To most of us, computers have become an irreplaceable necessity in our lives at work and at home. Working on the computer screen at such a short distance can result in eyestrain, blurred vision, redness, irritation of eyes, and posture-related musculoskeletal problems, which is called Computer vision syndrome or digital eye strain.
The American Association of Optometrists defines Computer Vision Syndrome is a complex of eye & vision problems related to the activities that stress the near vision and which are experienced in relation to or during the use of computers1 They include eyestrain, headache, blurry near vision, slowness in changing focus, light sensitivity, eye irritation. Improper ergonomic practices can lead to pain in the neck, shoulder, and back, carpal tunnel syndrome, etc.
In the current digital world, there has been a rapid shift from paper to computers, mobiles, e-readers & other Visual Display Terminals (VDTs). Our eyes have not got fully adapted to working in a new visual environment for prolonged hours. Computer screens do not have good contrast, the characters (pixels) are brightest in the center & diminish in intensity at the edges in comparison to the good contrast on printed papers. Hence, making it difficult for our eyes to maintain focus. Instead, our eyes tend to drift out to a point called ' Resting Point of Accommodation'(RPA). RPA is approximately 30 inches, but increases as we age. Prolonged working hours on computers at a distance closer than RPA causes eye strain. The ciliary muscle works 2.5 times harder to focus on a monitor 12 inches away than it does to focus at 30 inches2
The presence of glare & reflections on the screen are additional problems which may make viewing computer difficult. Bright lights, windows, and overhead fluorescent lights often contribute to glares & reflections. Light from these sources needs to be controlled with proper blinds, screen filters or change of the room arrangement to minimize visual fatigue. Different age groups may require different light intensity to work with, workers over 50 years of age tend to require twice the light levels of young adults to perform the same task3
Blue light has a wavelength of between approximately 380nm and 500nm; making it one of the shortest, highest-energy wavelengths. They flicker more easily than longer, weaker wavelengths. Flickering creates a glare that can reduce visual contrast and affect sharpness and clarity. Artificial sources of blue light include digital screens (TVs, computers, laptops, smartphones, and tablets), electronic devices, and fluorescent and LED lighting.
Theoretically, commerciallyavailable blue light-filtering spectacle lenses reduce phototoxicity by 10.6%–23.6%, without degrading visual performance, and have thus been suggested as a supplementary aid for protecting the eyes against the blue light hazard4
In 2016, it was estimated that UK adults typically spend 4 hours 45 min per day using digital media, with a similar pattern in the USA, where approximately two-thirds of adults aged 30–49 years spend five or more hours on digital devices5 In India, people on an average spend 3-4 hours per day on mobile phones, tablets, computers, laptops, watching T.V. & another 2.5 hours daily on social media.
Today's children have never known a world without multiple screens, including TVs, computers, tablets, and smart-phones. Prolonged screen time is seen in children & teenagers. A study published in JAMA Pediatrics states that approximately 98% of US children aged 0 to 8 years live in a home with an internet-connected device and, on average, spend over 2 hours a day on screens. (6) This amount exceeds the recommended pediatric guideline that children spend no more than 1 hour per day viewing high-quality programming7
The presentation of CVS is worse in children than adults due to their level of development. Increased screen time can impinge on children’s ability to develop optimally. It can delay the development of gross motor skills in toddlers, it can disrupt interpersonal and communication skills8
Various studies have also shown that in older children, sedentary behavior due to overuse of digital devices can lead to lower physical fitness, obesity, higher cardiometabolic risk9 It can impact mental health also, children with higher screen time are likely to have disturbed sleep, low self-esteem, display social phobia, and also more stress & anxiety10 Ocular signs and symptoms include increased sensitivity to light, accommodation anomalies, headaches & eye aches, etc.
Pathophysiology of Digital Eye Strain (DES)
The symptoms experienced in computer vision syndrome are caused by 3 types of mechanisms.12
- Ocular surface mechanism - cause dry eye due to reduction in blink rate and increased corneal exposure caused by horizontal gaze at the computer screen
- Accommodative mechanism - blurred near or distance vision after computer use and difficulty refocusing from one distance to another, double vision, and slowness of focus change. Correction of refractive error (notably astigmatism) and presbyopia is accepted as an important intervention in DES sufferers.
