Asthenopia: A Technology Induced Visual Impairment

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Vision systems evolve over generations based on the needs of the users and the environment. In humans, evolutionary pressures led to the development of the need for clear distance visual acuity and …

Vision systems evolve over generations based on the needs of the users and the environment. In humans, evolutionary pressures led to the development of the need for clear distance visual acuity and binocular three-dimensional (3D) stereoscopic vision. These visual skills enabled us to effectively respond to threats in the environment that were distant and constantly
changing, and improved our odds of being the hunter rather than the hunted. When Johannes
Gutenberg developed the process for modern book printing in the mid 15th century, he set in motion the shift in visual demands away from the importance of seeing clearly at distance and toward
a time intensive two-dimensional near-point task such as reading....read more...

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  • 1. Visual Evolution Asthenopia: A Technology Induced Visual Impairment As technology advances, eye strain and other symptoms of asthenopia are on the rise. By Dominick M. Maino, O.D., M.Ed., and Christopher Chase, Ph.D. ision systems evolve over V Figure 1. Symptomatology of Asthenopia generations based on the (modified from AOA Optometric Clinical Practice Guideline) needs of the users and the environment. In humans, Headaches (including migraines) evolutionary pressures led to the development of the need for clear Nausea distance visual acuity and binocu- lar three-dimensional (3D) stereo- General fatigue scopic vision. These visual skills Sleepiness enabled us to effectively respond to threats in the environment Diplopia that were distant and constantly changing, and improved our Photophobia odds of being the hunter rather than the hunted.1 When Johannes Blurred vision Gutenberg developed the process Eye strain for modern book printing in the mid 15th century, he set in mo- Eye soreness/pain behind or inside eye tion the shift in visual demands away from the importance of see- Burning/tearing of eyes ing clearly at distance and toward Dryness (although there are other causes of this, including prolonged computer use) a time intensive two-dimensional near-point task such as reading.2 Difficulty reading The emergence of mass- produced print materials, such Irritability as books and newspapers, has resulted in patients experienc- Poor concentration ing eye strain, and for some individuals, resulted in academic basis, with potentially serious advances in these devices result and work limitations.3,4 As tech- health implications.1 This problem in viewing screens of diminish- nology advanced and electronic will continue to grow in scope as ing size. For example, films that media became more dominant, patients spend increasing amounts were once projected onto a screen eye strain has progressed to a of time performing near-vision that spanned the width of a wall problem encountered on a daily tasks via digital media and as can now be viewed on a handheld 28 REVIEW OF OPTOMETRY JUNE 15, 2011BL 028_RO0611_F6-FILM2[1].indd 28 5/26/11 2:56 PM
  • 2. screen that is a mere 2” x 3.” The Figure 2. Etiology of Asthenopia (AOA Optometric Clinical Practice Guidline) technology-induced visual impair- ments we are witnessing today are Type of Specific Diagnostic Categorical Descriptions the result of our vision informa- Dysfunction Categories tion processing system attempting Accommodative Accommodative Occurs when amplitude of accommodation is lower to undo a millennia of evolution Insufficiency than expected for patient age and adjust to a relatively sudden Ill-Sustained Amplitude of accommodation is normal, but fatigue change in the demands placed Accommodation occurs with repeated accommodative stimulation upon our vision. Asthenopia, which includes eye Accommodative The accommodative system is slow in making a strain and several other symp- Infacility change or when there is considerable lag between toms (figure 1), often occurs in the accommodative stimulus and the response patients whose visual systems Vergence Paralysis of Accommodative system fails to respond to any are capable of performing near- Accommodation stimuli (very rare) vision tasks for limited durations Spasm of Results from overstimulation of the parasympathetic of time. It should be noted that Accommodation nervous system asthenopia does not occur as a Vergence •Convergence Insufficiency: consists of a receded consequence of any weakness Dysfunction near point of convergence, exophoria at near, within the ocular musculature sys- reduced positive fusional convergence, and defi- tem, but rather from the sustained ciencies in negative relative accommodation near point demands now