about computer vision syndrome

1. Journal Club
(literature review)
Presenter
Suraj Chhetri
B.Optometry
Impact of computer technology on
health: Computer Vision Syndrome (CVS)

2. Objectives
• To provide the knowledge about computer vision syndrome and
factors associated with computer use
• To find out the prevalence of computer vision syndrome in
relation to occupations, age, gender in different literatures
• To identify the symptoms associated with CVS and how they are
inter-related to one another with the help of different
literatures

3. • To find out how CVS affects the quality of life in VDTs users
• To evaluate the potential therapeutic interventions for
patients with symptoms of CVS
Objectives

4. Introduction
• Today’s visual requirements may include viewing laptop and
table computers, electronic book readers, smartphones and
other electronic devices either in the workplace, at home or
in the case of portable equipment in any location
• Many individuals experience eye discomfort and vision
problems when viewing digital screens for extended periods
American optometry association

5. Introduction
• The use of computers and digital electronic devices for both
vocational and non vocational activities including e-mail,
internet access and entertainment is almost universal
• The viewing of digital electronic screens is no longer restricted
to desktop computers located in the work place
Computer Vision Syndrome: A Review; Clayton Blehm, et al : survey ophthalmology

6. Definition
• The ocular complaints experienced by computer users typically
include eyestrain, eye fatigue, burning sensation, irritation,
redness, blurred vision, and dry eyes etc..
• The condition of person experiencing one or more of these
ocular complaints as a result of operating a computer and
looking at a computer monitor is generally referred as
“computer vision syndrome”

7. • It is a repetitive strain disorder that appears to be growing
rapidly, with some studies estimating that 60 million
population affected by CVS
• Non-ocular symptoms include headaches, pain in the
shoulders, neck or back.

8. • It is defined by American association of optometry as “a complex
of eye and vision problems related to activities, which stress the
near vision and which are experienced in relation or during the
use of computer.”
• Computer Vision Syndrome, also referred to as “Digital Eye Strain”
American association of optometry : ‘Guideline to clinical aspect of computer vision syndrome’1995

9. • Prevalence of CVS ranges from 75% to 90% among computer
users1
• Nearly 60 million people suffer from CVS globally2
• A million new cases of CVS occur each year2
1.American Optometric Association. The effects of video display
terminal use one year health and vision,15 jun 2013
2. A study of computer-related upper limb discomfort and computer vision syndrome. J Hum
Ergol (Tokyo) 2007;36:45-50.

10. • Apart from the duration of usage, factors such as poor lighting,
glare, screen brightness, vision problems and improper workstation
setup also account for eye and visual problems associated with the
computer usage
• Sustained period of close screen work results in visual fatigue
symptoms such as sore eyes and increased glare sensitivity
• Transient visual aberration resulting in black and white objects
visualized with colored tinge, is also documented with long duration
usage of visual display terminals.
Annals of Medical and Health Sciences Research 2014 Shantakumari N et al

11. • Dry eyes and related symptoms are associated with reduced blink
rate and horizontal gaze causing wider opening of the palpebral
fissure that lead to increased evaporation through exposed area
• Prevalence of CVS among subjects with pre-existing eye disease
was significantly higher than those without pre-existing disease
• Prevalence of CVS significantly higher in contact lens user than in
others
Computer vision syndrome among computer office workers in a developing country: an
evaluation of prevalence and risk factors; Ranasinghe et al. BMC Res Notes (2016) 9:150

12. Symptomatology
• They are subdivided into three potential pathophysiological
causes
I. Ocular surface related symptoms
II. Accommodative mechanism or asthenopic symptoms
III. Extra-ocular symptoms

13. Symptom category Symptoms Diagnosis
Asthenopic Eyestrain Binocular vision
Tired eyes Accommodation
Sore eye
Headache
Ocular surface related Dry eye
Watery eye
Irritated eye
Visual Blurred vision Refractive error
Slowness of focus change Accommodation
Double vision Binocular vision
Extra ocular Neck pain Computer screen location
Back pain
Shoulder pain
Computer Vision Syndrome: A Review
Clayton Blehm et al (jun,2005)

