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| COMMISSIONED ARTICLE |
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| Year : 2014 | Volume
: 2
| Issue : 1 | Page : 61-68 |
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Computer vision syndrome: A review
Jatinder Bali1, Naveen Neeraj2, Renu Thakur Bali3
1 Department of Ophthalmology, Hindu Rao Hospital and NDMC Medical College, Delhi, India
2 Department of Ophthalmology, Swami Dayanand Hospital, Delhi, India
3 Department of Medicine, Deep Chand Bandhu Hospital, Delhi, India
| Date of Submission | 09-Sep-2013 |
| Date of Acceptance | 27-Sep-2013 |
| Date of Web Publication | 3-Dec-2013 |
Correspondence Address:
Jatinder Bali
55-D, Third Floor, DDA Flats, Kalidas Road, Gulabibagh, Delhi - 110 007
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2320-3897.122661
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. Keywords: Computer vision syndrome, management, pathophysiology, treatment
How to cite this article:
Bali J, Neeraj N, Bali RT. Computer vision syndrome: A review. J Clin Ophthalmol Res 2014;2:61-8 |
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],[5],[6],[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],[9],[10],[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]
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:
- Inappropriate oculomotor responses and
- Dry eye
When viewing near objects miosis, accommodation and 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 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 described 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],[56],[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 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 More Details 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, 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],[80],[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 [Figure 1] and [Figure 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],[80],[81],[82]
Adjustable setups where different family members especially children can modify the setup for themselves is preferable in 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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[Table 1]
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