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Computer vision syndrome: A review

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Abstract

Computers and mobile computing devices are being used by increasingly larger number of people today. This has led to an increase in the number of patients complaining about ocular and nonocular symptoms related to computer use. Eye-strain, tired eyes, irritation, burning sensations, redness of eyes, dry eyes, blurred, and double vision reported by the visual display unit users was termed "Computer Vision Syndrome" (CVS). It is a repetitive strain disorder characterized by one or more of the following symptoms - eyestrain, eye fatigue, burning sensations, irritation, redness, blurred vision, and dry eyes when associated with operating a computer and looking at a computer monitor in a temporal association. CVS has a multifactorial causation. Several factors have been linked to symptoms. Many treatment modalities have been described. Treatment needs to be tailored to the individual patient. However, a large body of work is still required to uncover gaps in our understanding of the problem. A specially designed ocular examination for computer users and associated counseling about the current good practices in computer use would go a long way in preventing loss of productivity and morbidity from the condition.
Journal of Clinical Ophthalmology and Research - Jan-Apr 2014 - Volume 2 - Issue 1 61
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DOI:
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Department of Ophthalmology, Hindu Rao Hospital and NDMC Medical
College, Delhi, 1Department of Ophthalmology, Swami Dayanand
Hospital, Delhi, 2Department of Medicine, Deep Chand Bandhu Hospital,
Delhi, India
Address for correspondence: Dr. Jatinder Bali, 55-D, Third Floor,
DDA Flats, Kalidas Road, Gulabibagh, Delhi - 110 007, India.
E-mail: drjatinderbali@yahoo.com
Manuscript received: 09.09.2013; Revision accepted: 27.09.2013.
Computer use is becoming ubiquitous. The affordable prices,
increased productivity, and social changes have led to computers
and mobile computing devices being used by a large proportion
of population. However, it has also led to increased number of
patients complaining about ocular and nonocular symptoms.
The initial concern about use of visual display terminals (VDTs)
was centered around radiation, which included X-rays, optical,
radio frequency, very low frequency, and extremely low frequency
radiation.[1] No clear evidence of any negative effects on computer
users was found in most studies.[2] There were apprehensions of
adverse effects on pregnant women, which were found to be
incorrect by evidence.[3]
An increased number of symptoms related to rheumatology,
orthopedics, psychiatry, and ophthalmology emerged in
literature.[4-7] Somatic disorders, depression, and obsessions were
reported in increased frequency in computer users especially
when the operating time was more than 30 hours per week and
the duration of usage more than 10 years. Eye-strain, tired eyes,
irritation, burning sensations, redness of eyes, dry eyes, blurred,
and double vision were reported by the visual display unit
users and termed “Computer Vision Syndrome” (CVS).[8-11] These
symptoms appeared to increase as duration of VDT exposure
increased.[12] “The ocular complaints experienced by computer
users typically include eyestrain, eye fatigue, burning sensations,
irritation, redness, blurred vision, and dry eyes, among others.
The condition of a 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 to as CVS. It is a
repetitive strain disorder”[11] defined by the American Optometric
Association as the combination of eye and vision problems
associated with the use of computers [Table 1].[13]
Table 1: Four major catagories of symptoms in computer
vision syndrome
Symptom
category
Symptoms Possible causes
Asthenopic Eyestrain Binocular vision
Tired eyes Accommodation
Sore eyes
Ocular surface-
related
Dry eyes
Watery eyes
Irritated eyes
Contact lens problems
Visual Blurred vision Refractive error
Slowness of focus
change
Accommodation
Double vision Binocular vision
Presbyopia Presbyopic
correction
Extraocular Neck pain Computer screen
location
Back pain
Shoulder pain
Blehm et al. categorized the symptoms in four major categories:
Asthenopic, ocular surface-related, visual, and extraocular.[11]
The ocular factors leading to CVS have been grouped into two
major areas:
1. Inappropriate oculomotor responses and
2. Dry eye
When viewing near objects miosis, accommodation and
Commissioned Article
Computer vision syndrome: A review
Jatinder Bali, Naveen Neeraj1, Renu Thakur Bali2
Computers and mobile computing devices are being used by increasingly larger number of people today. This has led to
an increase in the number of patients complaining about ocular and nonocular symptoms related to computer use. Eye-
strain, tired eyes, irritation, burning sensations, redness of eyes, dry eyes, blurred, and double vision reported by the
visual display unit users was termed “Computer Vision Syndrome” (CVS). It is a repetitive strain disorder characterized
by one or more of the following symptoms – eyestrain, eye fatigue, burning sensations, irritation, redness, blurred
vision, and dry eyes when associated with operating a computer and looking at a computer monitor in a temporal
association. CVS has a multifactorial causation. Several factors have been linked to symptoms. Many treatment
modalities have been described. Treatment needs to be tailored to the individual patient. However, a large body of
work is still required to uncover gaps in our understanding of the problem. A specially designed ocular examination
for computer users and associated counseling about the current good practices in computer use would go a long way
in preventing loss of productivity and morbidity from the condition.