14. Visual problems among video display terminal (VDT) users in Nepal ;Gauri Shankar
Shresthaa, Fathimath Nestha Mohamed, Dev Narayan Shah; journal optometry ,26 April
2011

15. 1. Asthenopic symptoms
• Prolonged VDT usage has shown to cause diminished power of
accommodation, removal of the near point of convergence and
deviation of phoria for near vision
• Weakness of these important visual functions could be the
cause of eye strain in computer users
• A high prevalence of exophoria, convergence insufficiency, and
low fusional convergence were found among computer users

16. Oculomotor response
• Viewing any form of near target requires appropriate
accommodative and vergence responses to provide clear
and single vision of the object of regard.
• While both of these oculomotor functions have been cited
as contributing to the symptoms associated with computer
use

17. CVS: Accommodation and vergence facility
• Blurred vision, either at near or when looking into the distance
after prolonged computer use is a symptom commonly
associated with CVS.
• This could result from an inaccurate accommodative response
during the computer task or a failure to relax the accommodative
response fully following the near-vision demands.
• Patients’ symptoms frequently relate to near-visual activities,
and inappropriate responses, whether under or over-
accommodation relative to the object of regard are a common
cause of asthenopia.

18. • Accommodative infacility (35.5 %) was the most common
abnormality diagnosed followed by fusional insufficiency (14.8
%) and lag of accommodation (13.6 %)
• Both the sexes were equally affected for all these
abnormalities
Visual problems among video display terminal (VDT) users in Nepal Gauri Shankar Shresthaa,
Fathimath Nestha Mohamed, Dev Narayan Shah;2011

19. VDT’S and transient myopia
• Accommodative effort during near work is thought to be a
causative factor in the development of myopia
• Near work with VDTs results in a small, temporary myopic shift
called transient myopia
• But it’s significance with respect to creating permanent myopic
change is unknown
Mutti D et al : Is computer use a risk factor for myopia J Am Optom Assoc 67:521-30, 1996

20. Summery of asthenopic symptoms
• Change in accommodation and vergence function have been
reported to occur after work period at a VDT and these
changes have been proposed as objective indicators of
subjective visual fatigue
• They are most likely transient with workers returning to
baseline value by the end of the workday on week
• VDT’ s are a major source of near work for many adults but
do not appear to result in losses of accommodation and
vergence function beyond the ordinary effects of age

21. 2. Ocular surface related symptoms
• Computer users often report complaints after an extended
period of time at terminal
Eye Dryness
 Burning Sensation
 Grittiness
 Heaviness

22. CVS and Dry Eye
• Dry eye may be the primary cause of ocular fatigue such as
experienced when using a VDT when the blink rate is decreased
and exposed ocular surface area is increased causing desiccation
of eye
• Factors contributing to drying of the ocular surface are :
Environmental factor
Reduce blink rate
Increased exposure
Sex
Systemic disease and medication
Contact lens user
Ocular condition
Cosmesis

23. a. Environmental factors
• Dry air ventilation fans, static build up, dusty environment,
photocopy toners etc.
Carter JB et al Musculo skeletal problems in VDT work: a review. Ergonomics 37:1623-48, 1994

24. b. Reduced Blink Rate
• Most individuals normally blink between 10-15 times per
minute
• Blink rate at the computer is significantly less than normal

25. • A reduced blink rate at the VDT contribute to a poor tear film
quality and temporary stresses the cornea, resulting in
symptoms of dry eye
• This reduction in blink rate may as great as 60% and be also be
one of the basic pathophysiologic mechanism for the high
incidence of MGDs in computer users with significant ocular
surface complaints
Patel S et al : Effect of visual display unit on blink rate and tear stability, Optom Vis Sci
68:888-92, 1991

26. • The reading of text paper is normally performed while
looking downwards.
• This result in the eyelid covering a substantial portion of the
front surface of the eye, thus minimizing the evaporation of
tears
• On the contrary, computer users usually view their reading
material in a horizontal gaze
• This results in wider palpebral fissure and an increased
surface area exposed to the effect of evaporation
c. Increased Exposure

