computer vision syndrome
SCREEN FOR Computer Vision Syndrome
The ever-growing use of digital displays at work, school and home warrant vigilance in identifying and effectively treating this condition.
Jeffrey Anshel, O.D., F.A.A.O., Carlsbad, Calif.
Thanks to the prevalence of electronic displays (e.g. computers, laptops, tablets, e-readers, MP3 players, portable video game systems and smart phones), more patients than ever before are at risk for developing computer vision syndrome (CVS). (See “CVS: A Display,” page 39.) For this reason, it's imperative we make a point of conducting CVS-related patient questioning, perform CVS testing, should patient questioning reveal its possible presence, and know how to effectively treat it.
Here, I discuss these patient questions, tests, how you can best manage CVS and the practice rewards of doing so.
Murphy's Law states: “You can't tell how deep a puddle is until you step in it.” So must we “step into” our patients' daily visual world, and start looking for CVS-related issues. To do this, I recommend you include a CVS-identifying questionnaire along with your patient history form. (See “Computer Workplace Questionnaire,” page 40.)
The proper seating for computer work, courtesy of the AOA.
You may be thinking, “Is it really necessary to include the questionnaire with all patient history forms? I doubt every patient is at potential risk for CVS.” My answer: You're wrong.
Some statistics to keep in mind: An estimated 195 million people are using computers on a regular basis, and in the next five years it is expected that number will easily surpass 200 million, according to North American data from Columbiabased Miniwatts Marketing Group. In addition, the U.S. Bureau of Labor Statistics predicts that by 2030, a full 20% of the workforce will be age 65 or older. This combination of facts will dictate some changes in our approach to patients. Further, a recent study revealed adults are exposed to screens — TVs, cell phones, computers, etc. — for roughly eight-and-a-half hours on any given day, with computer use coming in second behind TV viewing.1 And, those age eight to 18 spend more than seven-and-ahalf hours a day using a smart phone, computer, television or other electronic device.2
I recommend you send this questionnaire to patients prior to their appointment, so they can take digital display-viewing measurements before presenting. If your practice is super busy, have your receptionist direct patients to your website to download the questionnaire themselves, and tell them to bring it filled out to their appointment.
If the questionnaire reveals the patient may have CVS, schedule him/her for CVS diagnostic testing. Any of the “checked” causes/symptoms of the condition on the questionnaire should prompt further investigation.
Functional vision testing is needed to determine digital display visual stress. You should give the following tests, and carefully evaluate their results to determine the CVS diagnosis:
► Refractive error. Even small refractive errors, such as +0.50D, can be troublesome when attending to a highly demanding visual task, such as the computer. This is especially true for hyperopia and astigmatism, due to the excessive accommodation needed to maintain a clear image.
► Eye health. Tear film integrity, in particular, is critical for digital display viewing. Because of the intensity of the viewing task, computer users tend to blink infrequently. Consider performing a full battery of dry eye tests if the patient has dry eye symptoms or you question their tear integrity.
► Oculomotor abilities. Employ a cover test to reveal possible gross oculomotor abnormalities, such as binocular imbalance. Such conditions have been shown to significantly reduce visual comfort and productivity on computers.
► Vergence ranges. The patient's working distance to his digital display must be approximately centered in the vergence range to assure visual comfort. Sheard's (for exo-deviations) and Percival's (for eso-deviations) criteria have been shown as very accurate in predicting visual comfort.3
|CVS: A Display|
|CVS consists of blurred vision, dry eyes, eyestrain, headaches, double vision, color distortion, light sensitivity and neck, shoulder and back pain due to prolonged computer use.4 These symptoms have been associated with poor digital display lighting, display glare, poor seating posture, improper viewing distances from one's face to the digital display and uncorrected vision problems, such as hyperopia, astigmatism and inadequate eye focusing. In addition, presbyopia, due to its accommodative issues, can contribute to CVS symptoms as well. Those at greatest risk for developing CVS are those who generally use a computer three or more continuous hours daily.|
CVS occurs because computer work challenges the visual system in the following ways4:
► The letters on a computer display are often not as precise or sharply defined as a printed letter.
► The level of contrast of the letters to the background on the display is decreased.
► A digital display often has glare and reflections, challenging one's view.