Key words: Computer vision syndrome, management, pathophysiology, treatment
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62 Journal of Clinical Ophthalmology and Research - Jan-Apr 2014 - Volume 2 - Issue 1
convergence take place. Prolonged work at computer terminals
has been associated with changes in both relative accommodation
and vergence.[14] subjects over-accommodated by an average of
–0.50 to –0.75 diopter (D) when stimuli were placed at 40 cm
and by –0.75 D to colored letters on a colored background in two
different studies.[15,16] A high prevalence of exophoria, convergence
insufficiency and low fusional convergence have been reported
among VDT workers. Near point of accommodation was measured
for VDT users and nonusers in the beginning of the day at the start
of the week. It was measured again at the end of the day 4 days
later. the accommodative amplitude was reported to be decreased
significantly for VDT users (by 0.69 D) than nonusers (0.18 D)
between the first examination and the second examination
4 days later.[17] Another longitudinal study reported that subjects
below 40 years of age who used VDTs lost more accommodative
amplitude than who did not.[18] It has been suggested that an
inaccurate accommodative response (AR) during working at the
computer terminal or a failure to relax the AR at completion of
the near task is at the heart of the asthenopia experienced by
the users. Blurred vision at near and difficulty to shift to distant
gaze is a common complaint in CVS and accommodative infacility
was the most common oculomotor anomaly reported.[19,20] These
changes are transient and workers return to baseline values by
the end of workday or week. Substantial losses have not been
reported in longitudinal studies when corrected for age changes.
The comparisons between near work and computer use have
shown that the differences between computer and hard-copy tasks
are not compelling. Wick and Morse using an infra-red optometer
to measure the AR in emmetropes reported an increased lag of
accommodation of 0.33D in VDT users compared with hard copy
users.[21] Penisten et al. using dynamic retinoscopy could not
demonstrate any significant differences in printed card, VDT, or
simulated computer display when the intraobserver variability
was taken into account.[22]
VDT use has been associated with a small and temporary
myopic shift of refraction. These shifts are so small that distant
visual acuity is not affected. VDT users experienced a myopic shift
of about 0.12 D after the work period compared with no change
of refractive error of typists in a cross-sectional study.[23] Transient
myopia was reported by Luberto et al. in 20% of VDT workers at
the end of their work shift.[24] Interestingly, all subjects exhibiting
myopic change complained of asthenopia, but only 32.5% of those
with asthenopia demonstrated the transient myopic shift. This
clearly shows that other factors are at work in the symptomatology.
Objective evidence is not available in the literature to suggest that
the transient myopia acquires permanence over time or prolonged
use when compared with other forms of near work. Standing
up, moving away, and looking away from the computer can help
reduce ocular symptoms and also neck, back, and shoulder pain.
Levy et al. proposed an hourly break while others suggested it to
be split inside of the hour up to three times. The idea remains that
a frequent work break is taken to avoid repetitive stress disorder.[25]
In a study on 291 professional computer users, Telles et al. reported
that yoga practice appeared to reduce visual discomfort, while the
group who had no yoga intervention (WL) showed an increase in
discomfort at the end of 60 days.[26]
Maintaining a single posture over an extended period of time
can cause muscular and ocular problems. Variation in posture
while sitting behind the computers can improve the symptoms
associated with CVS. Frequent breaks with computer use have
been shown to increase comfort and relax the accommodative
system.[27] Taking a smaller break for 5-10 min more frequently is
better than taking a longer break every 2 or 3 hours.[28] A 10-15 min
break from the computer is recommended for every continuous
1-2 hours of computer use[4,29] but is supported by limited evidence.