- Extraocular mechanism – cause musculoskeletal symptoms such as neck stiffness, pain, headache, backache, and shoulder pain. These symptoms are well associated with improper placement of the computer screen.
A) Ocular surface-related symptoms
Computer users often report complaints of eye dryness, burning, grittiness, or heaviness after an extended period of time at the terminal. Dry eye may be a primary cause of ocular fatigue, such as experienced when using a computer when the blink rate is decreased and the exposed ocular surface area is increased, causing desiccation of the eye. Various factors causing dryness are
- Environmental Factors - the office includes hazards such as dry air, ventilation fans, static buildup, airborne paper dust, laser, and photocopy toner, and building contaminants.
- Reduced Blink Rate and Increased Exposure - computer users usually view their reading material in a horizontal gaze. This results in a wider palpebral fissure and an increased surface area exposed to the effects of evaporation. The higher gaze angle when viewing a computer screen results in faster tear loss and a greater percentage of blinks that are incomplete. It has been suggested that incomplete blinks are not effective because the tear layer being replenished is ‘defective’ and not a full tear layer.
- Sex - the prevalence of dry eye is slightly greater in females than males.
- Age - tear production normally decreases with age. Although dry eye can occur at any age in both men and women, post-menopausal women represent the group of individuals most affected by dry eye.
- Systemic Diseases and Disease Syndromes - dry eye is associated with various systemic diseases. A general review of the patient’s entire medical history aids in establishing a complete diagnosis. In the case of Sjogren syndrome, dry mouth and dry eyes can assist in making the diagnosis. Several autoimmune diseases like rheumatoid arthritis (secondary Sjogren's), thyroid-related disorders, rosacea, and connective tissue disorders like Systemic Lupus Erythematosis also have an association with dry eye.
- Systemic Medications - the most prevalent medications include diuretics, anti-histamines, psychotropic, and anti-hypertensives.
- Contact Lens Use - the contact lens surface should skate along the eye and eyelid surfaces with minimal resistance. If the ocular surface is dry, the lenses dry and adhere to the upper eyelid during the blink. This “friction effect” from dry eye produces discomfort.
- Meibomian Gland Diseases - increased tear evaporation, hyperosmolarity, inflammation lead to tear film dysfunction and dry eye. The most common disorder, anterior blepharitis, is caused by bacteria or seborrhic blepharitis. Meibomitis, an inflammation of the posterior meibomian glands of eyelids, affecting secretion of the lipid layer of the tear film, & may cause ocular surface damage. The lack of an adequate lipid layer contributes to rapid evaporation of the water component of the tear film thus causing discomfort.
- Cosmetics - poorly applied cosmetics can block the openings of the oil-secreting meibomian glands. This in turn contributes to a rapid evaporation of the water component of the tear film and the resultant discomfort.
B) Asthenopic symptoms
Prolonged computer usage has been shown to cause diminished power of accommodation, removal of the near point of convergence, and deviation of phoria for near vision.
- Headache - throughout the computer task, there is a need to maintain clear & single vision of relatively small targets. Refractive errors especially small degree of astigmatism and hyperopia; improper workplace conditions - including glare, poor lighting, and improper workstation setup, can all contribute to headache & eyestrain. These types of headaches are mild to moderate in intensity, often occur on either or both sides of the head, are not aggravated by physical activity, develop during the early to mid-part of the day, last from 30 minutes to the rest of the day, and are relieved by rest or sleep.
- Eye Strain - it can be caused from such problems as focusing spasm, anisometropia, astigmatism, hyperopia, myopia, or excess light. Many people may consider the tiring of their eyes as the ‘eyestrain’ condition. This is most often caused by a condition known as convergence insufficiency and can be easily treated with convergence exercises of the ocular muscles.
- Light Sensitivity - discomfort glare is largely caused by large differences in brightness in the field of view. It is much more desirable to eliminate bright sources of light from the field of view and strive to obtain a relatively even distribution of light. People are at greater risk to experience discomfort glare when the source of glare is brighter and when it is closer to the point of attention.