► The viewing distances and angles associated with using a computer require certain focusing and eye movement needs.
As a result of the aforementioned causes, computer users who already wear spectacles or contact lenses may find they are not helpful. For instance, the spectacle wearer may tilt his head at an odd angle because his lenses aren't designed for viewing a digital display. Or, he/she may bend toward the display to achieve clarity. These body positions can cause muscle spasms or neck, shoulder and back pain.4
For some computer users, CVS symptoms are temporary and abate once ceasing computer work. For others, however, these symptoms persist even after they've stopped computer work. If the symptoms aren't addressed, they can continue and may worsen upon further computer use.4
► Accommodative ranges (negative relative accommodation/positive relative accommodation). Although accommodative range tests have “normal” ranges for the routine pre-presbyopic patient, the norms may not readily apply to the digital display working distance for these patients. This is because such ranges can vary depending on viewing distance. Therefore, acquire these ranges at the patient's computer viewing distance, watching the balance between the two findings rather than the absolute number of the finding. However, a finding of less than ±1.50D should be considered abnormal.
► Amplitude/flexibility of accommodation. One of the most common complaints of computer users is blurred distance vision immediately after near work. Be sure to measure flexibility of accommodation in the pre-presbyopic patient to determine whether this is an issue. Using a ±1.50D lens combination binocularly, expect that 10 cycles per minute of “flip” plus-to-minus-to-plus is within the normal range.
► Dynamic retinoscopy. This is one of the most valuable tests we can provide. The reason: It allows us to objectively determine the eye's active accommodative state while in use. Also, the test conditions (e.g. darkened room, horizontal gaze, viewing distance, etc.) can closely approximate the computer environment. Use 20/60 size letters for this test, as they are close in size to digital display lettering in most cases. Consider this finding as a starting point for prescribing computer vision lenses.
► Pupil size. Because room lighting while using a computer should be dimmer than normal, a larger pupillary aperture will result. This can exaggerate distortions of the screen letters and decrease depth of focus to the point of distortion.
|Computer Workplace Questionnaire|
1. Number of hours per workday of computer viewing. _____________
2. How long have you worked at a computer-based job?___________
3. Type of work habits: (circle one)
a) Intermittent- periods of less than 1 hour
b) Intermittent- periods of more than 1 hour
c) Constant- informal breaks, as required
d) Constant- regular breaks
e) Constant- no breaks, other than meals
4. How often do you clean your display screen? _________________
|Lighting in the work area: (check all that apply)|
|Fluorescent overhead only|
|Incandescent overhead only|
|Fluorescent and incandescent overhead|
|Fluorescent overhead and incandescent direct|
|Window light In front? Behind? To the side?|
|Window light control: Curtains? Blinds? Vertical/Horizontal?|
|Desk Lamp/Task Light|
|Other (describe) ________________________________________|
|How would you rate the brightness of the room: Very bright /Medium/Dim?|
|What color are the letters on your screen? _____________________|
|What color is the background of your screen? __________________|
|Viewing distance from your eye to display screen: __________inches.|
|Can the monitor be tilted? Y N|
|Can the monitor be raised / lowered? Y N|
|Does the screen have a glare filter? Y N If so, is it glass/mesh?|
|Top of display screen (above, equal to, below) eye level?|
|If above or below, by how many inches? ______________________|
|Viewing distance from your eye to keyboard: ______________inches.|
|Viewing distance from your eye to hard copy materials:______ inches.|
|Reference material is (to the side, below) the screen? Y N|
|If to the side, is it next to the screen or keyboard? Y N|
|Is this height adjustable? Y N|
|Is the monitor supported on a (stand/desk/CPU)?|
|Is this adjustable? Y N|
|Is all of your hard copy material visible without significant movements? Y N|
|Do you experience any of the following symptoms during or after COMPUTER work:|
|Blurred Near Vision||Color Distortion|
|Blurred Distant Vision||Light Sensitivity|
|Do you wear glasses while working at the computer? Y N|
|If yes, are they (single vision, bifocal or progressive)? Y N|
|Do you wear contact lenses while working at the computer? Y N|
|If yes, are they (soft, gas permeable, or hard lenses)?|
For those CVS patients without an uncorrected refractive error or who have a large pupil, simply having them change the way they view their digital display and their reference materials is often the most effective treatment.
