1.
As technology advances, eye strain and other symptoms of asthenopia are on the rise.
By Dominick M. Maino, O.D., M.Ed., and Christopher Chase, Ph.D.
V
ision systems evolve over ~m1.S~~lafAsthenopia
generations based on the
needs of the users and the nodifidhomPdlA CipbnMe CIrnicid PM'W b~delim)
environment. In humans,
evolutionary pressures led to the
development of the need for clear
distance visual acuity and binocu-
lar three-dimensional (3D) stereo-
scopic vision. These visual skills
enabled us to effectively respond
to threats in the environment
that were distant and constantly 5?
changing, and improved our 4 Photophobia
odds of being the hunter rather
than the hunted.' When Johannes
Gutenberg developed the process
for modern book printing in the
mid 15th century, he set in mo-
tion the shift in visual demands
away from the importance of see- @ Rwninghealng o
-
f , . .
ing clearly at distance and toward
a time intensive two-dimensional
near-point task such as reading.2 D i i u l l y reading
The emergence of mass-
produced print materials, such
as books and newspapers, has
resulted in patients experienc- Poor concentration
ing eye strain, and for some
individuals, resulted in academic basis, with potentially serious advances in these devices result
and work limitation^.^^^ As tech- health implications.' This problem in viewing screens of diminish-
nology advanced and electronic will continue to grow in scope as ing size. For example, films that
media became more dominant, patients spend increasing amounts were once projected onto a screen
eye strain has progressed to a of time performing near-vision that spanned the width of a wall
problem encountered on a daily tasks via digital media and as a n now be viewed on a handheld
98 REVIEW OF OPTOMETRY JUNE 15. 201 1
Y

2.
screen that is a mere 2" x 3." The IFigure 2. Etiology of Asthenopia I
-
(AOA Optornetr~c Pract~ce
Ci~n~cal Guidl~ne)
technology-induced visual impair-
ments we are witnessing today are
the result of our vision informa- .' ,+I
.,:..
n..-5,
Accommod,,
.
1
I
7-Accommoc,..,
I ,,..,.-.,.,,.,..,.,.,..,
Specific Diagnostic Categorical Descriptions
tion processing system attempting 3
to undo a millennia of evolution Insufficiency than expected for patient age <x z
.:j
and adjust to a relatively sudden Ill-Sustained Amplitude of accommodation is normal, but fatiguc
change in the demands placed Accommodation occurs with repeated accommodativestimulation
upon our vision.
Asthenopia, which includes eye Accommodative The accommodativesystem is slow in making et
'
strain and several other symp- Infacility change or when there is considerable lag between ,
toms (figure I ) , often occurs in the accommodativestimulus and the response
patients whose visual systems Vergence Paralysis of Accommodative system fails to respondto any
are capable of performing near- Accommodation stimuli (very rare)
vision tasks for limited durations
of time. It should be noted that
3
I
Spasm of
Accommodation
Results from overstimulation of the parasympathet$Bd
nervous system 1@
asthenopia does not occur as a
consequence of any weakness
within the ocular musculature sys-
4 Vergence
Dysfunction
. , .., , - ;
i
*Convergence Insufficiency: consists of a receda
near point of convergence, exophoria at near, .
reduced positivefusional convergence, and defi-
tem, but rather from the sustained ciencies in negative relative accommodation
near point demands now placed *Divergence Excess: exophoria or exotropia at far
upon a visual system primarily greater than the near deviation by at least 10 prism
designed for distance tasks. This diopters
is frequently caused by a lack of @Basic Exophoria: having a deviation of similar
appropriate cortical output that magnitude at both distance and near
is necessary for accurate accom- *Convergence Excess: having near deviation at
modative and fusional vergence least 3 prism diopbrs more esophoric than the dis,
system responses, and for the tance deviation
demands of the task.' As seen in *Divergence Insufficiency:tonic esophoria is high
figure 2, there are a number of when measured at d i i c e but less at near
etiologies for asthenopia, but a *Basic Esophoria: High tonic esophoria at distance
recent study of 30 to 40 year-old a similar degree of esophoria at near, and a norma
myopic subjects with asthenopia .< accommodativeconvergence/accommodation
(N=253)found that the most fre- 4. -.
