Reidulf G. Watten

Oculomotor factors in the aetiology of occupational cervicobrachial diseases (OCD)

SummaryThe traditional posture-ergonomic perspective on the aetiology of Occupational Cervicobrachial Disease (OCD) is discussed and criticized in the light of present knowledge of oculomotor strain during sustained visual work at short distances.Two experiments on ocularly induced neck muscular tension are reported. In both experiments EMGs were taken from six different muscles in the head, neck and shoulder region during a visual discrimination task. In Experiment 1, accommodation and fusion requirements were systematically varied by changing viewing distance in combination with the application of minuslenses and base-out prisms. EMG was shown to increase as a function of accommodation and fusion load. In Experiment 2, a clinical population with severe and long lasting neck and shoulder problems and inappropriate optical corrections was studied with the same experimental design. EMG was shown to decrease when habitual corrections were replaced by more apppropriate ones.

Visual functions and acute ingestion of alcohol

In a placebo‐controlled experiment comprising 22 healthy men (mean age 27.4 years), we investigated the influence of three breath levels of blood alcohol (BrAC; 0.0%, 0.05% and 0.1%) upon distant visual acuity, stereoacuity, contrast sensitivity, accommodation, resting focus of accommodation and binocular vision. Positive (PRA) and negative accommodation (NRA) and resting focus of accommodation showed no significant changes with increasing BrAC. Compared to the placebo condition, visual acuity and refraction were only significantly affected at a breath alcohol level of 0.1%. Contrast sensitivity, stereoacuity and binocular vision were affected both at BrAC 0.05% and BrAC 0.1%. Only the higher spatial frequencies of contrast sensitivity were affected.

Quality of life, intelligence and mood

We investigated the relationship between quality of life (QOL), general ability and current mood in a sample of young men (N=269, mean age 24.9 years). Intelligence (verbal, spatial and mathematical) and technical ability were uncorrelated with QOL. Current mood such as pleasure, anger, sadness, boredom correlated firmly with QOL. The paper concludes that intelligence seems to be a variable of minor interest for QOL-studies.

Reinvention of visual fatigue: accumulation of scientific knowledge or neglect of scientific history?

The development of science is believed lo be a continuous accumulation of knowledge, giving rise to the somewhat false idea that the most recent knowledge is the most valid and most appropriate. Neglect of the history of a scientific discipline might therefore lead to reinvention of theories that have already been proposed and experimentally investigated. In the case of visual fatigue the pioneering works of Lucien Howe. Walter Lancaster and others at the beginning of this century are very similar to contemporary work in terms of conceptual definitions, methodological approach, assessment and results. The temporal and dynamic aspects of accommodation and vergence considered important today were intensely studied and discussed by Howe and others.

PERSONALITY AND QUALITY OF LIFE

The present study investigated a possible association between personality, mental absorption and quality of life (QOL) in a sample of young males (N=411). Mental absorption was assessed with Tellegens Absorption Scale (ABS). Using a 6 dimensional QOL-scale we found the Millon Behavior Health Inventory (MBHI) dimensions Basic coping style, Psychogenic attitudes, Psychosomatic correlates and Prognosic indices, to be firmly related to QOL, explaining 44% of the variance of a QOL scale which was derived through factor analysis. Mental absortion was weakly related to QOL. The discussion revolves around the relationship between personality and perceptual style, health report behavior and personality as possible biasing factor in evaluative QOL-investigations.

Negative affectivity and intellectual ability: A study of their relation to self-reported physical symptoms, perceived daily stress and mood, and disciplinary problems in military recruits

In this study we examined the relationship between cognitive ability and Negative Affectivity (NA) (measured as cognitive and behavioral aspects of anxiety) on the one hand, and somatic complaints, symptom attribution (i.e. subjective evaluation of psychological vs somatic symptom causes), perceived daily stress/mood, and disciplinary problems on the other hand, in a sample of military recruits. As expected, cognitive and behavioral anxiety correlated with measures of somatic complaints and with perceived stress/negative mood in the daily service, as well as with symptom attribution. General ability correlated negatively with three of the five somatic complaint scales as well as with presence of disciplinary problems after controlling for NA. However, the effect of the ability factor on these dependent variables was very weak and difficult to interpret. On the whole, cognitive ability does not seem to be an interesting variable in research on the NA-somatic complaints relationship, at least as conceptualized on the trait level. Thus, cognitive ability appears to be of less importance as an explanatory factor in theories of symptom perception and symptom attribution.