To prevent glare, recommend the patient position his digital display away from glare-producing areas, such as overhead lighting and/or windows.4 Also, suggest using blinds or drapes on glare-causing windows and to replace the light bulbs in desk lamps that contain lower wattage bulbs. The latter is to better “match” the brightness of the screen. If minimizing glare-causing light sources isn't possible, recommend the patient purchase a neutral density (dark glass) anti-glare screen.
If proper working distance is an issue, educate the patient that his display should be 15° to 20° below his eye level (roughly four or five inches), as measured from its center, and 24 or more inches from his eyes.4
We must become ergonomic, as well as visual, experts with regard to CVS. To correct poor posture, educate the patient that chairs should be comfortably padded and conform to one's body, and that he should adjust his chair height so his feet rest on the floor. If the patient's chair has arms, tell him to adjust them to provide arm support while typing.4 This will prevent shoulder pain. In addition, tell these patients to avoid resting their wrists on their keyboards when typing, as this will preclude carpal tunnel syndrome.4 Finally, instruct patients to place their reference materials above the keyboard, though below their digital display.4 If this isn't possible, suggest they purchase a document holder to place next to their device. The purpose: To prevent constant head movement from the digital display to access their reference materials. Studies have shown that subjects prefer eye movements to head movements when looking at near objects.5
In cases in which the aforementioned tips don't provide enough relief, these patients may benefit from computer use spectacles. These spectacles may include lens tints or coatings to ease digital display viewing.
For CVS patients who have binocular vision problems, such as accommodative inflexibility, convergence insufficiency and inadequate fusion reserves, those who require a refractive correction or those who aren't satisfied with their every-day spectacles or contact lenses, prescribe occupational progressive ophthalmic lenses. (See “Occupational Lens Companies,” below.) Keep in mind, however, that those who have focusing problems may also benefit from vision therapy to relieve their CVS symptoms. Finally, inform all CVS patients to follow the “20/20/20” rule: Every 20 minutes, take 20 seconds, and look 20 feet away.
|Occupational Lens Companies|
|• Augen Optics: www.augenoptics.com|
• Carl Zeiss Vision: www.vision.zeiss.com
• ComputerEyed Eyewear: www.computereyed.com
• Crizal USA: www.crizal.com
• Essilor USA: www.essilorusa.com
• Gunnar Optiks: www.gunnars.com
• PC Peekers: www.pcpeekers.com
• Hoya Free-Form Company: www.thehoyafreeformcompany.com
• PixelOptics: www.pixeloptics.com
• PFO Global: www.profitoptix.com
• Seiko Optical Products of America: www.seikoeyewear.com
• Signet Armorlite: www.signetarmorlite.com
• Superfocus: www.superfocus.com
• VS-Eyewear: www.vseyewear.com
Digital displays aren't going anywhere any time soon. As a result, it's time we alter our patient questioning, testing and prescribing habits to address CVS and provide relief to the many undiagnosed patients. Doing so will not only create patient loyalty and referrals, but an increase in one's practice revenue too. For instance, keep in mind that second pair occupational glasses cost between $200 to $300. OM
1. The New York Times. Media & Advertising. 8 Hours a Day Spent on Screens, Study Finds. Stetler B. www.ny times.com/2009/03/27/business/media/27 adco.html?_r=1. (Accessed 6/20/12')
2. The New York Times. Education. If Your Kids Are Awake, They're Probably Online. Lewin T. www.nytimes.com/2010/01/20/education/20wired.html. (Accessed 6/20/12.)
3. Borish, I. Analysis; In Clinical Refraction, 3rd ed. Chicago, IL: Professional Press; 1970:879-880
4. American Optometric Association. Computer Vision Syndrome. www.aoa.org/x5253.xml (Accessed 6/20/12')
5. Von Noorden, G., 1985, In: Binocular Vision and Ocular Motility, CV Mosby, St. Louis, p. 81-83.
|Dr. Anshel has written numerous articles and books regarding nutritional influences on vision and computer vision concerns. He is the founder of Corporate Vision Consulting and is president of the non-profit Ocular Nutrition Society. E-mail him at eye email@example.com, or send comments to firstname.lastname@example.org.|