! (AC/A)ratio
quently encountered oculo-visual s-'
*Fusional Vergence Dysfunction: having normal
problem was ill-sustained accom- '
.i .n
.a phorias and AC/A ratios, but reduced fusional ver-
modation (54%).'p5 These findings gence amplitudes
corresponded with a 2001 study @VerticalPhorias: these may be either comitant and
of 18 to 38 year-old subjects that idiopathic or noncomitant, due to muscle paresis 9,
reported accommodative disorders other mechanical causes
in 61% of s ~ b j e c t s . ~ - --
&
How Prevalent Is underestimated; 2) Patients expe- formed while wearing spectacles
Asthenopia? riencing these symptoms may not or contact lenses.
Gauging the prevalence of this always schedule an examination Research by Sheedy and associ-
disorder has proven difficult for or report them while being exam- ates shows two different afferent
three reasons: 1)If only one or ined due to the perception that pathways for the symptoms of
two symptoms of a wide-ranging no treatment options exist; and asthenopia. The symptoms can
symptomatology are assessed, 3 ) Patients may perceive these be divided into associations with
then the frequency and impact symptoms as an expected result either external or internal factors.
of asthenopia are bound to be associated with the near task per- External symptom factors (burn-
REVIEW OF OPTOMETRY JUNE 15, 201 1 29

3.
ing, irritation, tearing and
dryness) are related to dry
eye while internal symptom
factors (ache, strain and
Symptom (NSIGHT 2009) -
Figure 3: Percentage of Patlents Expdgnclng Particular Asthenoplc
headache behind the eyes)
are related t o accommoda-
tive or binocular vision
stress.'
A study was conducted
that included 3,800 vision-
corrected (contact lenses
or spectacles) patients
from China, Japan, Korea,
France, Italy, the United
Kingdom and the United ,_-..u'n . -- , Hea--..- ....~r Near Fain lnslae the E,-
States that allowed for the Work
determination of the preva-
"N = 3800 viaionconsctedpatients (Chine, Japen, Koree, Frence, Italy, UY USA).
lence, frequency and impact
of asthenopia upon the indi-
~ i d u a lThe next set of four
.~
figures show the findings from and pain in the eyes, occurred in the ages of 10 and 39, when the
this study. Figure 3 shows the fewer respondents than the other amount of near work is great-
percentage of patients experienc- symptoms listed, but high percent- est.' Many individuals with
ing symptoms. Figure 4 identifies ages of these respondents tended chronic problems have learned
the symptoms by region. Figure to experience these symptoms at to live with their condition and
5 pinpoints the symptoms expe- least three times or more each may not voluntarily reveal their
rienced three to seven times each week (headaches after near work symptoms. Young children (pre-
week. And, figure 6 highlights the 42%; pain inside the eye 33%) school and early grades) may have
negative impact of symptoms. (figure 5). Not surprisingly, a fewer near-vision demands; more
Results show that patients fre- pain-related symptom had the importantly, many children no
quently experienced asthenopic highest percentage of patients matter their age are often unable
symptoms with as many as 58% who found their occurrence to to describe their symptoms. These
experiencing eye strain and 69% be very bothersome (headaches children often do not report the
tired eyes (figure 3 ) . Many of the after near work, 44%), which was symptoms associated with asthe-
symptoms that involved a pain- almost twice as high as the next nopia because they consider them
ful sequelae, such as headache ~ y m p t o mThis 3,800-patient
.~ as being what is normally experi-
after near work and pain inside survey shows that a large number enced by all.'
the eye, occurred less frequently of patients suffer from asthenopia Those whose occupations
but still affected 29% and 19% and the associated symptoms are require considerable amounts of
of patients, respectively (figure experienced repeatedly during the close work are at an especially
3). Patients from Asia demon- week and have a negative effect high risk. Studies have noted that
strated the greatest propensity on the individual's quality of life. computer operators are particu-
for all symptoms of asthenopia larly susceptible to asthenopia
(figure 4). These data suggest that Which-PatientsAre At because a high percentage of com-
the symptoms of asthenopia are Greatest Risk? puter users with symptoms have
prevalent and that practitioners All patients are at risk for binocular vision problems and
should be proactively inquiring if developing asthenopia, but the ocular discomfort increases with
their patients are experiencing any extent of that risk varies from the extent of computer u ~ e . ~ - ' ~
of these symptom^.^ individual to individual. Most In a study of 419 computer
Pain-related symptoms, such patients report symptoms of operators in India, 46% suffered
as headaches after near work vergence dysfunction between from asthenopia during or after
30 REVIEW OF OPTOMETRY JUNE 15. 201 1

4.
