SIGNIFICANCE Computer-specific progressive addition lenses (PC-PALs) are shown to reduce computer vision syndrome (CVS) symptoms, increase visual comfort and tolerance, and improve body posture at the personal computer. They are highly preferred by computer workers. Increasing their use may aid prevention measures within the workplace health management. PURPOSE This study investigates whether technical differences between general-purpose progressive addition lenses (GP-PALs) and PC-PALs are subjectively manifest in CVS. MATERIALS AND METHODS One hundred ninety presbyopic visual display unit (VDU) workers aged 53 ± 6 years (mean ± SD) were fitted with GP-PALs and PC-PALs in a subject-masked, randomized, crossover study. Subjects tested both corrections at their personal workplace for 2 weeks each, for VDU work only. Comfort and lens type preferences were assessed using a 24-item questionnaire developed for this study. RESULTS Computer vision syndrome was perceived approximately seven times more often with GP-PALs compared with PC-PALs. Eighty-four percent of subjects preferred PC-PALs for their VDU work. Computer-specific progressive addition lenses ratings were statistically and clinically significantly better than GP-PALs (5.95 vs. 4.42 of 7 points; 1.53; 95% confidence interval, 1.20 to 1.85). An existing ametropia or prior experience with PALs did not influence the score. Only 14.2% of subjects had received information about specific VDU eyewear from their optician or optometrist, whereas 79% expressed the wish to be informed about these products. CONCLUSIONS Computer-specific progressive addition lenses reduce the perception of the CVS and are highly preferred by VDU workers.
SIGNIFICANCEDuring computer work in controlled laboratory conditions, wearing multifocal contact lenses (MFCLs) showed no lower muscle load but increased subjective perception of comfort with equivalent visual quality and comparable tolerance.PURPOSEBecause musculoskeletal complaints are frequent among computer workers, this study used the muscle electrophysiological activity of shoulder and neck muscles in presbyopic computer workers who received either progressive addition lenses for general purpose (GP-PALs) or MFCLs.METHODSFor this crossover study, 11 presbyopic computer workers aged 55 ± 4 years (mean ± standard deviation) were equipped with GP-PALs and MFCLs in a randomized order. Surface electromyography signals were recorded bilaterally from shoulder and neck muscles during short-term computer work tasks using an optimally adjusted visual display unit workplace. The amplitude probability distribution function, the number and total duration of EMG gaps, and sustained low-level muscle activity periods of the surface electromyography signals were calculated. Comfort and correction type preferences were assessed. Head inclination was objectively evaluated.RESULTSMultifocal contact lenses elicited no significant lower muscle load than GP-PALs. The number of sustained low-level muscle activity periods longer than 60 seconds was similar between visual aids. The total amount of gaps was significantly higher with MFCLs (44 gaps) compared with progressive addition lenses for general purpose (15 gaps) in all analyzed periods for all participants. However, there were no significant differences for the median in the intraindividual comparisons (P = .22, dz = 0.52). Multifocal contact lenses scored statistically significant higher in comfort values with equivalent visual quality and comparable tolerance (P = .003, dz = 1.51).CONCLUSIONSAlthough the study failed to show clear results, wearing MFCLs seems to enhance working comfort compared with GP-PALs subjectively.
IntroductionIn this interventional study, the ergonomic workplace set‐up and the impact of character size on subjectively estimated working productivity and computer vision syndrome (CVS) were evaluated in the field.MethodsThe number of displays and their size, resolution, surface structure, position in the room and relation to the eye were evaluated for 152 units. CVS was assessed using the CVS‐Questionnaire. Habitually used character size for an uppercase E was recorded and compared to the ISO 9241–303:2011, national standards (e.g., ANSI/HFES 100–2007) and national guidelines (e.g., German DGUV Information 215–410). In case of failure to comply with these standards, character size was increased to 22 angular minutes to reach the recommended ranges. Reasons for returning to former or smaller character sizes were recorded, and subjectively perceived changes in productivity were estimated by the participants using a visual analogue scale before and 2 weeks after the intervention using a questionnaire.ResultsThe average visual display unit consisted of two non‐glare (matt) 24″ widescreen monitors that were located approximately 73 cm (primary) and 76 cm (secondary) from the eyes. The mean (SD) habitually set character size was 14.29 angular minutes (3.53) and therefore both statistically and clinically significantly too small compared with ISO 9241–303:2011 (p < 0.001). Increasing the character size to 22 angular minutes produced a 26% reduction in subjectively rated productivity (p < 0.001). No significant correlation between character size and symptoms of CVS was demonstrated.ConclusionsIn the workplaces investigated, recommendations for character size were not adhered to. This resulted in a reduction in productivity and was not compatible with some of the work requirements, for example, obtaining a broad overview of a spreadsheet.
IntroductionThis study analysed the impact of general purpose progressive addition lenses (GP‐PALs) and computer progressive addition lenses (PC‐PALs) on the activity of the trapezius muscle during computer operation.MethodsIn this randomised, single‐blinded, crossover study, surface electromyography (SEMG) signals were recorded bilaterally from the trapezius muscle during a 30‐min computer task performed wearing different presbyopic corrections. The amplitude probability distribution function and its percentiles, gap frequency, muscular rest time and sustained low‐level muscle activity periods were analysed in 32 subjects with artificially induced presbyopia. Subjectively perceived differences in vision and postural load between lenses were evaluated using a seven‐item questionnaire (non‐standardised, visual analogue scale ranged from 1 [bad] to 100 [good]).ResultsConsidering the SEMG data, no significant difference in the muscular activity of the trapezius muscle was observed when using GP‐PALs or PC‐PALs for computer operation. However, PC‐PALs showed statistically and clinically significantly higher results for subjectively perceived visual quality (78.4–31.3; p < 0.001), spontaneous tolerance (79.2–31.3; p < 0.001) and field of view (75.9–23.5; p < 0.001) compared with GP‐PALs.ConclusionsEven though the electromyographic approach did not show a significant differentiation between the lenses, the subjective evaluation was clearly in favour of PC‐PALs. Eye care practitioners should always take an occupational history of presbyopes, ask about the workplace situation and consider the use of PC‐PALs.
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