ABSTRACT
BACKGROUND: Extensive literature in ergonomics and optometry has indicated that computer use is closely associated with visual problems. Computer-Aided Design (CAD) requires a substantial effort on behalf of the visual system. The manifestations of visual fatigue phenomena may affect the working behavior and the human-system interaction. OBJECTIVE: The aim of this survey is to identify the normal working conditions and how the eventual visual fatigue phenomena are able to influence the working behavior of CAD users. METHODS: A questionnaire was created and submitted to a sample of 150 university students, who attend the Faculty of Engineering of the University of Pisa (Italy). RESULTS: The questionnaire results show that university students spend on average 7 hours per day at the computer for CAD drafting. Most of the participants work in strongly lit environments, with high brightness screens and negative polarity. Such conditions cause high contrasts in luminance, especially between screen and surfaces that fall within the field of vision. The results show that 135 out of 150 students report visual fatigue during long CAD sessions, which in most cases leads to difficulty in continuing the activity and changing usual working behavior. CONCLUSIONS: The results of the questionnaire show that the university students work in highly variable lighting conditions and with little attention on the luminance distribution on the field of view. This has highlighted the importance, for VDT workstations, of not limiting the risk analysis to the postural ergonomics (how usually occurs) but extend it to the workplace as a whole, analyzing also the ergonomics of vision, which involves different consideration on the natural and artificial lighting of the workplace and on the characteristics of the display.
ABSTRACT
BACKGROUND: The association between chronic idiopathic urticaria (CIU) and autoimmune thyroiditis (AT) is known, as well as major prevalence of antithyroid antibodies in the allergical subjects and other autoimmune diseases. We have evaluated the effects of l-thyroxine on clinical symptoms of CIU in AT patients suggesting the hypothesis of a new thyroid-stimulating hormone (TSH) role in immune system. METHODS: In 20 female patients with CIU + AT, both hypothyroid and euthyroid, we have investigated the therapeutic effects of l-thyroxine dosed to suppress the TSH. Free-T3, Free-T4, TSH, antithyroperoxidase and antithyroglobulin antibodies, total immunoglobulin (Ig)E, Rheuma test and eritro-sedimentation rate were monitored during treatment. RESULTS: In 16 patients a strong decrease of urticaria symptoms has happened after 12 weeks. The TPO Ab and HTG Ab clearly decreased in 14 patients. Furthermore, in two patients with rheumatoid arthritis and in two patients with pollen allergy a strong decrease of rheuma test titer and total IgE has happened. CONCLUSION: The reason of AT is associated to CIU and others allergical and autoimmune diseases is poorly known. The exclusive hormonal therapy reduces the symptoms of CIU and inflammatory response in many chronic diseases associated to AT. We suggest a stimulatory effect of TSH able to produce considerable changes of the immune response and immune tolerance in patients with AT causing target organs damage. The causal mechanism involves immune, nervous and endocrine system, sharing a common set of hormones, cytokines and receptors, in a unique totally integrated loop (the neuro-immuno-endocrine axis).
