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1. Nihon Ganka Gakkai Zasshi. 2008 Apr;112(4):376-81.
[Influence of accommodative response and visual symptoms on visual display
terminal adult operators with asthenopia through adequately corrected refractive
errors].
[Article in Japanese]
Kotegawa Y, Hara N, Ono K, Arimoto A, Mukuno K.
Department of Ophthalmology, Kanagawa Dental College Yokohama Dental and Medical
Clinic, Japan.
PURPOSE: Application of adequate correction of refractory errors for the
treatment of asthenopia of young visual display terminal (VDT) workers was
evaluated from subjective complaints and the effect on accommodation dynamics
(step response) before and after 6 months.
METHODS: Young VDT workers who visited the clinic because of eye strain were
consecutively selected. Fifteen workers who were under-corrected for myopia and
three workers who were over-corrected for myopia were treated by "adequate
correction of refractory errors" with spectacles or soft contact lenses. The
adequate correction was defined as minimum convex lenses which could obtain
visual acuity of 1.2 or better, similar to daily life conditions, without
cyclopegia or fogging. The workers were in their 20's. Accommodative responses to
step stimuli were recorded by infrared optometer, and questionnaires were filled
out by the VDT workers concerning the severity (a severity rating in percent in
five steps) of subjective symptoms (headache, dry eye, eye strain, and eye
irritation). Spectacles or disposable contact lenses were prescribed for the
workers for "adequate correction". Six months later, accommodative responses and
subjective symptoms were evaluated and compared with under-or over-corrected
conditions and adequate correction.
RESULTS: In under-corrected workers, the adequate correction significantly
improved complains i.e. headache, eye strain, eye tiredness (p < 0.005).
Accommodative responses also improved in gain (%), maximum velocity (D/sec), and
time of accommodation and relaxation (p < 0.05). Three over-corrected workers
showed improvement of complains and also accommodative response in gain, maximum
velocity, and time of accommodation and relaxation.
CONCLUSIONS: Application of "adequate correction" to young VDT workers with
asthenopia by using adequately corrected spectacles or soft contact lenses
improved the asthenopia and accommodative dynamics.
PMID: 18444417 [PubMed - indexed for MEDLINE]
2. Cont Lens Anterior Eye. 2007 Jul;30(3):174-82. Epub 2007 Feb 12.
Are there differences between 'visual symptoms' and specific ocular symptoms
associated with video display terminal (VDT) use?
Aakre BM, Doughty MJ.
Buskerud University College, Department of Optometry and Visual Science, Frogsvei
41, 3611 Kongsberg, Norway.
Bente.M.Aakre@hibu.no
To assess the reliability of self-reported symptoms of asthenopia associated with
VDT use (as characterized by general visual symptoms, headache and specific
ocular symptoms) for both continuing soft contact lens (SCL) wearers and former
SCL wearers who had undergone successful laser-in-situ-keratomileusis (LASIK)
surgery.METHODS: Forty generally healthy adults, aged between 24 and 44 years,
were asked to complete a 13 page questionnaire that included requests for
information on general visual symptoms, headache and specific ocular symptoms
such as dry eye associated with VDT use. The adults were either long term
successful soft contact lens wearers (n=20) or a similar group who had then
undergone successful LASIK refractive surgery for myopia 2 years prior to the
questionnaire being provided.
RESULTS: Most subjects (70%) reported experiencing some visual symptoms
sometimes, 62.5% reported headaches sometimes, and 82.5 % reported specific
ocular symptoms sometimes. There were no obvious differences between the two
groups either in the reported frequency or severity (by visual analogue scale,
VAS) of visual symptoms, headache or specific ocular symptoms. However, while the
reporting of headache showed no obvious association with the number of specific
ocular symptoms reported, the latter showed a clear correlation with the
reporting of the severity of visual symptoms (p<0.001).
