RESUMEN
PURPOSE: This office field study investigated the effects of different types of spectacle lenses habitually worn by computer users with presbyopia and in the beginning stages of presbyopia. Computer vision syndrome was assessed through reported complaints and ergonomic conditions. METHODS: A questionnaire regarding the type of habitually worn near-vision lenses at the workplace, visual conditions and the levels of different types of complaints was administered to 175 participants aged 35 years and older (mean ± SD: 52.0 ± 6.7 years). Statistical factor analysis identified five specific aspects of the complaints. Workplace conditions were analysed based on photographs taken in typical working conditions. RESULTS: In the subgroup of 25 users between the ages of 36 and 57 years (mean 44 ± 5 years), who wore distance-vision lenses and performed more demanding occupational tasks, the reported extents of 'ocular strain', 'musculoskeletal strain' and 'headache' increased with the daily duration of computer work and explained up to 44 per cent of the variance (rs = 0.66). In the other subgroups, this effect was smaller, while in the complete sample (n = 175), this correlation was approximately rs = 0.2. The subgroup of 85 general-purpose progressive lens users (mean age 54 years) adopted head inclinations that were approximately seven degrees more elevated than those of the subgroups with single vision lenses. CONCLUSIONS: The present questionnaire was able to assess the complaints of computer users depending on the type of spectacle lenses worn. A missing near-vision addition among participants in the early stages of presbyopia was identified as a risk factor for complaints among those with longer daily durations of demanding computer work.
Asunto(s)
Computadores , Anteojos , Presbiopía/terapia , Agudeza Visual/fisiología , Adulto , Progresión de la Enfermedad , Diseño de Equipo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Presbiopía/etiología , Presbiopía/fisiopatología , Encuestas y Cuestionarios , SíndromeRESUMEN
BACKGROUND: Two types of progressive addition lenses (PALs) were compared in an office field study: 1. General purpose PALs with continuous clear vision between infinity and near reading distances and 2. Computer vision PALs with a wider zone of clear vision at the monitor and in near vision but no clear distance vision. METHODS: Twenty-three presbyopic participants wore each type of lens for two weeks in a double-masked four-week quasi-experimental procedure that included an adaptation phase (Weeks 1 and 2) and a test phase (Weeks 3 and 4). Questionnaires on visual and musculoskeletal conditions as well as preferences regarding the type of lenses were administered. After eight more weeks of free use of the spectacles, the preferences were assessed again. The ergonomic conditions were analysed from photographs. RESULTS: Head inclination when looking at the monitor was significantly lower by 2.3 degrees with the computer vision PALs than with the general purpose PALs. Vision at the monitor was judged significantly better with computer PALs, while distance vision was judged better with general purpose PALs; however, the reported advantage of computer vision PALs differed in extent between participants. Accordingly, 61 per cent of the participants preferred the computer vision PALs, when asked without information about lens design. After full information about lens characteristics and additional eight weeks of free spectacle use, 44 per cent preferred the computer vision PALs. CONCLUSION: On average, computer vision PALs were rated significantly better with respect to vision at the monitor during the experimental part of the study. In the final forced-choice ratings, approximately half of the participants preferred either the computer vision PAL or the general purpose PAL. Individual factors seem to play a role in this preference and in the rated advantage of computer vision PALs.
Asunto(s)
Computadores , Anteojos , Miopía/terapia , Presbiopía/terapia , Agudeza Visual , Adulto , Diseño de Equipo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Miopía/fisiopatología , Presbiopía/fisiopatología , Encuestas y CuestionariosRESUMEN
BACKGROUND: This study intended to measure the near and far points of clear vision as a function of the inclination of the line of sight with comfortable head posture. Measurements with different lenses for presbyopic correction were made to suggest comfortable positions of the monitor for computer work. METHOD: An 'inclined optometer' was built, including a concave mirror to shift a visual target of constant angular size from near to infinity (proposed by Reiner). The optometer could be inclined vertically from horizontal to 50 degrees downward to vary the inclination of the line of sight. Measurements were made with a comfortable head position adjusted on a headrest. RESULTS: The near and far points were plotted both in the unit one/metre as a function of eye inclination (optometric diagram) and also as positions from the eyes in workspace co-ordinates (workplace diagram). First, individual examples of plots of the vertical zones of clear vision at the workplace are shown. Second, the group mean data of 22 observers with newly prescribed lenses showed that the vertical zones of clear vision for general purpose progressive addition lenses (PALs) reach infinity and are flatter, while computer vision PALs lead to more steep vertical zones ending at intermediate distances. Third, the mean results of three samples from our laboratory were compared with respect to general purpose PALs, which are most frequently used by presbyopic people. CONCLUSIONS: The diagrams of the vertical zones of clear vision for different spectacles provide information on the ergonomic vertical position of computer monitors for clear vision with a comfortable head position. The grand mean of general purpose PALs suggests that the upper edge of the monitor should be at least approximately 15 cm below eye level at a typical viewing distance of approximately 75 cm. Higher monitor positions are possible with computer vision PALs.
Asunto(s)
Terminales de Computador , Movimientos Oculares/fisiología , Anteojos , Presbiopía/terapia , Agudeza Visual , Diseño de Equipo , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Presbiopía/fisiopatologíaRESUMEN
The aim of this study was a proof of concept to examine the effects of a Web-based office ergonomics intervention on subjects' individual workplace adjustments. An intervention study was conducted with 24 office workers lasting 6 weeks with three consecutive phases (before, 1 and 5 weeks after the intervention). Employees used a purpose-made website for adjusting their computer workplaces without any personal support of ergonomics experts. Workplace measurements were taken directly on site and by analysing photos taken of the employee. Self-reported complaints were assessed by filling in a questionnaire. It was found that 96% of the employees changed their workplaces on their own and retained them mostly unchanged after the intervention. Furthermore, self-reported musculoskeletal complaints and headache symptoms decreased significantly after the intervention. These findings suggest an improvement of workplace conditions so that cost-effective ergonomic Web-based interventions appear promising in further research and application.
Asunto(s)
Astenopía/prevención & control , Ergonomía/métodos , Cefalea/prevención & control , Internet , Dolor Musculoesquelético/prevención & control , Enfermedades Profesionales/prevención & control , Adulto , Terminales de Computador , Femenino , Humanos , Masculino , Persona de Mediana Edad , Salud Laboral , Lugar de Trabajo , Adulto JovenRESUMEN
With dichoptic nonius lines presented repetitively on a computer monitor for only short moments in time (e.g., 80 ms), temporal aspects of vergence can be assessed: the variability of fixation disparity with a stationary central fusion stimulus and the velocity of convergence or divergence changes. Results and test-retest correlations of these psychophysical vergence measures are shown for children and adults. In most children older than about 7 years, the estimation of vergence velocity turned out as well as in adults in terms of amount and reliability.