placed •Divergence Excess: exophoria or exotropia at far upon a visual system primarily greater than the near deviation by at least 10 prism designed for distance tasks. This diopters is frequently caused by a lack of •Basic Exophoria: having a deviation of similar appropriate cortical output that magnitude at both distance and near is necessary for accurate accom- •Convergence Excess: having near deviation at modative and fusional vergence least 3 prism diopters more esophoric than the dis- system responses, and for the tance deviation demands of the task.1 As seen in •Divergence Insufficiency: tonic esophoria is high figure 2, there are a number of when measured at distance but less at near etiologies for asthenopia, but a •Basic Esophoria: High tonic esophoria at distance, recent study of 30 to 40 year-old a similar degree of esophoria at near, and a normal myopic subjects with asthenopia accommodative convergence/accommodation (N=253) found that the most fre- (AC/A) ratio quently encountered oculo-visual •Fusional Vergence Dysfunction: having normal problem was ill-sustained accom- phorias and AC/A ratios, but reduced fusional ver- modation (54%).1,5 These findings gence amplitudes corresponded with a 2001 study •Vertical Phorias: these may be either comitant and of 18 to 38 year-old subjects that idiopathic or noncomitant, due to muscle paresis or reported accommodative disorders other mechanical causes in 61% of subjects.6 How Prevalent Is underestimated; 2) Patients expe- formed while wearing spectacles Asthenopia? riencing these symptoms may not or contact lenses. Gauging the prevalence of this always schedule an examination Research by Sheedy and associ- disorder has proven difficult for or report them while being exam- ates shows two different afferent three reasons: 1) If only one or ined due to the perception that pathways for the symptoms of two symptoms of a wide-ranging no treatment options exist; and asthenopia. The symptoms can symptomatology are assessed, 3) Patients may perceive these be divided into associations with then the frequency and impact symptoms as an expected result either external or internal factors. of asthenopia are bound to be associated with the near task per- External symptom factors (burn- REVIEW OF OPTOMETRY JUNE 15, 2011 29BL 028_RO0611_F6-FILM2[1].indd 29 5/26/11 2:56 PM
  • 3. Visual Evolution ing, irritation, tearing and Figure 3: Percentage of Patients Experiencing Particular Asthenopic dryness) are related to dry Symptom (NSIGHT 2009) eye while internal symptom factors (ache, strain and 80 headache behind the eyes) 69 70 are related to accommoda- 58 60 tive or binocular vision stress.7 50 A study was conducted 40 that included 3,800 vision- 29 30 corrected (contact lenses 19 or spectacles) patients 20 from China, Japan, Korea, 10 France, Italy, the United Kingdom and the United 0 Eye Strain Tired Eyes Headache After Near Pain Inside the Eye States that allowed for the Work determination of the preva- lence, frequency and impact of asthenopia upon the indi- vidual.8 The next set of four figures show the findings from and pain in the eyes, occurred in the ages of 10 and 39, when the this study. Figure 3 shows the fewer respondents than the other amount of near work is great- percentage of patients experienc- symptoms listed, but high percent- est.1 Many individuals with ing symptoms. Figure 4 identifies ages of these respondents tended chronic problems have learned the symptoms by region. Figure to experience these symptoms at to live with their condition and 5 pinpoints the symptoms expe- least three times or more each may not voluntarily reveal their rienced three to seven times each week (headaches after near work symptoms. Young children (pre- week. And, figure 6 highlights the 42%; pain inside the eye 33%) school and early grades) may have negative impact of symptoms. (figure 5). Not surprisingly, a fewer near-vision demands; more Results show that patients fre- pain-related symptom had the importantly, many children no quently experienced asthenopic highest percentage of patients matter their age are often unable symptoms with as many as 58% who found their occurrence to to describe their symptoms. These experiencing eye strain and 69% be very bothersome (headaches children often do not report the tired eyes (figure 3). Many of the after near work, 44%), which was symptoms associated with asthe- symptoms that involved a pain- almost twice as high as the next nopia because they consider them ful sequelae, such as headache symptom.8 This 3,800-patient as being what is normally experi- after near work and pain inside survey shows that a large number enced by all.1 the eye, occurred less frequently of patients suffer from asthenopia Those whose occupations but still affected 29% and 19% and the associated symptoms are require considerable amounts of of