DISCUSSION: The results indicate that when an individual reports visual symptoms,
they may actually be providing recall of specific ocular symptoms. Therefore,
contrary to an often common practice, visual symptoms should be assessed
separately to specific ocular symptoms such that the appropriate management can
be selected. The results also indicate that previous contact lens wearers who
have undergone successful LASIK are still likely to experience some visual and
specific ocular symptoms when undertaking computer based work on a regular basis.
PMID: 17293157 [PubMed - indexed for MEDLINE]
3. G Ital Med Lav Ergon. 2006 Apr-Jun;28(2):207-9.
[Evaluation of myopia in a group of people working with video terminals: first
results].
[Article in Italian]
Basso A, Di Lorenzo L, Cramarossa AA, Corfiati M, Ria W, Bellino R, Crivellini S,
Lofrumento M, Soleo L.
Dipartimento di Medicina Interna e Medicina Pubblica, Sezione di Medicina del
Lavoro EC Vigliani, Università di Bari, Italy.
Since the 70's the occupational use of electronic systems equipped with visual
display terminals (VDTs) became wide-spread also in Italy. Some longitudinal
studies on large samples of VDT workers found no significant changes of myopia
(M) with regard to years and daily hours spent working at a VDT.OBJECTIVE: To
evaluate the prevalence and the time course of M in 209 VDT workers employed in
the service sector.
MATERIALS AND METHODS: After obtaining workers' informed consent their work,
social, family and personal medical histories were collected. Myopia was defined
as need of >0.25 D negative spherical correction. Average daily hours
duringfollow-up and overall years spent working at a VDT were calculated as
exposure indexes.
RESULTS: The mean baseline age was 39.2 years (SD: 8.7, min-max: 22-62) and the
mean education was 14 years (SD: 2.2). The mean follow-up period was 5.5 (3-9)
years. The prevalence of M was 45.5% at the start and 49.8% at the end of the
study. It was higher in workers with >13 years of education and in those < 40
year-old. A slight but significant increase of the degree of M (dioptres)
occurred during the follow-up. The change in the degree of M was not different
between the classes of VDT exposure (< or = 4 and >4 daily hours; < or =15 and
>15 years spent), of education and of age at the end of follow-up.
DISCUSSION: The high mean educational level can partly explain the higher
prevalence of M detected in the workers on study with respect to the one
described elsewhere on VDT workers and general population. The progression of the
M seems not to be related to the professional and personal variables analyzed,
but to depend on the natural evolution of M. Further studies are needed to
confirm these preliminary data in larger groups of VDT workers.
PMID: 16805469 [PubMed - indexed for MEDLINE]
4. Zhonghua Yan Ke Za Zhi. 2005 Nov;41(11):986-9.
[Effects of short-term VDT usage on visual functions].
[Article in Chinese]
Qu XM, Chu RY, Wang L, Yao PJ, Liu JR.
Department of Ophthalmology, Eye Ear Nose & Throat Hospital, Fudan University,
Shanghai 200031, China.
quxiaomei2002@126.com
OBJECTIVE: To evaluate the effects of short-term VDT usage on visual functions.
METHODS: Visual function of the video display terminal (VDT) operators before and
after 1 hour VDT usage were assessed. These included refraction, amplitude of
accommodation, near point of convergence, AC/A, phorias, fusional convergence and
divergence, tear film break time (BUT) and aberrations. And the same situation
was compared was the non-VDT usage.
RESULTS: In comparison with pre-VDT use, amplitude of accommodation, BUT were
significantly decreased (P < 0.05), near point of convergence, near lateral
exophoria were significantly increased after VDT use (P < 0.05). Total, high
order, 4th and 5th order aberrations were significantly greater after VDT use (P
< 0.05).
CONCLUSIONS: Short-term VDT work does have a significantly greater temporarily
effect on visual function, tear film quality and visual quality.
PMID: 16318749 [PubMed - indexed for MEDLINE]
5. Zhonghua Yan Ke Za Zhi. 2005 Nov;41(11):963-5.
[Take high of the study of VDT related eye symptoms].
[Article in Chinese]
Qu XM, Chu RY.
