripheres Stereosehen verläuft ähnlich abfallend zur Sehschärfe. Während zentral kleinste proximale Winkel von median 5.0 Winkelsekunden (‘‘) und einem CI (0.5‘‘,30.5‘‘) gefunden wurden, stiegen diese auf 112.2‘‘ in 15° Exzentrizität nach links bei proximaler Darbietung. Distal waren es 19.9‘‘ zentral und 112.2‘‘ in 15° nach rechts. Die Wiederholbarkeit der Grenzwinkelbestimmung war zentral und proximal am genauesten, während in 15° nach links und distal die schlechteste Wiederholbarkeit entdeckt wurde. Zwischen den einzelnen Messungen wurden signifikante Unterschiede der Messdauer gefunden. Die Messdauer liegt bei 5.3 (3.2, 8.3) Minuten.
Schlussfolgerung
Stereogrenzwinkel weichen bei Wiederholungen nicht stark voneinander ab. Mit zunehmender Exzentrizität nehmen die Grenzwinkel zu. Durch die Dauer der Messungen, erscheint der zwei Stäbchen Test am Monitor als schnelle Messmethode die für zukünftige Studien hergenommen werden kann. Jedoch ist der Algorithmus, wie auch die Stereoskopischen Bilder fehlerhaft und sollte überarbeitet werden.
N2  - Purpose
To determine the stereo threshold and inherent variability with a monitor-based two-rod test at various eccentricities of the visual field. Additionally, to evaluate the duration of this procedure.
Subjects and methods
A pilot trial was conducted in five ophthalmologically normal subjects (2 male and 3 female) aged 21 – 23 years. Two black rods on white background, which appeared under an angle of 1° were presented in a viewing distance of 5.0 meters. The right rod was stationary, whilst the left rod appeared under a stereoscopic parallax, with an either proximal or distal displacement to the image plane. Threshold determination was assessed at seven eccentricities of the visual field by a staircase method. Eccentricities were 0° centrally, 5° to the right and left, 10° to the right and left and 15° to the right and left of the visual field. Proximal and distal displacement as well as the sequence of eccentricities were presented in random order. Stereo acuity was measured in two different sessions for four subjects and in five different sessions for one subject. For all sessions the duration was recorded. All sessions were separated by a time interval of at least 24 hours and no longer than 7 days. Evaluation was made by Wilcoxon test and Kruskal Wallis test at the 95% confidence level (CI) and the median was assessed for all thresholds.
Results
Stereo acuity declines with increasing eccentricities of the retina similar to visual acuity. While at 0° eccentricity thresholds were found to be lowest with (median) 5.0 seconds of arc (‘’) and the CI (0.5’’, 30.5’’) for all measurements, they increased to 112.2’’ at 15° eccentricity to the left in proximal displacement. Distal it was 19.9’’ centrally and 112.2’’ to the right at 15° eccentricity with CI (0.5’’, 30.5’’) for all measurements.
Repeatability of the threshold determination was found to be best at 0° eccentricity with proximal displacement showing the exact same result in the repetitive session and poorest repetition was found at 15° eccentricity to the left with distal displacement. Distal repeatability was worse than proximal. Median and CI of duration time was 5.3 (3.2, 8.3) minutes.
Conclusion
Stereo acuity thresholds are repeatable however increase with increasing eccentricity. Repetitions of the threshold determination do not vary considerably. The duration of these measurements indicates the monitor-based two-rod test as a fast procedure, that can be applied in future studies. The test program is limited by an imperfect algorithm and the stereoscopic images evoke cues, this should be reworked.
KW  - two-rod test
KW  - stereotest
KW  - stereopsis
KW  - stereoacuity threshold
KW  - repeatability
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus4-1942
ER  - 
TY  - THES
A1  - Krasňanský, Michal
T1  - The evaluation of a new iPad Aniseikonia Test
N2  - Purpose
The purpose of this study was to evaluate the validity of the iPad Aniseikonia Test for
measurement size lens-induced aniseikonia. The iPad Aniseikonia Test is a new
computer-based test designed for measuring aniseikonia in vertical direction. The iPad
Test uses red-green anaglyphs.
Methods
Aniseikonia was induced in 21 subjects by means of afocal size lenses. Resulting
aniseikonia was measured in vertical direction by the iPad Aniseikonia Test. The
measurement was performed in dark condition with appropriate correction of refractive
error. All subject were patients with normal vision with no anisometropia or other
ocular problem.
Results:
Afocal size lenses of known magnification were used to induce aniseikonia. 5
measurements were taken in each subject, ranging from zero to 7 % magnification.
When using the regression analysis, the slope of the fitted line significantly differs from
1. The average slope of regression line is 0,58.
Conclusions:
Only moderate accuracy was found for tested target size and orientation. In all cases the
iPad Aniseikonia Test underestimates the level of aniseikonia. However for gross
assessment of anisometropia in clinical practice it could be successfully used. Further
study with different target size should be addressed.