Time course of contrast adaptation to VDU-displayed text

Abstract VDU text-editing induces contrast adaptation at the predominant spatial frequencies (periodicity) of the text page. Visual contrast sensitivity was tested after 10 and 60 min reading of VDU-displayed text of positive and negative contrast polarity. Contrast sensitivity impairments in-the order of 0-4 to 0-7 log unit change in contrast thresholds were observed. This contrast threshold elevation after-effect decays as a power function of time, with time required to recover from adaptation approximately corresponding to the reading times. At low spatial frequencies (horizontal periodicity of rows), displays of negative polarity induce stronger contrast adaptation than displays of positive polarity, at medium spatial frequencies (vertical periodicity of characters) no effect of contrast polarity was observed. The results are discussed in relation to VDU-induced visual fatique.

Are parents of asthmatic children different from other parents? Some follow-up results from the Norwegian PRAD Project.

Follow-up results from the Norwegian PRAD study (Psychosocial Risk for Allergic Development) show that parents of children who later developed symptoms of asthma were different from a control group of parents with normal, nonsymptomatic children several years preceding the disorder. There were significant within-pair differences in self-reported marital adjustment (DAS-Dyadic Adjustment Scale) for the control group but not for the asthma group. There were no significant between-pair DAS scores for the two groups of parents. The two groups of parents also differed in perceiving how the child had influenced their lives, in description of the childbirth and partially in childcare style. The assumed relationship between parental characteristics and asthma in children is being discussed, and the paper concludes that parents of asthmatic children should be regarded as a risk factor and clinical and therapeutic routines should be developed accordingly.

Spatial-frequency discrimination, brain lateralisation, and acute intake of alcohol

The effect of alcohol (breath-alcohol level of 0.1%) on perceptual discrimination of low (1.5 cycles deg−1) and high (8 cycles deg−1) spatial frequencies in the left and right visual field was measured in eighteen right-handed males, in a double-blind, balanced placebo design. Discrimination thresholds for briefly (180 ms) presented sinusoidal gratings were determined by two-alternative forced-choice judgments with four interleaving psychophysical staircases providing random trial-to-trial variation of reference spatial frequency and visual field, in addition to a random (±10%) jitter of reference spatial frequency. Alcohol produced overall higher discrimination thresholds but did not alter the visual-field balance: no main effect of visual field was observed, but in both placebo and alcohol conditions spatial frequency interacted with visual field in the direction predicted by the spatial-frequency hypothesis of hemispheric asymmetry in visual-information processing, with left-visual-field/right-hemisphere superiority in discrimination of low spatial frequencies and right-visual-field/left-hemisphere superiority in discrimination of high spatial frequencies.

VDU work, contrast adaptation, and visual fatigue

Abstract Prolonged VDU work leads to a number of detrimental changes in visual performance and to frequent complaints about asthenopia, musculoskeletal, and other symptoms. The relationship between changes in contrast adaptation at five spatial frequencies and workrelated symptoms were studied in an experimental approach with two groups, one working 2 h (n=13) and the other 4 h (n = 17). Both groups showed a significant reduction in visual acuity and contrast sensitivity, but there were no significant differences between working two or four hours. The relationship between contrast adaptation and symptoms showed a mixed pattern. For the 2 h group there was significant positive correlation between symptoms and all spatial frequencies. For the 4 h group there were mixed correlations between symptoms and contrast adaptation. The results offer only partial support to Lunn and Banks hypotheses on contrast adaptation, accommodation control and visual fatigue symptoms. Contrast adaptation saturates after 1-2 h a...