Department of Ophthalmology, Eye Ear Nose & Throat Hospital, Fudan University,
Shanghai 200031, China.
quxiaomei2002@126.com
The characteristics of visual display terminal (VDT) and related eye symptoms
were analyzed. Research of the effect of VDT on visual function, visual
development and characteristics of ocular surface was presented. Currently
research still stays in the initial stage. Intensive research of VDT related eye
problem will provide effective prevention and treatment methods for clinic work.
PMID: 16318743 [PubMed - indexed for MEDLINE]
6. J UOEH. 2001 Dec 1;23(4):345-62.
Survey on occupational health management of VDT workers among 84 Japanese
companies.
Horie S, Ito I, Araki Y, Ohgami A, Hatanaka J, Fujita Y, Shino K, Kikuchi S.
Department of Health Policy and Management, Institute of Industrial Ecological
Sciences, University of Occupational and Environmental Health, Yahatanishi-ku,
Kitakyushu 807-8555, Japan.
This survey of 84 companies described the present status of occupational health
management of VDT workers in Japan, in relation to the official Guideline
(Guidelines on Occupational Health for VDT Work, 1985). The majority admitted 80%
or more of their workers engage in VDT works. Four hours of VDT work per day was
widely used as a criteria for the eligibility to the VDT health examination. Some
specific measurement was performed at health examination among 54.8% of the
companies. The most popular item was "near vision." A larger number of follow-up
measures was performed with ophthalmic cases than with muscloskeletal cases. From
these findings, with consideration to the results of the preceding literatures,
we made 8 suggestions for the on-going revision of the Guideline: 1) including
recommendation for flat panel display and portable computers, 2) widening target
of VDT health education also to general workers, 3) clarification of the
categorization of VDT workers, 4) offering practical measures to secure off VDT
period, 5) use of subjective symptoms to screen high-risk workers, 6) supply of
the latest scientific information on each measuring item, 7) periodical revision
to provide state-of-the-art management, and 8) clear statement of the purpose and
limitation of the Guideline.
PMID: 11789137 [PubMed - indexed for MEDLINE]
7. Acta Ophthalmol Scand. 2000 Feb;78(1):26-9.
The influence of near-work on development of myopia among university students. A
three-year longitudinal study among engineering students in Norway.
Kinge B, Midelfart A, Jacobsen G, Rystad J.
Department of Ophthalmology, Norwegian University of Science and Technology,
Trondheim.
bkinge@online.no
PURPOSE: The aim of this study was to investigate the effect of near-work on
development and progression of myopia among adults exposed to high educational
demands.
METHODS: A three-year longitudinal refraction study was performed among 224
Norwegian engineering students (mean age 20.6 years, 117 females and 107 males)
measuring their refraction at the beginning and the end of the period. The
examinations included automated and clinical refraction in cycloplegia and a
questionnaire regarding time spent on different kinds of near-work was filled in
by the participants. A total of 192 students (100 females and 92 males) completed
the study.
RESULTS: The mean refractive change of -0.51+/-0.49 D (n=192) during the
three-year period was statistically significant (p=0.0001). A significant
relationship between refractive change towards myopia and time spent on reading
scientific literature (p< or =0.001) and on practical near-work (p< or =0.05),
respectively, was found. Also, a significant relationship between refractive
change towards myopia and time spent at lectures was revealed (p< or =0.001). No
relationship was found between refractive change and time spent at working with
video display terminals (VDT) or watching television, respectively.
CONCLUSIONS: The results indicate that intensive near-work could initiate myopia
or lead to its progression in young adults. The time spent on near-work seems to
play a significant role in that process.
PMID: 10726783 [PubMed - indexed for MEDLINE]
8. J Am Optom Assoc. 1996 Sep;67(9):521-30.
Is computer use a risk factor for myopia?
Mutti DO, Zadnik K.
School of Optometry, University of California, Berkeley 94270-2020, USA.
BACKGROUND: Many patients who become myopic or who undergo increases in myopia as
adults have concerns about whether the use of video display terminals (VDTs)
contributes to these changes in refractive error. This paper is an overview of
the current literature on topics concerning VDTs and factors related to proposed
etiologies for myopia.