- Blurred Vision - it has been found that small amounts of refractive error contribute to the visual discomfort of computer users. Considering the working environment, blurred images can also arise from a dirty screen, poor viewing angle, reflected glare or a poor quality or defective monitor. All of these factors should be considered when this symptom occurs. A condition known as ‘transient’ myopia has been shown to be more prevalent in a population of computer users. Research has found that 20% of computer workers had a nearsighted tendency toward the end of their work shift.
- Neck and Back Pain - nature has made our visual system so dominant that we alter our body posture to ease any deficiency in the way we see. These situations are very common in the office environment and cause excessive postural accommodations, which lead to the symptoms of neck and back discomfort. If the monitor is set to eye level, the user is presented with a choice: either assume a more erect head/neck posture than preferred or employ a gaze angle that is too high. There is no ‘perfect’ screen height but, in general, when sitting in your chair gazing straight ahead, you should be able to look OVER your monitor. Most monitor positions are too high and that is the leading cause of neck pain.
Prevention of Computer Vision Syndrome
There are some things you can do to prevent or correct these problems:
- Position the screen 4-9 inches below eye level so that you gaze downward and prevent neck strain. Adjust your chair accordingly.
- Locate the monitor right in front of you, 20-28 inches from the eyes.
- If you’re consulting a document, position it the same distance from you as the screen.
- Limit glare by positioning lamps so that light is not reflected in the screen and does not disturb your peripheral vision.
- Limit reflections further by shading the screen with a file folder or purchasing an anti-reflection screen.
- If screen is too dark or too light, eyestrain can develop due to constant adjustment to areas of high contrast
- Clean the computer screen frequently.
- Work in a large, legible font and reduce it later if necessary.
- Have your eyeglass prescription checked regularly. Measure the distance of the screen from your eye and the angle at which you view it, and take these measurements to the optometrist. You may need a special pair of glasses for computer work.
- Take hourly breaks.
- Perform convergence exercises regularly if you are a myope.
With a few simple changes, the environmental causes of CVS can be easily eliminated. Some solutions to these environmental causes include:
- Reducing glare and harsh reflections on the computer screen by modifying the lighting in the room, closing window shades, changing the contrast or brightness of the screen, or attaching a filter or hood to the monitor. Position your computer so that any windows are to the side of the monitor, rather in front or in back.
- Adjust window blinds so that the sunlight is away from your screen and your eyes.
- Turn off overhead lights that are too bright. If this turns out to be not bright enough, switch to a lower wattage bulb, or use a desk lamp.
- Move your desk lamp to a spot where it doesn’t reflect on the screen or shine in your eyes.
- Attach a glare-blocking hood to your monitor. Much as a jacket hood can reduce the amount of sunlight that reaches your eyes from the top and sides of your head, a monitor hood reduces the amount of light that can reach your screen.
- Attach a glare filter to your screen.
- The computer screen should be at or just beyond an arm’s length away (about 20 to 26 inches) to give eyes a comfortable focusing distance. The screen should also stand straight in front of the face instead of off to the side to ease eyestrain. The center of the monitor should be about four to eight inches lower than the eyes to allow the neck to relax and to lessen the exposed surface area of the eye, which will reduce dryness and itching.
- Placing reference materials as close to the screen as possible. This will lessen the need to constantly refocus the eyes as well as the need to swing the head back and forth between the materials and the monitor. Using a document holder beside the monitor will minimize head and eye movements and focusing changes, and will decrease muscle fatigue, headaches and eye strain.
- Improving posture by using adjustable equipment to reduce strain on the back, neck, shoulders and eyes. Adjust the height of the chair so the knees are bent at a 90-degree angle with the feet flat on the floor or footrest. Sit straight against a back rest with the forearms on armrests and the elbows bent at a 90-degree angle. The keyboard and mouse should be located lower than the elbow and within easy reach of the hands. The head should be tilted slightly down while looking at the center of the computer screen.
- Giving the eyes and body frequent breaks from computer work to reduce eye and muscle fatigue. Since prolonged computer use requires a person to sit in the same position for an extended period, taking time out to stand, stretch and look around will not only help muscles, but will also give the eyes a chance to relax. If the opportunity to get up for full breaks is not frequently available, then “mini” breaks will suffice by looking up from the computer into the distance, about every 20 minutes. Frequent blinking will keep eyes from drying out and feeling itchy.