Wiggins et al. reported that there was a significant increase in
the symptoms during the computer task if there was a residual
astigmatism of up to 1D. This is a common practice while
prescribing soft contact lenses. The authors suggested that toric
lenses or spectacle overcorrection be used in these cases.[30] For
hyperopic error and high myopic error it is suggested that both be
corrected to produce a clear retinal image and reduce the retinal
blur to reduce the ocular stimulus for accommodation.
Bilton has proposed a term ‘1,2,10’ (One to Ten) to describe
the commonly used distances for the current electronic forms
of written communication. Mobile phones at a distance of one
foot (about 30 cm), two feet (about 60 cm) to two and a half feet
for desktop devices and laptops, and 10 feet (about 3 meters) for
the television screens.[31] This new wave of devices has smaller
text sizes on smaller screens necessitating a change in the usual
paradigms of prescriptions. Sheedy and Shaw Mc Minn suggest
that a reserve of three times the visual acuity be present for
comfortable near vision tasks. Translated into real terms the usual
N9 newspaper print (6/19.2 letter) would need a visual acuity of
at least 6/6.4 for comfortable, prolonged viewing.[32] The working
distances reported by workers showed that the mean distance for
the small screen devices (75% people preferring distances between
26 and 40 cm) was lower than for hard copy use.[33] This set of
users would need a near prescription for the reduced distances
when presenting with asthenopia.
Visual performance is affected by a number of display
parameters, such as character size, structure, and style; and by
image contrast and stability.[34] The images on VDTs and liquid
crystal display (LCD) screens are composed of tiny, bright spots
called pixels or horizontal lines called rasters. They collectively
form images. These images blur at the edges and lack sharp edges
that the printed word has. The effect is of a blurred image of hard
print, which is not seen blurred because of the speed at which it
is refreshed or rewritten on the screen by the beam of signals. The
larger the number of dots or lines displayed on a monitor to make
the picture, the sharper and clearer is the appearance of the image.
Blurred images are known to cause stimulation of accommodation.
In the case of VDT it is proposed that there is an understimulation
of accommodation resulting in a lag of accommodation behind
the image on the screen.[35] Ziefle studied search reaction times
and fixation durations at resolutions of 62 dots per inch (dpi)
and 89 dpi and found that both increased significantly when the
resolution was lower. Visual fatigue correlated positively with
search reaction times and fixation duration.[36] Conventional
reading differs from digital form in that the latter is dependent
on “Pixels”, which result from an electron beam striking the
phosphor-coated rear surface of the monitor screen. The pixel
is brightest in the center and its brightness decreases toward
the outer edges unlike the print form of the word, which has
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complete contrast sensitivity till the edge and fades to white next
to it. The eyes accommodate well to printed texts due to well-
defined edges. They have difficulty in sustaining focus on pixels
due to blurred margins. It relaxes to a point called resting point
of accommodation (RPA), which is normally 67 cm or behind the
screen. Then the eyes again try to focus on the pixels and a vicious
cycle starts, keeping the accommodation in a dynamic state. It
becomes more visually demanding and even small uncorrected
refractive errors become significant in computer users.
The refresh rate of a monitor refers to the number of times the
screen is painted to make an image every minute. It is measured in
Hz (times per second). Critical fusion frequency (CFF) is the refresh
rate at which humans can no longer distinguish the pulsating
beams of light as separate entities (30-50 Hz). At low refresh rates,
the characters on the screen may appear to flicker. This results
in subjective complaints of irritation, fatigue, and headache.
Berman et al. identified a synchronous electroretinogram (ERG)
response for a VDT stimulus operating at 76 Hz.[37] Other studies
also indicate that at higher refresh rates the image blur is reduced,
blink interval is decreased, and reading speed also increases.[35,38,39]
VideoElectronic Standards Association (VESA) had recommended
a minimum refresh rate of 75 Hz that minimizes flicker at all
brightness levels.[37] In today’s scenario, the upper end of refresh
rates on most high end light emitting diode (LED) LCD monitors
range from 125 to 250 Hz. Therefore this may be set to at least
80 Hz levels though on older cathode ray tube (CRT) cathode ray
tube monitors 60 Hz was a common frequency till not so long ago.
