Felix Walz

Saccadic eye movements after low-dose oral alcohol exposure

OBJECTIVES The influence of low-dose alcohol intake on reflexive visually guided saccades was investigated. METHODS 40 healthy human subjects were orally given alcohol resulting in low-dose alcohol concentration (less than 0.8‰) blood alcohol concentration. Before and after exposure, horizontal saccadic eye movements were recorded at several points in time. The recordings were evaluated with regard to accuracy of the eye movements, latency, the peak eye velocity and the time constant that characterizes the main sequence. The results were compared to recordings from a reference group. RESULTS It was found that the saccadic eye movement was clearly altered by low-dose alcohol intake. However, its characteristics were not unambiguously pathological when compared to the reference group, even though the subjects reported a moderate to strong effect of alcohol and there were clear signs of inebriation. CONCLUSIONS The findings render the evaluation of saccades unsuitable as a simple test for the detection of low-dose alcohol intake.

Saccadic eye movement performance as an indicator of driving ability in elderly drivers

OBJECTIVE Regular checking of the fitness to drive of elderly car-license holders is required in some countries, and this will become increasingly important as more countries face aging populations. The present study investigated whether the analysis of saccadic eye movements could be used as a screening method for the assessment of driving ability. METHODS Three different paradigms (prosaccades, antisaccades, and visuovisual interactive (VVI) saccades) were used to test saccadic eye movements in 144 participants split into four groups: elderly drivers who came to the attention of road authorities for suspected lack of fitness to drive, a group of elderly drivers who served as a comparison group, a group of neurology patients with established brain lesion diagnoses, and a young comparison group. The group of elderly drivers with suspected deficits in driving skills also underwent a medical examination and a practical on-road driving test. The results of the saccadic eye tests of the different groups were compared. RESULTS Antisaccade results indicated a strong link to driving behaviour: elderly drivers who were not fit to drive exhibited a poor performance on the antisaccade task and the performance in the VVI task was also clearly poorer in this group. CONCLUSIONS Testing saccadic eye movements appears to be a promising and efficient method for screening large numbers of people such as elderly drivers. This study indicated a link between antisaccade performance and the ability to drive. Hence, measuring saccadic eye movements should be considered as a tool for screening the fitness to drive.

Pressure aberrations inside the spinal canal during rear-end impact

Minor soft tissue injuries of the cervical spine increasingly pose problems in public health. Such injuries are conveyed particularly often in rear-end automobile collisions at low impact speeds and it has been established that they may be associated with long-term impairment. As a possible cause for this type of injury it has been hypothesized that pressure pulses induced in cervical fluid compartments during the impact could damage the membrane of spinal nerve cells. To date, animal as well as cadaver experiments performed support this hypothesis. A theoretical analysis has been undertaken in order to investigate the pressure and flow pulse emerging in a cervical fluid compartment under conditions representing rear-end impacts with a Dv of 15 km/h. Using the finite element (FE) method, a three-dimensional model of the cervical spine was developed. The model consists of eight vertebrae (C1-T1), the intervertebral discs, the intervertebral joints, all the major ligaments, most of the neck muscles and the head. Additionally, a typical venous blood vessel was included. To determine the pressure behaviour inside the blood vessel, fluid-structure interaction was taken into account. For the time interval including the development of the S-shape, the pressure pulses were calculated and found to be in qualitative agreement with the reported measurements. The shear stresses acting on the vessel wall can be determined from the associated flow pulses. An extrapolation of the results into the interstitial space where nerve cells are located at this stage does not allow assessment of whether a damage threshold may be reached.

Reply to: Technical Comment on "Saccadic eye movement performance as an indicator of driving ability in elderly drivers".

With regard to the letter by Vaucher et al., it should be stressed that neither the premise of our study nor our conclusions are reflected correctly in this comment. As described in our paper, it is not intended to use solely a saccadic eye test to make a final decision on the ability to drive. However, our study indicates that such a test can be helpful as a screening tool, i.e. as a first step determinant to pre-select individuals who are likely to perform poorly as a driver and thus need a more detailed assessment. Given the high number of examinations that can be expected owing to our aging population, we believe that efficient and reliable test procedures are necessary to assess the ability to drive.

Injuries of the Pelvis and the Lower Extremities

Injury to the lower extremities play a major role in sports (soccer, skiing, etc.). They have furthermore emerged as the most frequent non-minor injury resulting from frontal vehicle crashes since restraint systems (belts, airbag in frontal impacts) are not particularly designed for the protection of the legs (and arms). Yet, injuries of the extremities are often the reason for long-term impairment [Haland et al. 1998, Crandall 2001].

Solutions to exercises

Most chapters include questions which allow the reader to test and deepen his/her understanding. Exercises start with the letter E. In the following solutions to these exercises are presented. In addition problems (labelled with P) are provided. Solutions of those problems are available for lecturers only and can be obtained directly from the publishers.