patients, respectively (figure experienced repeatedly during the close work are at an especially 3). Patients from Asia demon- week and have a negative effect high risk. Studies have noted that strated the greatest propensity on the individual’s quality of life. computer operators are particu- for all symptoms of asthenopia larly susceptible to asthenopia (figure 4). These data suggest that Which Patients Are At because a high percentage of com- the symptoms of asthenopia are Greatest Risk? puter users with symptoms have prevalent and that practitioners All patients are at risk for binocular vision problems and should be proactively inquiring if developing asthenopia, but the ocular discomfort increases with their patients are experiencing any extent of that risk varies from the extent of computer use.9-12 8 of these symptoms. individual to individual. Most In a study of 419 computer Pain-related symptoms, such patients report symptoms of operators in India, 46% suffered as headaches after near work vergence dysfunction between from asthenopia during or after 30 REVIEW OF OPTOMETRY JUNE 15, 2011BL 028_RO0611_F6-FILM2[1].indd 30 5/26/11 2:56 PM
  • 4. working on a computer.13 In a Figure 4: Percentage of Patients Experiencing Particular study conducted in Japan, 72% Asthenopic Symptom by Region† (NSIGHT 2009) of office workers who work with computers indicated that they 90 suffered from eye strain and/or 80 pain.14 These results were similar 70 to another Japanese study, where 60 70% of computer users reported 50 various degrees of visual fatigue.15 40 A Norwegian study of soft con- 30 tact lens wearers and those who 20 10 had undergone successful LASIK 0 surgery also reported 70% of Eye Strain Tired Eyes Headache After Pain Inside the Eye patients experiencing some symp- Near Work toms of asthenopia, with 63% Asia EU USA complaining of headaches.16 Computer users are not the only professions that are at risk for developing asthenopia. A sur- vey of 380 radiologists found that tive and vergence function among work and while engaging in recre- 36% reported eye strain.17 Profes- computer office workers over a ational activities. Many individu- sions (e.g., lawyers, accountants) five-day work week, suggesting als may not realize the cumulative that involve other types of inten- that those with dysfunctional bin- effect that this can have on their sive near work, such as extensive ocular system may be particularly visual system and general sense reading of printed materials, also susceptible to symptoms due to of well-being. The workplace is a increase a person’s risk for devel- computer use.19 significant source of demanding oping asthenopia.1 Those who are near-point tasks, with many jobs not employed, including retirees, What Factors Are Leading to requiring the use of a computer should not be viewed automati- an Increase in Asthenopia? for up to eight hours per day.20 cally as being at lower risk, as The performance of near-vision In 2003, 56% of those employed they may be spending a substan- tasks occurs during school, at (77 million employees) used a tial amount of time on the Inter- net seeking employment, playing video games, or keeping up with Figure 5: Asthenopic Symptoms that Occur Every Day or Three to friends and family by using Face- Four Times Each Week in Patients* (NSIGHT 2009) book and other forms of digital social media. 70 63 Any individual with an undiag- 60 57 nosed binocular vision dysfunc- tion is at significant risk for these 50 technology-induced visual impair- 42 40 ments as well. Research shows 33 that up to 56% of those 18 to 30 38 years of age exhibit signs and 20 symptoms associated with a func- tional vision anomaly and more 10 than 40% of optometric doctoral 0 students may have a binocular Eye Strain Tired Eyes Headache After Pain Inside the Eye vision dysfunction.6,18 Gur, Ron Near Work and Heicklen-Klein found a sig- nificant reduction in accommoda- REVIEW OF OPTOMETRY JUNE 15, 2011 31BL 028_RO0611_F6-FILM2[1].indd 31 5/26/11 2:56 PM
  • 5. Visual Evolution computer at work. Some Figure 6: Percentage of Patients* Who Found Their Asthenopic occupations have a greater Symptoms to be Bothersome (NSIGHT 2009) proportion of computer users, with the rates for 100 managers (about 80%) and sales/office workers (67%) 80 being particularly high.21 Additionally, 77% of those 60 working from home were 40 computer users as well.22 Computer use is not the 20 only source of demanding near-vision tasks. Reading of 0 Eye Strain Tired Eyes Headache After Pain Inside the Eye work-related printed mate- Near Work rials can also significantly Slightly bothersome Very bothersome contribute to the stressors placed upon the vision sys- tem. An overabundance of work-related near-vision tasks is companies add 3D capabilities to of vision correction in the past not the only reason why astheno- their products, video