A positive correlation between associated phoria (AP) (prism
required to eliminate fixation disparity) and symptoms has been
reported by some studies in the past.[40,41] Watten et al. reported
significant decrease in positive and negative relative vergences
(vergence range) at near both at the beginning and end of an
8-hour workday. It implied that computer use decreased the
subjects’ ability to converge and diverge appropriately.[42]
However, Nyman et al. found no significant change in positive
or negative relative vergence at near, distance and near
heterophoria and near point of convergence (NPC) after 5 hours
of VDT work.[43] Yeow and Taylor found no difference between
VDT users and nonusers over 2 year period of the NPC, near
horizontal heterophoria and AP in the same office environment.
NPC declined with age in this study but no significant difference
was observed between the two groups.[18] Jaschinski reported that
near vision fatigue was associated with greater exophoria (or less
esophoria) fixation disparity as the target was brought closer to
the observer. It suggested that symptomatic subjects would tend
to prefer a longer viewing distance to minimize exophoric fixation
disparity.[44] In more recent studies, a slightly reduced vergence
response has been reported to increase subject comfort during
computer use. In a study on 20 subjects using laptop computers,
the AR to the computer screen was measured using a Grand Seiko
WAM 5500 optometer and the AP by prism to eliminate fixation
disparity, using a customized fixation disparity target (central lock)
that appeared on the computer screen. No significant changes
were reported in accommodation or vergence during the 30-min
test period. CVS symptoms were worse in subjects with zero
fixation disparity compared with subjects with exo AP thereby
implying that those who had exophoric fixation disparity at near
may be more comfortable than those with accurate vergence.[45]
Thus the minimum oculomotor response that places the image in
Panum’s fusional area may be more desirable than accurate ocular
alignment. This may have a bearing in the spectacle prescriptions
for computer users. However, larger studies are needed before this
can have direct clinical bearings on management.
Dry eye incidence of 10.1-21.5% among office workers have
been reported from different subgroups in Japan.[46] It is postulated
that dryness, burning, grittiness, or heaviness after an extended
session at the computer terminal may be attributed to ocular
surface problems. Users’ eyes sometimes even hyperlacrimate
in an attempt to restore the chemical balance and rewet the
eye.[11] Environmental factors like dry air-conditioned interiors,
draught from ventilation fans, static buildup, airborne paper, and
general office dust can have some bearing on the ocular surface
symptoms. The blink rate while working on the computer has
been reported to be significantly less than the normal. This leads
to poor tear film quality. Mean blink rate went down from 22 per
min in relaxed state to 10 per min when reading a book and 7
per min on the VDT in a study on 104 office workers.[47] However,
the tear film quality measured by tear breakup time, Schirmer I
and Jones tests was not significantly affected during computer
use.[48] Different blink patterns were describe d in symptomatic
patients but none of them has been proved in subsequent studies.
Blink rates have been found to decrease with reduced font size,
reduced contrast, increased cognitive demand of task, and spacing
between characters and lines.[6,49] Words with upper case and
lower case combinations are better tolerated than all upper-case
documents. It is recommended that spacing between characters
and lines should allow one-half character space between words
and one character space between lines. Dark characters against
a light background display screen are better accepted compared
to the opposite.[6] Application of elastoviscous drops has not
been associated with improvement of blink rates.[50] A study
of 112 noncontact lens using computer operators found that
68% men and 73% women reported symptoms of dry eye.[51] A
videokeratoscopy-based study has shown that the optical system
of the cornea is adversely affected by a compromised tear film.[52]
Ocular tiredness has been associated with ocular dryness in the
past.[53] Increased evaporation and decreased blinking during
computer use leads to ocular surface changes and thus was
believed to result in ocular tiredness.[47] The incidence of dry eye
has been reported to increase with age. The prevalence of dry eye
and is more common in women than in men.[54] Artificial tears may
be useful in this subgroup with dry eye conditions. Otherwise it
does nothing to reduce symptoms. Frequently, shifting gaze from
printed word to screen and vice versa is associated with eyestrain
and should be addressed.[55-57] Squinting was termed to imply
squeezing eyelids by Sheedy et al., and it was believed to reduce
the blink rate but recent studies have shown that symptoms were
less when squinting was used in laboratory conditions. Dry eye
has been reported to be a cause of eye strain and its associated
symptoms in a subset of patients.[32,58] Objective evidence is still
sketchy on the issue.