27. d. Sex
The prevalence of dry eye is slightly greater in female
than males
Salibello C, Nilsen E: Is there a typical VDT patients? A demographic analysis. J
Am Optom Assoc 66:479-83, 1995
Shimmura S, Shimazaki J, et al : result of a population based questionnaire
on the symptoms and lifestyle associated with dry eye . Cornea 18:408-11,
1999

28. e. Systemic diseases and medications
• Dry eye is associated with some systemic diseases (e.g. sjogren
syndrome, rheumatoid arthritis and several auto immune
diseases)
• Treatment diuretics, antihistamines psychotropic and some
antihypertensive are associated with dry eye , and patient taking
such treatment are more prone to get CVS
Liesegang T Deutsch T et al : Basic and Clinical Science Course Section 8, External Disease and
Cornea San Francisco, CA , American Academy of Ophthalmology , 2002 pp.76-81

29. f. Contact lens use
• Office workers wearing contact lenses are more likely to
suffer due to CVS.
• Contact lens lubrication is highly dependent on lubrication of
the eye
Wiggins NP, Daum KM, Snyder CA : Effects of residual astigmatism in contact
lens wear on visual discomfort in VDT use. J Am Optom Assoc 63:177-81, 1992

30. g. Ocular conditions
Dysfunctions of the lid glands as in blepharitis affecting
Meibomian glands causes lack of adequate lipid layer in tears
that causes more evaporation
Liesegang T Deutsch T et al : Basic and Clinical Science Course Section 8, External Disease
and Cornea San Francisco, CA , American Academy of Ophthalmology , 2002 pp.76-81

31. h. Cosmetics
• Poorly applied cosmetics can block the opening of the oil-
secreting Meibomian gland
• This in turn contributes to a rapid evaporation of the water
component of the tear film and the resultant discomfort

32. 3. Visual symptoms
Refractive error and CVS
• Given the need to achieve and maintain clear and single
vision it is important that the retinal image be focused
appropriately.
• Thus, spherical hyperopia and high myopia should be
corrected to reduce the ocular stimulus to
accommodation and minimize blur

33. • Out of 30 existing spectacle wearers (39.4 %), significant
change in spherical equivalent was found in 2 subjects (2.6 %)
• Another 14 subjects had spherical equivalent refractive error
greater than ± 0.5 D
Visual problems among video display terminal (VDT) users in Nepal Gauri Shankar
Shresthaa, Fathimath Nestha Mohamed, Dev Narayan Shah;2011

34. • Average change in spherical equivalent refractive error was
—0.6 ± 0.2 D
• Nine subjects had bilateral and seven subjects had unilateral
changes in refractive error
• Refractive error was the only abnormality observed in one
subject
Visual problems among video display terminal (VDT) users in Nepal Gauri Shankar
Shresthaa, Fathimath Nestha Mohamed, Dev Narayan Shah;2011

35. • In two similar experiments, Wiggins and Daum and Wiggins et
al examined the effects of uncorrected astigmatism while
reading material from a computer screen.
• In both studies the authors observed that the presence of
0.50– 1.00 D of uncorrected astigmatism produced a significant
increase in symptoms.

36. • Out of 176(334) students wearing either spectacle or contact
lens, 72.2% (127/176) of them had ocular symptoms of CVS
• Students wearing corrective lens either spectacle or contact
lens (n = 176) showed a higher risk of developing headache and
blurred vision
• Students who were wearing contact lens were at higher risk of
developing headache, blurred vision and dry eye compared
with non-contact lens users
Computer Vision Syndrome and Associated Factors Among Medical and Engineering Students in
Chennai; Annals of Medical and Health Sciences Research | Mar-Apr 2014

37. • In the absence of neurological lesions or disease affecting
the eye muscles , diplopia in computer vision syndrome
more likely to be attribute from glaring on computer monitor
for extended period of time
• Prevalence of diplopia in computer vision syndrome is 12.9%
Akinbinu RT, Mashalla YJ (2013). Knowledge of Computer Vision Syndrome among computer
users in the workplace in Abuja, Nigeria. J. Physiol. Pathophysiol. 4(4):58-63.