Visual
computer at work. Some
Figure 6: Percentage of Patiants* Who Found Thelr Asthenopic
occupations have a greater
Symptoms to be BoUlersome (NSIGHTPWS)
proportion of computer
users, with the rates for
100 -
managers (about 80%) and I
salesloffice workers (67%) 80 i
being particularly high.21
Additionally, 77% of those , ,b
*, 60 1
working from home were
computer users as
(%) 40
I,
I
Computer use is not the 20 1
only source of demanding - I
0 .I-.
near-vision tasks. Reading of
Eye Strain Tired Eyes Headache After Pain Inside the Eye
work-related printed mate Near Work
rials can also significantly
mSligMly bothersome -Very bothersome
contribute to the stressors
placed upon the vision sys w = 3800visiarrmncctad patianla (China,Japan, Koree, F m , Italy, UK USA).
tem.
An overabundance of
work-related near-vision tasks is companies add 3D capabilities to of vision correction in the past
not the only reason why astheno- their products, video game play- can experience discomfort while
pia is increasing in our patients. ing is also becoming a significant watching 3D." In one study of
The use of various electronic contributor to the amount of time young adults with normal binocu-
media, including cell phones, elec- spent viewing images in 3D.25It lar vision, almost half experienced
tronic messaging and texting, the should be noted that the Nintendo significant visual fatigue and dis-
Internet, standard high definition 3DS system is a handheld device, comfort while viewing 3D.28The
and 3D televisions, and 3D mov- forcing users to view 3D images American Optometric Associa-
ies and video games, increases the on a very small visually demand- tion estimates that between three
demands placed upon an already ing screen.2s and nine million (and possibly
taxed vision system. Figure 7 lists Three-dimensional viewing more) Americans have problems
useful statistics on the inroads contributes an additional level of appreciating the 3D e x p e r i e n ~ e . ~ ~
that these electronic media have burden to the overload of near- With an increase in these visually
made into peoples' daily lives. vision tasks that visual systems demanding tasks, not only will
are already struggling to perform. the time spent performing vision-
The Future Is Now: 30 Individuals who have poor con- intensive activities continue to
With the success of the 3D film vergence, accommodation, and add stress to our work day and
Avatar and the development of visual tracking abilities-all of recreational activities, it will also
3D television and video games, which are necessary for single, require greater effort on our part
exposure to this form of entertain- clear and comfortable 3D view- to appreciate these many new and
ment is expected to increase in the ing-may experience blurred quality of life-changing technolo-
near future. In 2010, more than vision, diplopia, dizziness and gies.
20 3D feature films were released. headaches when exposed to this
ESPN is already providing pro- type of media. Consequences of Asthenopia
gramming in 3D (e.g., 18 World Only now are we beginning Asthenopia often includes
Cup matches), and the Discovery to study those who experience health-related consequences such
Network will launch its own symptoms while viewing 3D as headache, diplopia, pain in
3D channel in 2011.U In 2010, content. Patients with this newly and around the eyes and overall
DirecTV began offering its sub- coined "3D Vision Syndrome" feelings of fatigue (figure 1). A
scribers three channels dedicated require further clinical interven- person's quality of life can be
to 3D.24 tion and research.26Even patients reduced as the pain and discom-
As Sony, Nintendo and other who haven't required any kind fort associated with accomplish-
32 REVIEW OF OPTOMETRY JUNE 15, 201 1

5.
j Internet Approximately 80% of Americans have accegs to the Internet" Internet use is not the domain
of only the young, as 40% of Americans over the age o 66 years use it.' Inthe US., an aver-
f
age of 17 hours per week is spent looking at the Internet, with 2.8 hourslweek for light users
and 42 hourslweek for heavy users." Over the last 10 years, Internet use has grown by 444%
globally, with the largest increases in Africa (2357%). Middle East (1825%), and Latin America1
Caribbean (1032%)."
Electronic messaging Over 1billion texts and 247 billion e-mails are sent daily.474
%ll Phone Americans use their cell phones an average of 21 minuteslday. Thirty-five percent of &-r--.