Incomplete blinks are common in computer use. A positive
correlation between the percentage of blinks considered incomplete
and the symptom score was found in recent studies.[55] Incomplete
blinking was associated with staining patterns in the inferior cornea
in some studies.[59] A higher incidence of incomplete blinks was
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found with computer use as compared with hard copy of the same
task.[56,60] However, incomplete blinks are not altogether despicable.
It was found that voluntary blinking affected the concentration
on the task at hand. The partial blinks do not interrupt the
concentration on the task at hand as much as the complete blinks.[59]
Systemic diseases and systemic medications also have a
bearing on dry eye. Sjorgen’s Syndrome, rheumatoid arthritis,
collagen vascular diseases, thyroid disease, allergy, and
autoimmune disorders can have an effect on the symptoms and
dry eye. Drugs like diuretics, antihistamines, antipsychotics,
antidepressants, oral steroids, increased alcohol consumption,
and antihypertensives are associated with dry eye.[61] The ocular
condition is affected by the systemic conditions, systemic diseases,
and systemic medications. Thus all factors need to be taken into
account in assessing the patient’s symptoms.
Meibomian gland dysfunction is associated with evaporative
dry eye. This increases the symptoms reported with computer
use. Poorly applied cosmetics have similar effect by blocking the
openings of the meibomian glands.[11]
Bright illumination from large windows, over-head fluorescent
tubes, table lamps, and office lighting implements can wash out
screen character images and cause annoyance by reflection and
glare. Similarly sharp contrast between the illuminated computer
screen and hard copy written text leads to asthenopia. Glare was
found to increase the amount of time required to read relatively
easy passages but decreased the amount of time to read relatively
difficult passages.[62] For long it has been postulated that use of
antiglare filters can help alleviate the symptoms as the ambient
light passes through the glare filter two times (in and out) but the
light emitted from the monitor passes through the filter only once.
Conflicting reports on the intervention have been found. Some
small studies reported a benefit but one large study in the past
consisting of 25,064 volunteers showed that filters by themselves
did not reduce the occurrence of asthenopia.[63] The difference in
these studies was in the duration of use of the system. Most of these
studies used small times of work exposure. There was a significant
difference when the intervention was first adopted but over time
there was an adaptation to the use of filters. However, given the
fact that avoiding reflection and glare decreases annoying images, it
appears worthwhile to advocate the use of antiglare or screen filters.
Screen filters improved overall functional indices in schoolchildren
with myopia after half an hour of computer usage.[64] The accuracy
of work remains unaffected by use of screen filters. Blink rate is not
affected by use of screen filters. However, a larger body of work is
required before we can be sure of the benefits accruing from use of
antiglare screens or the type of spectral filters to employ.
It has been proposed that certain patterns of striped lines could
give rise to symptoms of eyestrain and this could be ameliorated
by use of colored lenses and overlays. Feigin et al. reported that
spectral filters in spectacles were of use.[65] However, conflicting
evidence emerged from other studies.[66,67] The studies are not
comparable because they employed different methods and
filters. Objective evidence in support of antireflective coating on
spectacles is thus limited even though they are frequently used
by computer professionals and prescribed by optometrists.
Contact lenses also show the effects of adaptation. Studies
revealed that use of contact lenses was associated with a higher
blink rate. York et al. examined the effect of contact lenses on
different tasks of varying difficulty. The blink rates decreased
with increasing level of difficulty. The mean blink rate was
more in the contact lens using group.[68] This effect was not
found by Pointer who allowed a one month adaptation period.
In his study, the task difficulty was the main factor deciding
blink rate.[69] However, contact lens wearers reported dry eye
symptoms 12 times more frequently than emmetropes and five
times more than spectacle users.[70] Workers on contact lenses
are more likely to suffer a higher severity of ocular discomfort.
The cause was believed to be lack of lubrication. However,
objective evidence shows that other factors may be at work,
which require more subtle tests to differentiate them from the
symptom free group. A major problem associated with contact
lens use is that the current practice of not correcting up to
1 D of astigmatism results in significant increase in symptoms.
This recommendation needs revisiting in light of the increased
amount of screen time. In borderline dry eye states the use
of soft lenses aggravates the symptoms experienced. Hence
correct patient selection is imperative when prescribing contact
lenses in computer users. Dry eye symptoms are more common
in contact lens wearers than in the general population.[71] In
a survey of U.S. eye care practitioners 18-30% of soft contact
lens wearers experienced symptoms of dry eye. The ocular
symptoms associated with dry eye varied in severity, frequency,
and intensity.[72]
Use of occupational glasses or computer glasses has been
described by some practitioners.[73] Independent objective
evidence is still not available from large studies. The use of
specialized presbyopia glasses (bifocal) has been described in
the past wherein the upper segment contained lenses focused
at the intermediate distance of the computer screen. However,
limited objective evidence limits their use. In addition the use of
laptops and mobile computing devices has changed the way we
look at the screens now.
