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M. Bregu, L. Tonini, R. Nuzzi, F. M. Grignolo; Evaluation of Asthenopia in VDT Users. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1021.
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In this study we evaluated the possible factors determining asthenopia in VDT (video terminal) users namely years, number of years, number of hours of VDT use, refractive status and working environment conditions.
500 VDT users answered a questionary covering their medical and ophthalmological history. All 500 subjects underwent a complete ophthalmological exam and were asked to grade their perception of asthenopia "0=absent, 1= mild, 2=medium, 3=high".We divided subjects in 2 groups depending on their refractive status: "A" with no need of lens prescription or change and "B" who needed lens prescription or change.
Group A presented BCVA (best corrected visual acuity) = 18,4/20 ± 3,2 (SD) in OD and BCVA = 18,6/20 ± 2 (SD) in OS. Group A subjects had: emmetropia (43 % in OD, 36% in OS), myopia (28% OD, 23% OS), astigmatism (24% OD, 33% OS), hypermetropia (5% OD, 8% OS). In 80% of subjects in group A the use of VDT ranged 1-15 years, in 6% <1 year, in 6% = 16-20 years, in 8% = 21-25 years (8%). Daily use of VDT was 1-7 hrs in all subjects of group A with no participant using VDT >1 hr or >7 hrs.Group B presented BCVA= 15,6/20 ± 2,6 (SD) in OD and BCVA = 15/20 ± 3 (SD) in OS with prior to adequate correction. Their BCVA after adequate correction was 19/20 ± 2 (SD) in OD and 19,4/20 ± 1,2 (SD) in OS. Group B subjects had: myopia (13% OD, 24,5% OS), astigmatism (63,5% OD, 44% OS), hypermetropia (23,5% OD, 31,5% OS).In 87% of subjects in group B the use of VDT ranged 1-15 years, in 6% <1 year, and 7% did not answer to this question. Daily use of VDT was 1-7 hrs in 96% and 4% did not answer. Asthenopic symptoms were various with anxiety, insomnia, asthenia being the most common followed by headache, nausea, hyperlacrimation, blurred distant and near vision, dyplopia, red eye.The following conditions were monitored in the working environment: windows, types of light, protections, VDT screen height compared to the eye level, position of working desk. No ocular disease was found in any of the subjects during full ophthalmological exam.
BVCA in group A was significantly better (p= 0,008 in OD, p= 0,003 in OS) than in group B.VDT use can cause a more significant asthenopia in subjects with uncorrected or inadequately corrected visual acuity (Group B) than in subjects with proper correction (Group A) for all degrees of asthenopia reported except for the highest ( 0= p < 0,00005, 1= p < 0,00005, 2= 0,0006, 3 = no statistic differences).BVCA was the most important factor in reducing asthenopic symptoms of all factors described in our study (hours and year of VDT use, working environment conditions, systemic and ophthalmological history).
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