38. 4. Musculo- Skeletal problems
• Hales at all (1998) reports that approximately 22% of
computer user have musculo-skeletal problems such as neck
pain , back pain. Shoulder problems.
• Such a problems can be made worse by poor workstation
design , bad poster and long period of setting

39. Visual effects due to computer screen display
Display Quality
• Imaged are produced mainly by pixels and raster. The
image formed by them lack sharp edges. Slightly blurred
characters create an under stimulation of accommodation
and causes lag of accommodation behind the screen
• Resolution of monitors are associated with visual fatigue
• High levels of contrast and brightness are known to
represent the most common causes of character blur
Jaschinski W, Bonacker M, Alshuth E: Accommodation, convergence, pupil diameter and
eye blinks at a CRT display flickering near fusion limit. Ergonomics 39:152–64, 1996

40. Display Quality
• The space between characters and line also affects picture
quality and should allow for at least one half character space
between words and one character space between lines
Costanza MA: Visual and ocular symptoms related to the use of video display terminals. J
Behav Optom , 1994
• It is also recommended that screen contain dark character
against the light background display screen rather than
opposite
Effects of polarity of screen and color of display]. Sangyo Igaku 28:420–7, 1986

41. lighting and glare
• Bad lighting conditions of the surrounding area of the
computer can adversely affect the eyes of the user.
• Bright illumination from surrounding (head fluorescents,
large windows, desk lamps) can wash out screen character
images.
It creates a glare and reflection.
 It causes annoyance and visual fatigue.
• It has been shown that surrounding luminance significantly
reduces accommodation amplitude
Using a screen filter positively influences the physical well-being of VDU operators. Cent
Eur J Public Health 6:249–53, 1998 39. Hulgren GV, Knave B: Discomfort

42. • Refresh rate is the number of times per minute the screens
repainted to produce an image (measured in Hz).
• If the rate is too slow characters will start to flicker. It causes
annoyance fatigue and headache.
Refresh rates

43. • The critical fusion frequency (CFF) is the refresh rate that human
eyes do not distinguish the pulsating beams flicker as separate
entities.
• It is 30-50 Hz.
• The Video Electronic Standards Association (VESA) has
recommended a minimum refresh rate of 75 Hz that minimizes
flicker at all brightness level
• Studies have shown that much higher refresh rates decreases
ocular symptoms and improves the reading rate too.
• Liquid crystal displays (LCD) have very high refresh rates
compared to cathode ray tube (CRT)

44. continue
• The LCD screens significantly provided the best performance
in all conditions.
• It is an important advance in screen technology, optimizing
work productivity and minimizing oculomotor effort and
eyestrain in electronic reading
(www.planar.com/reseller/pdfR/LCD_productivitwhite_paper.pdf).

45. Radiation
• Ionizing radiation is known to cause human cellular
changes and break down the chemical bonding and change
the neutral molecules
• But VDTs do not produce or emit alpha, beta or gamma rays
or hard x-radiation

46. • Small amounts of soft x-rays are produced. But it is also
contained by the monitors’ glass screen
• Studies have shown that there is no evidence to support
that VDT operators face hazards like skin cancers,
spontaneous abortions and ocular abnormalities due to
ionizing radiation
Costanza MA: Visual and ocular symptoms related to the use of video display terminals. J Behav
Optom 5:31–6, 1994

47. Hours of computer use and symptoms
• Students who were using computer for 4-6 h were at significantly
higher risk of developing redness, burning sensation and dry
eyes compared to those who use computer for less than 4 h
• Students who took a break after every 2 h of continuous use of
computer had a higher risk of developing blurred vision, dry eyes
and neck and shoulder pain as compared to those who took a
break every hour
Computer Vision Syndrome and Associated FactorsAmong Medical and Engineering
Students in Chennai; Annals of Medical and Health Sciences Research ,Mar-Apr 2014

48. Computer vision syndrome and children
• Children have more access to computers either at home or at
schools now.
• Parents also encourage children at very early years to use the
computers
• According to American Optometry Association the impact of
computer use on children's vision involves three factors

49. 1. Children have a limited degree of self awareness. They
perform a task on computer for hours and hours without
breaks. This prolonged activity causes CVS
2. Children are very adaptable. They assume that what they
see and how they see is normal, even if the vision is
problematic. Therefore parents need to monitor their
work
3. As children are smaller than adults , the computer work
station arranged does not suit for children