Elastoviscous lubricating eye drops and eye ointments have
been prescribed to computer users frequently to alleviate dry eye
or as a placebo. Initially some studies reported that use of such
drops reduced the symptoms of CVS but this fact was refuted by
other studies later, which stated that the users were dissatisfied
with the therapeutic effects. Guillon et al. in their study on 20
subjects reported that use of povidone 2% preservative-free
eyedrops was associated with an improvement in symptoms
during sustained computer use.[74] Several studies based on
objective parameters have shown that topical instillation of
elastoviscous drops does not increase the blink rate. Acosta
et al. have reported that blowing a hot air stream onto the face
in the middle of playing a computer game did not increase the
blink rate.[75] In contrast, Portello et al. reported that increased
blink rate induced by using a metronome which is any software
or device that produces regular, metrical ticks or beats or clicks
during computer use did not result in difference in posttask
symptoms in computer users.[76] Looking down while reading a
mobile computing device reduces the exposed corneal surface and
negates the effect of reduced blinking rate. In desktop computers
this is not the case. Thus an evaporative dry eye condition can
occur. It was postulated that polyvinyl alcohol (PVA), dextran,
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poly vinyl pyrollidine would be better in this subgroup rather
than carboxymethylcellulose. However, convincing objective
evidence is still awaited.[47]
Limiting the computer and screen time is postulated to have
a dramatic impact on symptoms of CVS. Other workers have
suggested the 20/20/20 rule. After working on a computer for 20
min the computer user should gaze into the distance in excess of
20 feet for at least 20 s. It is believed that this will improve the
work efficiency and prevent eye strain.[77,78] However, any break
from work is as good as this rule. In fact, moving around between
tasks reduces the musculoskeletal symptoms experienced.
However, objective evidence is still awaited. Children often do not
notice discomfort or other symptoms and hence their computer
use should be regulated.[77]
In the USA, National Institute of Occupational Safety and
Health (NIOSH) suggests that computer users should have a
detailed ocular examination at the beginning of taking up the
computing job and then repeat it annually.[79]
Suggestions about ergonomic positioning of the computer and
its chair include the following:[79-81]
Use the computer monitor in an ergonomic position - one arm
distance or 40 inches away with a downward gaze of 14° or more
appears to help relieve the symptoms of CVS.[79] This is achieved
by placing the monitor so that the top line of screen is at or below
eye level Figures 1 and 2.
Prefer to use a chair specially designed for computer use so
that it provides necessary support to the back, legs, buttocks,
and arms. It should help avoid awkward postures, contact
stress, and forceful exertions. A height adjustable lumbar
support can be appropriately placed to fit the lower back. The
outward curve of the backrest should fit into the small of the
back. The adjustment should allow the user to recline at least
15° from the vertical. The backrest should lock in place or be
tension adjustable to provide adequate resistance to lower back
movement. Use the keyboard in such a position that the arms
and wrist are in neutral position. Avoid screen reflections, glare
from window, or overhead lights.
According to Occupational Safety and Health Administration,
the preferred viewing distance is 20-40 inches and the letter size
may be increased for smaller monitors. In the older guidelines for
work with VDTs the safe distance from the computer screen was
between 45 and 70 cm. The monitor should be kept directly in front
of the user’s chair so that the head, neck and body face forward
when viewing the screen. It should not be farther than 35° to the
left or right. It is recommended that while working from printed
material, the monitor should be placed slightly to the side and the
printed material kept directly in front. The printed material and
monitor should be kept as close as possible to each other. Viewing
the computer screen from a distance (48.42 and 65.33 cm) causes
more accommodation and convergence among people working
with computers than those who do not work behind computer
screens.[82] Visual strain in computer users was reported to be more
at 50 cm than 100 cm with characters twice as large. Therefore a
longer distance is more favorable than the reverse.