game play- can experience discomfort while pia is increasing in our patients. ing is also becoming a significant watching 3D.27 In one study of The use of various electronic contributor to the amount of time young adults with normal binocu- media, including cell phones, elec- spent viewing images in 3D.25 It lar vision, almost half experienced tronic messaging and texting, the should be noted that the Nintendo significant visual fatigue and dis- Internet, standard high definition 3DS system is a handheld device, comfort while viewing 3D.28 The and 3D televisions, and 3D mov- forcing users to view 3D images American Optometric Associa- ies and video games, increases the on a very small visually demand- tion estimates that between three demands placed upon an already ing screen.25 and nine million (and possibly taxed vision system. Figure 7 lists Three-dimensional viewing more) Americans have problems useful statistics on the inroads contributes an additional level of appreciating the 3D experience.29 that these electronic media have burden to the overload of near- With an increase in these visually made into peoples’ daily lives. vision tasks that visual systems demanding tasks, not only will are already struggling to perform. the time spent performing vision- The Future Is Now: 3D Individuals who have poor con- intensive activities continue to With the success of the 3D film vergence, accommodation, and add stress to our work day and Avatar and the development of visual tracking abilities—all of recreational activities, it will also 3D television and video games, which are necessary for single, require greater effort on our part exposure to this form of entertain- clear and comfortable 3D view- to appreciate these many new and ment is expected to increase in the ing—may experience blurred quality of life-changing technolo- near future. In 2010, more than vision, diplopia, dizziness and gies. 20 3D feature films were released. headaches when exposed to this ESPN is already providing pro- type of media. Consequences of Asthenopia gramming in 3D (e.g., 18 World Only now are we beginning Asthenopia often includes Cup matches), and the Discovery to study those who experience health-related consequences such Network will launch its own symptoms while viewing 3D as headache, diplopia, pain in 3D channel in 2011.23 In 2010, content. Patients with this newly and around the eyes and overall DirecTV began offering its sub- coined “3D Vision Syndrome” feelings of fatigue (figure 1). A scribers three channels dedicated require further clinical interven- person’s quality of life can be to 3D.24 tion and research.26 Even patients reduced as the pain and discom- As Sony, Nintendo and other who haven’t required any kind fort associated with accomplish- 32 REVIEW OF OPTOMETRY JUNE 15, 2011BL 028_RO0611_F6-FILM2[1].indd 32 5/26/11 2:56 PM
  • 6. Figure 7. Statistics on Electronic Media Use Internet Approximately 80% of Americans have access to the Internet.45 Internet use is not the domain of only the young, as 40% of Americans over the age of 66 years use it.45 In the U.S., an aver- age of 17 hours per week is spent looking at the Internet, with 2.8 hours/week for light users and 42 hours/week for heavy users.45 Over the last 10 years, Internet use has grown by 444% globally, with the largest increases in Africa (2357%), Middle East (1825%), and Latin America/ Caribbean (1032%).46 Electronic messaging Over 1 billion texts and 247 billion e-mails are sent daily.47-48 Cell Phone Americans use their cell phones an average of 21 minutes/day. Thirty-five percent of 8-year- olds in the U.S. own a cell phone.49 Internet access via cell phone increases annually.45 The top five countries with the most cell phones are: China (824.3 million), India (687.7 mil- lion), U.S. (285.6 million), Russia (213.9 million) and Brazil (194.4 million). The top five coun- tries with the highest percentage of cell phones per capita are: Russia (147%), Germany (130%), United Kingdom (123%), Ukraine (118%) and Spain (111%).50-61 Smart phones are the next stage of development of cell phones. This newest-generation of phone is evolving into a handheld computer that can also make phone calls. The amount of programs (or apps) continues to grow, exponentially expanding the number of uses and resulting in increased time using them. There are tens of thousands of apps available for Android phones and more than 300,000 for the iPhone. Gaming In 2012, the number of households worldwide with next-generation game consoles is expect- ed to be 190 million, 80% of which will be connected to the Internet.62 ing particular activities can lead Practitioners need to be proactive point activities. If the practitioner to patients no longer performing in determining the full extent of is not comfortable testing for them. Hayes and associates found their patient’s near-vision