OMSin the U.S. own a cell phonema Internet access via cell phone Increases a n n ~ a l l y&~
j
.:
,
. 1
:1.-11
The top five countries with the most cell phones are: China (824.3 million), India (687.7 milt -..
lion), U.S. (285.6 million), Russia (213.9 million) and Brazil (194.4 million). The top five coun-
tries with the highest percentageof cell phones per capita are: Russia (147%), Germany
(130%), United Kingdom (123%). Ukraine (118'??) and Spain (111%).5081
I
Smart phones are the next stage of development of cell phones. Thii newest-generation o f
phone is evolving into a handheld computer that can also make phone calls. The amount
of programs (or apps) continues to grow, exponentially expanding the number of uses and
resulting in increased time using them. There are tens of thousands of apps availablefor
Android phones and more than300,000 for the iPhone.
ing particular activities can lead Practitioners need to be proactive point activities. If the practitioner
to patients no longer performing in determining the full extent of is not comfortable testing for
them. Hayes and associates found their patient's near-vision activi- binocular disorders or in provid-
a small but significant relationship ties. It is also important to ask ing optometric vision therapy,
between ocular symptoms and appropriate questions regarding the patient should be referred
global measures of quality of life any asthenopic symptoms typi- to an eye care practitioner who
and a large association between cally associated with binocular is.63Such practitioners have been
eye and physical symptoms.30 vision dysfunction. Because the certified by the College of Optom-
Symptoms associated with asthe- patient may not realize that etrists in Vision Development (an
nopia not only negatively affect not everyone sees the same way international organization) and
a person's productivity and aca- they d o and that what they are can be found by logging on to
demic performance, but also our experiencing is not normal, only www.covd.o~.
ability to perform work-related a carefully taken case history All patients can be at risk for
and recreational tasks in an effi- can discover the problems your developing asthenopia, so prac-
cient and comfortable manner.' patients may have in this area. titioners should educate them on
Answers received from the patient what it is and how it may develop.
Treatment of Asthenopia should then be reviewed together For those patients with a greater
Treatments for asthenopia are so it is clear that you and the risk for asthenopia based on their
available, but as with any health patient are using the same words visual demands, information
problem, the first step is diagno- to define the same thing^.^^,^^ should be provided concerning
sis. The simplest way to assess A comprehensive assessment of visual hygiene and various meth-
the presense of asthenopia due the individual's binocular vision ods for modifying their near view-
to internal factors is to stress the system should be conducted for ing environment. Practitioners
accommodative and vergence sys- patients experiencing adverse should advise their at-risk patients
tems during your examination.' reactions when performing near- to d o the f o l l o ~ i n g : ~ ~ - ~ ~
REVIEW OF OPTOMETRY JUNE 15. 201 1 a

6.
When performing computer Vision therapy helps the patient are dominant. This relatively
work, schedule periodic breaks to develop efficient visual skills new vision demand will con-
where they look away from the and vision information process- tinue to develop in magnitude as
monitor (generally for every 20 ing. The therapeutic procedures the time spent performing near
minutes of computer use have re-educate the brain so that the tasks increases and as the size
them look away for 20 seconds). individual can achieve single, of electronic displays continue
Make sure there is proper clear, comfortable, binocular to decrease. The inclusion of 3D
lighting for performing near-point vision that improves eye coordina- viewing technologies only further
tasks. tion, focusing and eye movement, complicates the problem.
Use proper ergonomics at the which ultimately enhances the As a large proportion of
workstation. 3D viewing e x p e r i e n ~ e . ~Stud-
'-~~ patients are candidates for devel-
Use a larger font for onscreen ies have shown that office-based oping asthenopia, practitioners
text. treatment (in addition to home- need to determine their level of
Blink often. based activities) is efficacious and risk by asking appropriate ques-
Practitioners can also advise long la~ting.~~dO In these studies, tions about their occupations,
the patient that specially designed vision therapy intervention not the activities they pursue in their
near-point corrective lenses can only eliminated symptoms, but free time, and the amount of time
help relieve the symptoms associ- also improved functional abili- they spend performing near-point
ated with asthenopia. Strategies ties-both accommodation and tasks. Practitioners also need
specific to computer operators vergence. These remarkable to educate their patients about
should also be employed to reduce results lasted at least 12 months ways they can reduce their risk
the incidence of asthenopia. In a post intervention. For patients of developing asthenopia, such as
study by Kotegawa and associ- who cannot attend in-office by taking periodic breaks from
ates, computer operators (20-29 weekly vision therapy appoint- watching a computer screen and
years of age) who had originally ments, out-of-office therapy using paying attention to the ergonom-
been undercorrected or overcor- computer programs to improve ics of their workstation. The use
rected experienced a reduction in vision function are also effec- of corrective and therapeutic
headache, eye strain and tired eyes tive.26,39.41 lenses will often help to relieve
after receiving accurate refractive Non-presbyopic patients, who symptoms while implementing an
c ~ r r e c t i o nThe use of antireflec-
.~~ are otherwise healthy but have individually prescribed program
tive film on monitors and the use accommodative insufficiency, of optometric vision therapy can
of certain colors (e.g., blue and can benefit from using multifocal frequently completely eliminate
white rather than green and red) spectacles to reduce the astheno- the asthenopia.