Y1  - 
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus4-1469
ER  - 
TY  - THES
A1  - Vujko Muždalo, Nataša
T1  - Measurement of Dynamic Visual Acuity with Augmenting Landolt Rings
N2  - Purpose
The purpose of this study was to investigate the correlation of measured visual acuity
(VA) both static and dynamic obtained with static and dynamic measuring tests, as well
as, response time to visual stimulus and analysis of its influence on dynamic visual
acuity. The aim was to compare the results gathered for the three age groups and
analyze the possible differences.
Methods
The test groups consisted of 75 subjects between 10 and 60 years old, categorized in
three age groups. The measurements of static and dynamic visual acuity and reaction
time were conducted. The set of nine tests (five with radial magnification speed and four
simulating driving condition at 72 km/h and 130 km/h) was designed in order to measure
dynamic visual acuity and the set of two tests for reaction time measurement.
Results
Compared to static visual acuity in both tests, the results obtained with measurements
of dynamic visual acuity resulted in lower values depending on Landolt ring size and
magnification speed of animation. In average, the dynamic visual acuities in tests with
different magnification speeds were lower than static by 0.4 visual acuity units, or 31%
and the average of dynamic visual acuity after subtracting motoric component (reaction
time) was for 0.2 visual acuity worse than static or 15%. In the second test simulating
driving conditions at 72 km/h the average drop in dynamic visual acuity was 33% while
at 130 km/h average drop for younger and middle age groups was 37% and for older
group was 44% and after subtracting motor component values for 72 km/h speed
simulation average drop in visual acuity values was 23% for all three groups; for 130
km/h speed simulation younger and middle aged group average drop of visual acuity
was 20% and with older group it was 24%.
Conclusion
The tests used in this study were simple and fast and revealed significant difference
between static and dynamic visual acuity and influence of reaction time on dynamic
Nataša Vujko Muždalo Abstract
2
visual acuity values. It is hoped that this thesis will be a positive contribution in testing
and training of dynamic visual and sensory response skill with drivers, sportsmen and
people with visual-motor dysfunction.
Keywords: Dynamic visual acuity (DVA), static visual acuity (SVA), reaction time (RT),
motoric component, dynamic visual acuity test, reaction time test, radial increase in size
Y1  - 
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus4-1474
ER  - 
TY  - THES
A1  - Majdak, Vjekoslav
T1  - Influence of Physiological Factors on Stereopsis
N2  - A good stereopsis (depth perception) is needed in everyday life, regardless whether a person is a professional driver or chef. Good estimation of distance, and of what is further and what closer, could mean the difference between a crushed and a whole car or between a bloody and a healthy finger. The main theme of this Master thesis is detect and quantify major factors in depth perception. Do the younger estimate the depth better than the older; do they have better depth perception with greater or smaller pupil distance; does depth perception depend on gender; what happens with stereopsis when vision is fogged by +0,5 and +1,0 D? These are the questions dealt with in this Master thesis.
To answer these questions measurements were made on 51 subjects (mean age 45,0 +/- 13,32 years) of whom 25 were women, mean age 45,5 +/-13,55 years (12 with PD<62 mm, mean and 13 with PD>66 mm) and 26 men, mean age 44,4 +/- 13,34 years (13 with PD<62 mm and, 13 with PD >66 mm). Each of these four groups was further divided by age (one in range 20 to 35 years and second in range 50 to 65 years).
The measurements were made with a few assumptions. The first assumption was that stereopsis is in direct correlation with visual acuity, the second assumption was that persons with bigger interpupillar distance have better stereopsis, and the third assumption was that with age the stereopsis ability decreases.
The measurements were done with modified Frisby–Davis test expanded from four geometrical shapes to twenty-five circles. The stereopsis was measured with full refractive correction at 4,5 and 3,0 meters. Later, stereopsis was measured with fogging with +0,5 and +1,0 D at the 4,5 and 3,0 meter distances.
Statistically there is no correlation (or very weak) between stereopsis and the visual acuity for whole group of 51 test persons, but if only young test persons are taken in consideration, the correlation becomes significant, r(20)=0,566, p=0,009 at 4,5 m and r(20)=0,456, p=0,043 at 3,0 m and that matches the assumption. Stereopsis is in no or weak positive correlation with pupil distance r(51)=0,059, p=0,679, which is in total contrast to the assumption. Stereopsis is in positive correlation with age at 4,5 meters measuring distance, r(51)=0,371, p=0,007, which corresponds to assumption. In addition, stereopsis is better in females than in males by 32,5%.
Based on the results it can be concluded that the stereopsis is in negative correlation with age, in positive correlation with visual acuity, females have better stereopsis than males and statistically, the correlation between stereopsis and pupil distance (PD) has not been proved. The most important conclusion is that the decreased visual acuity brings significant fall of stereopsis. A deficit in refraction of -0,50 D decreases stereo acuity by about 90% (nearly 2x) and a deficit of -1,0 D decreases stereo acuity by about 220% (about 3x).
Keywords: Stereopsis, stereo acuity, depth perception, pupil distance (PD), visual acuity (VA).
Y1  - 
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:944-opus4-1488
ER  -