METHODS: Selected literature is reviewed on the relationship between VDTs and
asthenopia, fatigue, accommodation, and vergence. Clinical studies of myopic
progression and transient myopia among VDT users are considered, as is television
viewing as a risk factor for juvenile myopia.
RESULTS/CONCLUSIONS: Reports of asthenopia are common with VDT use by a factor of
1.4 to 1.5, compared to conventional office work. Questions of comparability
remain between VDT users and nonusers with respect to confounding variables such
as the number of work hours. Proofreading on a VDT appears to be less efficient
than using printed copy. Despite screen flicker and reflections, the
accommodative response appears to be accurate to a VDT. Transient,
fatigue-induced changes in accommodation and vergence may occur after work with
VDTs. Despite these near point changes, there is no compelling evidence in the
literature that suggests there is a significant increase in the risk of myopia
onset or progression from the use of VDTs by adults compared to other forms of
near work.
PMID: 8888885 [PubMed - indexed for MEDLINE]
9. Ophthalmologe. 1994 Feb;91(1):103-6.
[Evaluation of refractive values in patients working for several years at video
display terminals. A long-term study].
[Article in German]
Toppel L, Neuber M.
Augenklinik rechts der Isar TU München.
The authors discuss whether working at a VDT (video display terminal) over a
period of years causes non-reversible changes in refraction, especially if it
induces a drift towards myopia. A total of 107 persons who had been working at
VDT for many years were examined at 2-year intervals and the observations
compared with those recorded in 69 persons who had never worked at a VDT. Changes
in the correction strengths of their spectacles were evaluated. The statistical
analysis was done by chi-square value determination and the Mann-Whitney U-test.
The special lens values (diopters) showed no significantly different development
in the two groups. It can therefore be concluded that VDT work does not cause
myopia to worsen. The cylindrical lens values on the other hand differed
significantly in the two groups. This is most probably because any inadequacy in
the correction of visual acuity will be noted more easily by persons involved in
VDT work.
PMID: 8173241 [PubMed - indexed for MEDLINE]
10. Appl Ergon. 1993 Oct;24(5):327-36.
Effectiveness of the C-Sharp: reducing ergonomics problems at VDTs.
Gallimore JJ, Brown ME.
Wright State University, Department of Biomedical and Human Factors Engineering,
Dayton OH 45435, USA.
The use of visual display terminals (VDTs) has been associated with complaints of
visual fatigue and body discomfort. In an effort to eliminate some of these
problems, an ergonomic emphasis has been placed on the design of computer
workstations. A new device, the C-Sharp, has been developed to

reduce some
of the ergonomics problems related to long-term VDT usage. The C-Sharp was
designed to alleviate visual strain and temporary myopia by reducing the amount
of muscular work associated with accommodation and convergence to near targets.
It was also designed to eliminate glare. The present study is an ergonomics
evaluation to determine whether the C-Sharp meets accepted standards and
guidelines. Specifically, the objectives of the research are to determine the
effects of the C-Sharp on operator reading and search performance, perceived
comfort, body posture, and visual acuity. The C-Sharp is compared with mesh-glare
filter and no-glare filter device conditions. Subjects were blocked into three
groups based on age and type of vision correction (with or without bifocals).
Results indicate that the C-Sharp meets the recommendations of the Americal
National Standard for human factors engineering of visual display terminal
workstations. No differences in objective performance were found between the
three glare device conditions. The C-Sharp allowed bifocal wearers to keep their
necks in natural postures rather than tilted backwards. Post-session far visual
acuity worsened regardless of the device condition.
PMID: 15676929 [PubMed]
11. Ind Health. 1993;31(1):13-28.
Visual comfort in VDT operation: physiological resting states of the eye.
Taptagaporn S, Saito S.
Department of Public Health and Environmental Science, Tokyo Medical and Dental
University, Japan.