have also been shown to reduce pia associated with this focusing Asthenopia is a frequently
the incidence of asthenopia in d y s f ~ n c t i o n . Because some
~~-~~ encountered visual impairment
some computer adult contact lenses wearers that can seriously threaten a
Asthenopia can be successfully exhibit decreased accommoda- patient's quality of life. It inter-
treated with vision therapy. The tive abilities, consider using either feres with the quality of our work,
goals of vision therapy are to near reading prescriptions in our performance in school and
ensure that the patient can visu- conjunction with the single vision our enjoyment at play. Astheno-
ally function efficiently and com- contact lenses or multifocal con- pia is a prevalent condition that
fortably in school, at work andlor tact lenses if asthenopia develops deserves our full attention so
in athletic activities, as well as to for these patients.44 that, once diagnosed and treated,
relieve any symptoms. For accom- patients can pursue their interests
modative therapy, treatment Conclusions to the best of their abilities with-
increases the amplitude, speed, The world where people needed out experiencing pain or discom-
accuracy and ease of the focusing the ability to respond to stimuli fort.
response. At the end of therapy, that were distant, potentially
the patient should be able to make dangerous and constantly chang- Disclosure: Editorial assistance
rapid and accurate accommoda- ing has been replaced with one provided by BioScience Commu-
tive responses without fatigue. where sustained near-point tasks nications.
94 REVIEW OF OPTOMETRY JUNE 15. 201 1

7.
1. American Optometric Association Consensus Panel on makes some people sick. Washington Post. July 6, 2010. Ophthalmol Strabismus. 1988 Jul-Aug;25(4):176-9.
Care of the Patient with Accommodative or Vergence Dys- Available al: mm.washinatonoosl.com/wo-dvn/contenv 43. Wahlbera M. Abdi S. Brautaset R.Treatment ol
function. Dptometric Clinical PracticeGuideline: Care of p Accessed , accommodakve'insufficikncy with plus lens reading addi-
the Patient with Accommodative and Vergence Dyslunction. September 13,2010. tion: is +I D better than t2.00 D? Strabismus. 2010
.O
O
St. Louis, MO; American Optometric Association: 2006. 24. Gustalson R. Parentinoand the media: 3D TV is Jun;18(2):67-71.
2. Britannia Online Encvclooedia. Johannes Gutenbero here, but is it harmlul to young eyes? Available at:
. . 44. Jimnez R, Martinez-Almeida L, Salas C, Ortlz C. Con-
(German Printer). ~vailable www.britannica.rom/
at: - ~ n s / r m I ~ O l O l 0 4 2 8 tact ~ . lenses vs spectacles in myopes: is there any dihrence
EBcheckadRooicn49B78/Johannes-Gutenbera.Accessed Accessed September 29.2010. in accommodative and binocular function? Graefes Arch
Dctober 6.2010. 25. Stiles L. The oame chanoer: Plavstationooes 30. Mav
- . Clin Exp Ophthalmol. 2010 Nov 23. [Epub ahead of print]
3. M~~OW'ML, TD, FinjkelmanS, et al. Acute
France 6,2010. ~ v a i ~ aat: ~ i
b . 45. The Center lor the Digital Future. 2008 USC Annenberg
accommodativeand convergence insufficiency. Trans Am 3 d - O a a . Accessed Digital Future Study. T e Center lor the Digital Future. USC
h
Ophthalmol Soc. 1989;87:15&173. September 29,2010. - Annenberg School for Communication.2008. Available at:
..
4. Sauter S. Chaoman LJ. Knutson SJ. lmorovino VDT 26. Maino 0. The 3 D Vision Syndrome: A Case Report. www.dloltalcenter.ora/odW201-dioital-luture-reoort-1inal-
Work: causes i d control ol Health concerns ~ ~ V Use. DT Abstract presented at: Annual Meeting of the American release.odr. Accessed September 9,2010.