- Finding and improving other problems that may be affecting the eyes, including drafty, dry or dusty air. Try to keep air vents or drafts from blowing into the face and drying out the eyes. Low humidity or fumes in a room can also dry eyes out faster than usual. Dust, too, can irritate eyes as well as accumulate on the computer monitor, which will decrease the sharpness of the screen and may cause eyestrain.
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.
- Sit so that your head & neck are upright & in line with your torso, not bent down or tilted back.
- Face your screen directly, avoid viewing with head turned or back twisted.
- Keep elbows comfortably close to the body.
- Use a chair that provides support to the lower back.
- Position top of computer screen slightly below eye level.
- Adjust the position of your display to prevent reflections from overhead or outdoor lighting.
- When working with print documents, use a document holder that positions them at the same height & distance as your screen.
- Adjust the height of the chair so that your upper arms are perpendicular to the floor, forearms & wrists form a 90-degree angle with arms, your thighs are parallel to the floor & your lower legs are perpendicular to the floor.
Taking a quick walk around the office provides stretching of strained and fatigued muscles, a change of scenery, and possible relaxation.
Long periods of work without breaks are thought to be detrimental to ocular symptoms. Frequent breaks are recommended to restore and relax the accommodative system, thereby preventing eyestrain. Computer users should follow the 20-20-20 rule. That is, after 20 minutes of computer use, one should look at a distant object that is 20 feet away for 20 seconds
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. Although the higher viscosity drops did not vary blink rates, they normalized the inter blink interval and relieved ocular discomfort more efficiently than balanced salt solutions following computer use. Unfortunately, these more viscous eye drops also cause a decrease in overall visual acuity.
Presbyopes have much to consider when deciding the right format of eyewear. Conventional bifocals are designed for viewing at 16 inches at an angle of 20 degrees or more below the primary gaze. Computer screens are usually 24 inches away and only slightly below the primary gaze. General-wear progressive lenses are better, providing clear vision at an intermediate distance. Occupational progressive lenses are now available which incorporate a large area in the top half of the lens for mid-distance viewing (i.e., computer screen) and bottom half of the lens for near distance (i.e., keyboard, desktop). Some lenses even contain a small area for distance viewing, usually at the top of the lens.
Color-contrast optic filters are known to improve the color discriminating capacity when exposed to video display terminals.
To reduce blue light-induced eyestrain, eyeglasses with filter & screen filters or coatings for blue-violet light can be used.
Focusing the computer screen reduces the blink rate by one third to half of normal, so, encourage blinking frequently to keep the ocular surface moist & prevent dryness & irritation.
Monitor display quality should be increased by using high-resolution LCD monitors.
To summarize, the patient suffering from CVS can present to an eye care specialist in a variety of ways. A careful history and examination should reveal a correlation between computer usage and ocular complaints. It appears that the best treatment includes a multi-directional approach including modifications in the ergonomics of the workstation, eyeglasses correction, lighting and environmental factors, and properly scheduled work breaks from the video screen.
OSHA (Occupational Safety and Health Administration) TIPS
- Sit so your head and neck are upright and in-line with your torso, not bent down or tilted back.
- Face your computer screen directly. Avoid viewing your screen with your head turned or your back twisted.
- Keep your elbows comfortably close to your body.
- Use a chair that provides support for your lower back and has a cushioned seat with a contoured front edge.
- Keep your mouse close to your keyboard so you don't have to reach for it.
- Position your computer display so the top of the screen is at or slightly below eye level. This will allow you to view the screen without bending your neck.
- Adjust the position of your display to prevent reflections of overhead and outdoor lighting appearing on your screen.
- Put your monitor close enough to your eyes so you can comfortably read text on the screen without leaning forward.
- When working with print documents, use a document holder that positions them at the same height and distance as your computer screen.
- Use a hands-free headset when talking on the phone while working at your computer.
Also, adjust the height of your chair and desk so that:
- Your upper arms are perpendicular to the floor, not stretched forward or angled backward,
- Your forearms, wrists, and hands form a 90-degree angle with your upper arms,
- Your thighs are parallel to the floor and your lower legs are perpendicular to the floor,
- Your wrists and palms are not resting on a sharp edge.
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