To recommend a comfortable visual display terminal (VDT) workstation design in an
aspect of visual ergonomics, physiological resting states of the eye in 3 visual
systems, pupil, vergence, and accommodation, were objectively investigated in 3
experiments. Experiment 1 ascertained a positive display polarity (dark
characters on a bright background) and an illumination level of 500 lx to be the
most appropriate working conditions, by using pupil analysis and subjective
visual comfort in 10 subjects. Dark vergence, in experiment 2, was evaluated to
be at a distance of about 50 cm from the eye, as an average in 14 subjects. Dark
vergence was found to shift farther with an upward gaze while a nearer shift
occurred with a downward gaze. In experiment 3, the average dark focus for 11
subjects was found to be 1.4 diopters (D) or a distance of about 74 cm from the
eye. The positive correlation between refractive status of the eye and dark focus
was statistically significant (r = 0.602). The ergonomic recommendations for a
VDT workstation obtained in this study are a positive display polarity with an
appropriate lighting condition, a downward gaze, and a viewing distance between
50 and 70 cm. These recommendations are considered to reduce visual fatigue due
to prolonged VDT work and to facilitate visual comfort at work.
PMID: 8340226 [PubMed - indexed for MEDLINE]
12. J Hum Ergol (Tokyo). 1992 Jun;21(1):13-20.
Time factors in VDT-induced myopia and visual fatigue: an experimental study.
Watten RG, Lie I.
Vision Laboratory, University of Oslo, Norway.
In an experimental design with two matched groups (n = 13 and n = 17) working 2
and 4 hr respectively, followed by a 15-min restitution time, the study examined
the effect of continuous VDT work on 1) visual acuity, refraction and oculomotor
functions (ZCSV: zone of clear, single vision) and 2) the effect of 15-min
restitution time on the oculomotor functions (ZCSV). In both groups there were a
significant reduction in visual acuity, refraction changes in myopic direction
and reduced ciliar and vergence muscle capacity. The ZCSV changes were temporary
and a 15-min restitution period restored approximately half of the ZCSV changes.
There were no significant differences between 2 or 4 hr of VDT work on any of the
variables examined.
PMID: 1491167 [PubMed - indexed for MEDLINE]
13. G Ital Med Lav. 1989 Nov;11(6):267-71.
[Asthenopia and objective ophthalmological findings in a population of 2058 VDT
operators in Lombardy].
[Article in Italian]
Piccoli B, Gratton I, Pierini F, Catenacci G, Raimondi E, Farulla A.
Istituto di medicina del lavoro, Clinica del lavoro L. Devoto, Università di
Milano.
A large population of 2058 VDT operators from all compartments in Lombardia of a
large national company was studied. An "ergophthalmological" questionnaire was
administered to all subjects, followed by an ophthalmological-orthoptic
examination. Ametropias showed a prevalence of 51.9%; the most common refractive
defect was myopia followed by astigmatism and hyperopia. Heterophorias with bad
or mediocre compensation had a prevalence of 4.1 and 11% respectively. The study
of symptoms showed a frequency of 23.5% of intense asthenopic complaints and
21.1% of less severe and less frequent symptomatology. Asthenopia was
significantly correlated (chi square) with sex, VDT exposure, refraction,
presbyopia, and decompensated heterophorias.
PMID: 2562747 [PubMed - indexed for MEDLINE]
14. Med Lav. 1989 Mar-Apr;80(2):155-63.
[Temporary myopia and subjective symptoms in video display terminal operators].
[Article in Italian]
Luberto F, Gobba F, Broglia A.