Madison, WI: Dept of Preventative Medicine, University of Academy ol Optometry; November 17-20.2010; San 46. Miniwatts Marketing Group. Internet usage statistics:
Wisconsin. 1984 Francisco. CA. the lnternet big picture. Available at: www.lnternetworld-
5. Reindel WT. Cairns G. Zhano L. Bateman K. Evaluation 27. The Wall Street Journal. Vision disorder makes 3-D fall w. Accessed December 13,2010.
of Binocular Function &ong freharly PresbyopesWith flat for some. The Wall Street Journal. May 18,2010. .Avail-
. 47. Cell phones key to teens'social lives. 47% mn texl
Asthenopia. Poster presented at: Annual Meeting of the able at: p eyes closed. Available at:
. with
-
~merican Academy of Optometry; November 17120,2010; r-
e. Accessed September 29,2010.
San Francisco, CA. 28. Holfman OM, GirshickAR, Akeley K, Banks MS. Ver- .- Accessed May 24,2010.
6. Monles-Mico R. Prevalenceof general dyslunctionsin gence-accommodation conflicls hinder visual performance 48. RadicatiTeam. E-mail Statistics Report, 20042013.
. .
binocular vision. Ann Ophthalmol. 2001;33:205-208. and cause visual fatigue. J Vision. 2008;8:1-30. .
Available at: www.radlcall.comRo-3237Accessed May
7. Sheedy JE, Hayes J, Engle J. Is all asthenopia the same? 29. American Ootometric Association. 3-0 TV and Movies 24.2010.
Optom Vis Sci. 2003;80:732-739. Look to Attract viewers but not Everyone can 'See' What All 49: Cellphone.org. Interesting stats on cell phones. Avail-
8. Needs, Symptoms, Incidence, Global Eye Health Trends the Hype Is About. Available at: www.aoa.oro/xl5123.wnl.
. -
able at:
(NSIGHT) Study. Market Probe Europe: December 2009. Accessed September 13,2010. cell-ohones/.Accessed October 6,2010.
9. Sheedy JE, Parsons SD. The video display terminal eye 30. Hayes JR, Sheedy JE, Stelmack JA, Heaney CA. Com- 50. List ol countries by number of mobilephones in use.
clinic: clinical report. Optom Vis Sci. 1990;67:622-626. puter use, symptoms, and quality of life. Optom Vis Sci. Available at:
10. Berqvist UO, Knave BG. Eye discomfort and work with 2007;84:E739-E745. mber of mobile ohones in m.Accessed
visual display terminals. Scand J Work Environ Health. 31. Maino DM. ldentifv binocular vision disorders. Ooto- December 13.2010.
1994;20:27-33. metric Management, december 2009. Available at: & 51. Cellur-news.com. Vodalone sees loss of UK market
11. Neugebauer 4 Fricke J, Russman W. Asthenopia: ootomelric.com/artlcle.asorlatlicle.l.
~. Accessed share and lower ARPUs. Available at: www.cellular-naws,
frequency and objective findings. Ger J Ophthalmol. September 29,2010. Accessed December 28,2010.
1992;2:122-124. 32. American Optometric Association. Healthy Vision on 52. CTlA - The W i r e h Associationciatian. Available at: httP;11
12. Gur S, Ron S. Does work with visual display units the Job Is Everyone's Business. Available at: www.aoa.oro/ ICTIA S m r 2009 m.
impair visual aclivities alter w o M Doc Ophthalmol. i G m.
u u ! pdl. Accessed December 28.2010.
1992;79:253-259. 33. American OptornetricAssociation. The Effects ol Com- 53. Federal State Statistics Service. Available at: www.oks.
13. Bhanderi DJ, Choudhary S, Doshi VG. A community- puter Use on Eye Health and Vision. Available at: ru/wos/oortal/0SI.Accessed December 28,2010.
based study of asthenopia in computer operators. Indian J ora/documanlsAnectsComouteruse.odf. Accessed August 54. ICT Statistics Newslog. Spain ends 2008 with a sub-
Ophthalmol. 2008;56:51-55. 31,2010. scriber base of 50.89 Mn. Available at: Hlww.itu.inVITU-01
14. lwakiri K, Mori I,Sotoyama M, el al. Suwey on visual
and musculoskeletalsymptoms in VOT workers. Sangyo
Eiseigaku Zasshi. 2004;46:201-212.