50. Pathogenesis of CVS in summery
Contrast of image on computer screen is not sharp
because edge of characters are not well defined, so
eye have difficulty in focusing
Eye drift to resting point of accommodation
Eye start regaining the focus and put strain on ciliary
muscle of eye
Fatigue and tired

51. Dry eye from reduce blink rate (<5, normal > or= 15)
Repeated head posture change and wrong poster
change to focus
Strain on neck muscle and cervical spine
Neck and back pain
American association of optometry

52. Treatment
• Without any doubt, the treatment of CVS requires a
multidirectional approach due to the variety of complaints
between users.
• When treating a patient, it is important to consider both
ocular therapy as well as adjustment of the user’s
workstation and habits in an ergo-ophthalmologic approach.

53. • Adjust lights to reduce glare on the computer screen
• The monitor should not face any opened window to avoid
glare on the screen
• Use glare filters to reduce the glare on the monitor
• Adequate illumination of room and do not work in the dark
Proper lighting in the room

54. continue
• After comparing natural light, filament lamps, luminescent
lamps, sodium lamps, and mercury-arc lamps. It was found
that sodium lamps were the most adequate for high
functional capacity of the visual analyzer.
Novik AI, Soldatova AM, Martirosova VG, et al: [Visual work capacity with different sources of
illumination]. Vrach Delo 8:97–9, 1991

55. VDT positioning
• Improper posture distortions often lead to pain in back ,
neck and shoulder
• Suggested that distance between user and computer 35 to
40 inches
• Middle line of screen 5 to 6 inches below that eye level
• Lowering the monitor allows the VDT user to gaze
downward, thus exposing less ocular surface to ambient air
and reducing tear film loss
A field evaluation of monitor placement effects in VDT users. Appl Ergon 32:313–25, 2001

57. Work Break
• working for more than four hours at the VDT had a
significant association with asthenopia.
• Frequent breaks are recommended to restore and relax the
accommodative system, thereby preventing eyestrain
• for every 20 minutes of computer viewing, look into the
distance about 20 feet for 20 seconds to allow your eyes a
chance to refocus , also known as 20/20/20 rule
American optometry association,2016

58. Lubricating drops
• One of the most simple and therapeutic modes of therapy
are lubricating eye drops intended to relieve the symptoms
of dry eyes due to decreased blink rates.
• Higher viscosity eye drops may be more beneficial than the
balanced salt solution
Effect of VDUs on the eyes: report of a 6-year epidemiological study. Optom Vis Sci 73:512–
28, 1996

59. • A study among Indian ophthalmologist , retorted that 97.8%
of practitioners agreed that main mode of treatment of CVS
is artificial tears1
1 Bali J, Navin N, Thakur BR (2007). Computer vision syndrome: a study of the knowledge,
attitudes and practices in Indian ophthalmologists. Indian J. Ophthalmol.
• Antireflection coating helps in reducing glare and worker on
VDT using spectral filter were more comfortable at work
than those not wearing such glasses2
• 2Feigin AA (2003). Role of spectral filters for refraction dynamics in computer users. Vestn.
Oftalmol.

60. Oral omega-3 fatty acid treatment
• There was significantly improvement in symptoms , schimers
test value , TBUT time in patient having 0ral omega-3 fatty
acid 300 mg twice a day compare with control group
• Cytological feature being presence of smaller cells of both
polygonal and round shape and increase in goblet cell count
Oral omega-3 fatty acids treatment in computer vision syndrome
related dry eye; Contact Lens & Anterior Eye 38 (2015) 206–210

61. Conclusion
• A significant change in both optometric testing methods and
the design of ophthalmic lenses (particularly for refractive
errors) will probably be required
• As modern society continues to move towards use of
electronic devices , it is likely that an increasing number of
patients will present for eye examination due to symptoms
associated with CVS.
• Practioners need to consider what are appropriate
examination procedures and treatment regimens for these
individuals

62. • Prescribing routines may need to be reconsidered
• Further research is required to determine the efficacy of dry
eye treatment in reducing symptoms of CVS

63. Thank you