Single-vision lenses with a focal length designed for computer
work are to be preferred over bifocals in symptomatic computer
users. Bifocal presbyopic glasses are designed for near work in the
lower segment of the glasses thereby forcing the users to view
the monitor by tilting the head backward to see an appropriately
placed monitor through the bottom portion of their lenses. This
stresses the neck muscles, improved lighting quality, screen
design, ergonomically designed keyboard and mouse, alternative
input methods like touch, speech, stylus, etc., may go a long way
in preventing the symptoms related to CVS and computer-related
injuries (CRIs).[57,83,84]
The monitor should not be tilted too much. Excessive tilting
may distort the letters and alter their form by affecting contrast.
The monitor should be perpendicular to line of sight.
Desks and computer equipment with hard, angled leading
edges impacting a user’s arm, or wrist should be avoided. The
contact stress can affect soft tissues, nerves and blood vessels
resulting in tingling and sore fingers. One way to overcome it
can be padding edges of the sharp edged furniture with pipe
insulation or other such material. Furniture with rounded desktop
edges should be preferred.[79-82]
Adjustable setups where different family members especially
children can modify the setup for themselves is preferable in
Figure 1: Incorrect monitor position Figure 2: Correct monitor position
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Bali, et al.: Computer vision syndrome
66 Journal of Clinical Ophthalmology and Research - Jan-Apr 2014 - Volume 2 - Issue 1
households having kids.
The lighting intensity should be half of normal room
illumination when computers are used. The brightness of the
monitor should be turned up to the levels of the surroundings.
Lighting requirements vary with tasks at hand. In general, lighting
levels between 200 and 700 lux (approximately 20-70 foot candles)
measured at the workstation are recommended. More than 500
lux will usually be needed only to read poor quality documents.
Glare and reflections on computer screens should be avoided.
An antiglare cover and use of flat screens has been advocated
by workers.[85]
Dust can affect clarity of screen and cause glare, so all
monitors or screens should be free of dust.[84] Avoid turning the
air conditioning too high or direct draughts to the face.
The spectacle prescription needs to be customized to the
individual for computer users taking into account the working
distance. Bifocals or progressives if not properly customized may
not be optimal for computer distances. The direction of gaze is
important when making decisions on spectacle prescription. In
desktops it is important to bear in mind that there is a straight
ahead gaze focused at intermediate range and the downgaze at
near working distance may have to be explained to the user. The
refocusing from screen to print and vice versa can be avoided by
document holders attached to the screen. But the prescription has
to be understood by the patient and the usage understood by the
prescriber. Laptops and mobile devices are used at closer distances
than the standard desktop. Hence the concept of working distance
is important. A study of 79 VDT users reported that computer
glasses reduced the symptoms over the 15-week period[83] but
larger studies are required.
The children have to be educated about how far they should sit
from the screens and for how long. They usually tend to adapt to
poorer working conditions and overlook somatic complaints.[86] A
large body of work is required to address gaps in our knowledge.
In the absence of large studies it is only reasonable to assume
that children should spend only as much time as is absolutely
necessary before the devices. This will address the epidemic of
childhood obesity also. At a later date, we may realize that our
fears were ill founded but till the time we have made technology
absolutely safe for the children we should progress with caution.
Conclusion
CVS is a repetitive stress disorder characterized by a symptom
complex of eye-strain, tired eyes, irritation, burning sensations,
redness of eyes, dry eyes, blurred, and double vision apart
from nonocular complaints like neck, shoulder, and back pain
experienced by computer users. Several factors have been linked
to these symptoms. Many treatment modalities have been
described in literature and still more in anecdotes. Objective
evidence favors a multifactorial causation. The treatment needs
to be tailored to the individual patient. However, a large body of
work is still required to uncover gaps in our understanding of the
problem. A specially designed ocular examination for computer
users and associated counseling about the current good practices
in computer use would go a long way in preventing loss of
productivity and morbidity from the condition. The computers of
today are like the automobiles at the beginning of the twentieth
century. A lot of work needs to be done to make them like the
comfortable and safe automobile rendering service on our roads
today. The current knowledge needs to be shared along with the
relevance and importance that it deserves. The ophthalmologists
need to approach the syndrome complex scientifically to educate
his patients to make best possible use of the digital systems, which
are here to stay in a big way.