34. Kotegawa Y, Hara N, Ono K, el al. Influence of accom-
modative response and visual symptoms on visual
display terminal adult operators with asthenopia through
i I
55. IG Ultimo Segundo. Brasil ultrapassa marca de um
15. ljadunolaKT, ljadunolaMY, Onayade AA, Abiona TC. adequately corrected refracted errors. Nippon Ganka Gakkai celuiar por habitante. Available at:
Perceplionsof occupational hazards amongst office work- Zasshi. 2008;112:376-381.
ers at the Obafemi Awolowo University, Ile-lle. Niger J 35. Miyake-Kashima M, Dogru M. NojimaT, et al. The oor+habilanlelnlAccessed November
Med. 2003;12:134-139. effect of antirellectionfilm use on blink rate and asthenopic 18,2010.
16. Aakre BM, Doughty MJ. Are there differences behveen symptoms during visual display terminal work. Cornea. -.
56. Ministrvof lndustrv and Technoloav of the Peoole's
'visual symptoms' and specilic ocular symptoms associated 2005;24:567-570. Republic oi~hina. v i l a b l e www.miit.oov.cn/ '
~ at:
-
with video display terminal (VDT) use? Cont Lens Anterior 36. Lin CJ, Feng W, Chao CJ, d al. Effects of VDT work-
Eye. 2007;30:174-182. station lightingconditions on operator visual workload. Ind Mrnl. Accessed December 13.2010.
17. Vertinskv R. Forster B. Prevalenceof eve strain mono Health. 2008;46:105-111. 57. Prime-Tass. Available at: www.orime-lass.
radiologistsf influence of viewing variables on symploms: 37. Medical News Today. 3-D TV a Movies Look to
d
AIR. 2005;184:681-686. Attract Viewers but not Evelyone can 'See' What All the 19017865D79A%7D.uil. Accessed July 21,2010.
18. Richman JE, Laudon RC. A survey of the prevalence of Hype Is About. Medical News Today. M q 19.2010. Avail- 58. ProcontentRu AC&M Ukrainian Cellular Subscriber
binocular & accommodative dysfunctions in a sample of able at: Base April 2009. Available at: www.slldeshare.neVTosh-
optometry students. J Behav Optom. 2002;13:31-33. .- Accessed Sqkrbe~ 29,2010.
19. Gur S, Ron S, Heicklen-Klein A. Objective evaluation 34. Goodfellow G, Maino D. ASCDTECH: W n g edge
of visual fatigue in VDU workers. Occup Med (Lond). therapy for binocularvision ananalles. Op$m Ed. base-aaril-2M)9.Accessed April 2009.
1994;44:201-204. 2003;28:29. 59. Telecom Regulatory Authority of India. Available at:
20. U.S. Bureau of Labor Statistics. American Time Use 39. Convergence lnsuffidency TreQned T Shdy Group.
M
Survey Summary. June 22,2010. Available at: hllP;U Randomized clinical trnl of 8-eabmbb -
r -.Accessed
convergence insulficieneyin d t i b k h Ophltrdmd.
~ December 28,2010.
Accessed September 1,2010. 2008;126:1336-1149. 60. TMCnews. Research and markets adds report: Germany
21. U.S. Bureau of Labor Statistics. Computer and Internet 40. ConvergenceI n s u m T M TIM 91@ 1 -telecoms. IP networks and diaital media. Available
6 q.
m
Use at Work Summarv. Auaust 2.2005. Available at: h W 1 Lono-term effectivenessd br at: mm.tmcnet.comlusubmiV2W9M6n.
Accessed June 12,2009.
Accessed September 9,2010. 61. U.S. Census Bureau. Available at: www.census.oov/
22. U.S. Bureau of Labor Statistics. Computer Use by 41 Maino D. 8 p p l i i w Y d r W m , v. Accessed December 28,2010.
Home Workers. March 7,2002. ~vailable at: and perception. h UljBDJ, W m Q m O . @ k ) 62. Video Game Industry Stats. Available at: mm.arabstats.
Computer A p p l i i i n 4 b . L I . W B m b 1 1 , v. Accessed May
Accessed September 1,2010. 24.2010.
23. Saslow R. For a few, 3-0 effects are not so special: 63:Maino OM. The binocular vision dysfunction pandemic.
projectiontechnique uncoversvision problems, even modation defidanqbe-- JW Optom Vis Dev. 201041:6-13.
REVIEW OF OPTOMETRY JUNE 15, 201 1 36