The study covered a group of female VDT operators assigned to data entry and data
acquisition. Subjective VDT-related symptoms of asthenopia were assessed by means
of a questionnaire. All operators were examined by an ophthalmologist. Visual
acuity was measured using vision tables with optotypes. In order to achieve an
objective assessment of VDT-induced visual fatigue, refractive power was measured
at the beginning and at the end of the shift, using an infra-red
autorefractometer. Changes in refractive power were then related to VDT work and
asthenopia symptoms. Visual acuity defects were observed in 63.5% of the
operators; in 36% of the cases the subjects were either unaware of the defects or
the defects were not adequately corrected. 62.5% of the operators complained of
subjective asthenopia symptoms. Asthenopia was not related to the number of hours
at the VDT. The results suggest that ametropic subjects are likely to be more
susceptible to visual fatigue than emmetropic subjects, since there was a
tendency for the prevalence of asthenopia to increase in the former group. A
significant decrease in refractive power (temporary myopization) was observed in
20% of the operators at the end of the shift at the VDT: all these subjects also
complained of asthenopia, compared to 50% of the workers without end-of-shift
myopization. The difference between the groups was highly significant (p less
than 0.01); contrarywise, none of the subjects without asthenopia developed
myopization. On the basis of these results, it can be concluded that end-of-shift
myopization, as measured by an automatic refractometer, may be used as a reliable
objective measurement of VDT-related visual fatigue.
PMID: 2770619 [PubMed - indexed for MEDLINE]
15. Sangyo Igaku. 1989 Jan;31(1):24-5.
[A case of rapidly developed myopia among VDT-workers].
[Article in Japanese]
Yoshikawa H, Hara I.
Department of Public Health, Kansai Medical University, Osaka, Japan.
PMID: 2739099 [PubMed - indexed for MEDLINE]
16. Int Arch Occup Environ Health. 1988;60(2):81-7.
Visual fatigue in video display terminal operators: objective measure and
relation to environmental conditions.
Gobba FM, Broglia A, Sarti R, Luberto F, Cavalleri A.
Cattedra di Medicina del Lavoro, University of Modena, Italy.
The lighting conditions, luminance, contrast, and design of the workplace were
studied in video display terminal (VDT) work stations operated by a group of
female VDT data-acquisition clerks. VDT-induced symptoms were assessed by means
of subject answers to a questionnaire. To measure VDT-induced ocular fatigue
objectively, refraction power was determined before and at the end of workshift
by an infrared autorefractometer. Job-induced refraction changes were then
related to visual complaints and conditions in the workplace. The results
confirmed that VDT data-acquisition work can lead to temporary myopia
(myopization) in a remarkable percentage of operators; a significant correlation
between eye discomfort, ocular asthenopia, and myopization was also found.
Illumination levels, luminance, and contrast seem to be of paramount importance
regarding visual symptoms: neither asthenopia nor myopization was observed when
all of these conditions were adequate. If the ergonomic design of the workplace
and the viewing distance are adequate, there are also usually fewer
musculoskeletal symptoms. Our results suggest that changes in the ocular
refraction status before and at the end of the work-shift, as determined by an
automatic refractometer, provide a good objective index of VDT-induced "ocular
fatigue", which in our study proved to be significantly related to workplace
conditions.
PMID: 3346085 [PubMed - indexed for MEDLINE]
17. Acta Ophthalmol Suppl. 1988;185:172-4.
Effect of visual display terminal (VDT) work on myopia progression.
Tokoro T.
Eye Department, Tokyo Medical and Dental University, Japan.
PMID: 2853531 [PubMed - indexed for MEDLINE]
18. Scand J Work Environ Health. 1985 Dec;11(6):483-7.
Work with video display terminals among office employees. IV. Refraction,
accommodation, convergence and binocular vision.
Nyman KG, Knave BG, Voss M.
The present study is the fourth of a major epidemiologic health investigation on
work with a video display terminal (VDT). The other studies showed that VDT
operators replying to questionnaires have more eye discomfort than a reference
group of office employees not employed in VDT work and that women have more eye
discomfort, musculoskeletal complaints, headache, and skin disorders than men.
Routine ophthalmologic examinations failed to establish any appreciable
differences between the groups; for example, the prevalence of myopia was the
same. In the present study, the VDT operators and referents were examined before
and at the end of work sessions for changes in refraction, accommodation,
convergence capacity, and binocular vision such as heterophoria and fusion range.
No differences could be established between the VDT operators and the referents.
PMID: 4095526 [PubMed - indexed for MEDLINE]
Saludos