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PURPOSE: The aim of study was to assess the prevalence of CVS symptoms concerned to eye & other health related problems in digital device users METHODS: A Cross-sectional study was conducted among medical & engineering graduates & IT professionals during march-june2020.After taking informed consent the data of the effects and prevalence of CVS among digital device users were collected using a structured questionnaire RESULTS: Amongst 417 participants, most common & disturbing symptoms of Eye were eye strain, fatigue, dry eye (39.5%,20.7%,11.3%), headache & blurring of vision (40.1%&15.9%), neck & back pain (41%&37.6%), were experienced after 2-4hrs (28.5%) of continuous use.7.2%were unaware of above side effects. CONCLUSION: We noted 92.8% users were having CVS symptoms & duration of digital device usage is directly proportional to the severity of symptoms. CVS oftenly goes unnoticed. People might not have the appropriate vocabulary to label & describe their symptoms, hence this study helps to seek early diagnosis and prevention.
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Dünya Sağlık Örgütü (DSÖ) tarafından 11 Mart 2020 tarihinde pandemi ilan edilen şiddetli akut solunum virüsü koronavirüs-2 (SARS�CoV-2) enfeksiyonunun (COVID-19 pandemisi) kontrol altına alınmasında aşılar umut oluşturmuştur. Bu kapsamda COVID-19 pandemisiyle mücadelede Türkiye’de inaktive SARS-CoV-2 aşısının (CoronaVac) uygulanmasına acil kullanım onayı verilerek sağlık çalışanlarıyla 14 Ocak 2021'de aşılama başlamıştır (Seyahi ve ark., 2021). Genel olarak aşı yanıtını etkileyen faktörler; aşıya bağlı etmenler, bireye ait etmenler ve sağlık sistemine ait etmenler olarak üç başlık altında sıralanmaktadır. Aşıya bağlı etmenler arasında aşının türü, aşının adjuvan içeriği, aşının uygulanma yolu, sayısı ve dozu olarak belirtilmektedir. Sağlık sistemine ait etmenlerde aşıların uluslararası standartlara uygun üretilmiş, uygun soğuk zincir koşulları sağlanmış, doğru şekilde sulandırılmış, kişi için gerekli şema ile doğru bölgeden, doğru dozda uygulanmış olması gerekliliği vurgulanmaktadır. Bireye ait etmenlerde ise yaş, eşlik eden hastalıklar, kullanılan ilaçlar ve beslenme durumu gibi değişkenler yer almaktadır (Velipaşaoğlu, 2020). Merkezi sinir sistemi ve immün sistem arasındaki karşılıklı etkileşimler, psikiyatrik bozukluklar da dahil olmak üzere hastalıkların ortaya çıkmasında ve vücudun dengesini korumada önemli rol oynarlar (Sadock ve ark., 2016). Nöroimmünofizyologlar, stresin, anksiyetenin ve depresyonun immün sistemin yalnızca koruyucu işlevini değil aynı zamanda düzenleyici işlevini de değiştirdiğini vurgulamışlardır (González-Díaz ve ark., 2017). Psikolojik, sosyal ve davranışsal faktörlerin, bağışıklık sisteminin aşı yanıtını önemli ölçüde etkileyebileceği belirtilmiştir (Madison ve ark., 2021). Literatürde SARS-CoV-2 enfeksiyonuna karşı geliştirilen aşılarla oluşan immün yanıt ile uyku arasındaki ilişkiyi araştıran, sonuçları yayınlanmış bir çalışma henüz bulunmamaktadır. Bununla birlikte mevsimsel influenza ve hepatit B aşılarına karşı gelişen immün yanıt ve uyku arasındaki ilişkiyi inceleyen önceki çalışmaların sonuçlarına dayanarak SARS-CoV-2 aşılarına karşı gelişen immün yanıtta uyku ve uyku kalitesinin rol oynayabileceği ileri sürülmüştür (Benedict & Cedernaes, 2021; Kow & Hasan, 2021; Lammer-van der Holst ve ark., 2021). Bu çalışmada, inaktive SARS-CoV-2 aşısı (CoronaVac) uygulanmış sağlık çalışanlarında ve tıp fakültesi öğrencilerinde oluşan kantitatif antikor seviyeleriyle uyku kalitesi, depresyon, anksiyete ve stres belirtileri arasındaki olası ilişkilerin değerlendirilmesi amaçlanmıştır.
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