activi- binocular disorders or in provid- a small but significant relationship ties. It is also important to ask ing optometric vision therapy, between ocular symptoms and appropriate questions regarding the patient should be referred global measures of quality of life any asthenopic symptoms typi- to an eye care practitioner who and a large association between cally associated with binocular is.63 Such practitioners have been eye and physical symptoms.30 vision dysfunction. Because the certified by the College of Optom- Symptoms associated with asthe- patient may not realize that etrists in Vision Development (an nopia not only negatively affect not everyone sees the same way international organization) and a person’s productivity and aca- they do and that what they are can be found by logging on to demic performance, but also our experiencing is not normal, only www.covd.org. ability to perform work-related a carefully taken case history All patients can be at risk for and recreational tasks in an effi- can discover the problems your developing asthenopia, so prac- cient and comfortable manner.1 patients may have in this area. titioners should educate them on Answers received from the patient what it is and how it may develop. Treatment of Asthenopia should then be reviewed together For those patients with a greater Treatments for asthenopia are so it is clear that you and the risk for asthenopia based on their available, but as with any health patient are using the same words visual demands, information problem, the first step is diagno- to define the same things.31,63 should be provided concerning sis. The simplest way to assess A comprehensive assessment of visual hygiene and various meth- the presense of asthenopia due the individual’s binocular vision ods for modifying their near view- to internal factors is to stress the system should be conducted for ing environment. Practitioners accommodative and vergence sys- patients experiencing adverse should advise their at-risk patients tems during your examination.1 reactions when performing near- to do the following:32-33 REVIEW OF OPTOMETRY JUNE 15, 2011 33BL 028_RO0611_F6-FILM2[1].indd 33 5/26/11 2:56 PM
  • 7. Visual Evolution • When performing computer Vision therapy helps the patient are dominant. This relatively work, schedule periodic breaks to develop efficient visual skills new vision demand will con- where they look away from the and vision information process- tinue to develop in magnitude as monitor (generally for every 20 ing. The therapeutic procedures the time spent performing near minutes of computer use have re-educate the brain so that the tasks increases and as the size them look away for 20 seconds). individual can achieve single, of electronic displays continue • Make sure there is proper clear, comfortable, binocular to decrease. The inclusion of 3D lighting for performing near-point vision that improves eye coordina- viewing technologies only further tasks. tion, focusing and eye movement, complicates the problem. • Use proper ergonomics at the which ultimately enhances the As a large proportion of workstation. 3D viewing experience.37-38 Stud- patients are candidates for devel- • Use a larger font for onscreen ies have shown that office-based oping asthenopia, practitioners text. treatment (in addition to home- need to determine their level of • Blink often. based activities) is efficacious and risk by asking appropriate ques- Practitioners can also advise long lasting.39-40 In these studies, tions about their occupations, the patient that specially designed vision therapy intervention not the activities they pursue in their near-point corrective lenses can only eliminated symptoms, but free time, and the amount of time help relieve the symptoms associ- also improved functional abili- they spend performing near-point ated with asthenopia. Strategies ties––both accommodation and tasks. Practitioners also need specific to computer operators vergence. These remarkable to educate their patients about should also be employed to reduce results lasted at least 12 months ways they can reduce their risk the incidence of asthenopia. In a post intervention. For patients of developing asthenopia, such as study by Kotegawa and associ- who cannot attend in-office by taking periodic breaks from ates, computer operators (20-29 weekly vision therapy appoint- watching a computer screen and years of age) who had originally ments, out-of-office therapy using paying attention to the ergonom- been undercorrected or overcor- computer programs to improve ics of their workstation. The use rected experienced a reduction in vision function are also effec- of corrective and therapeutic headache, eye strain and tired eyes tive.26,39,41 lenses will often help to relieve after receiving accurate refractive Non-presbyopic patients, who symptoms while implementing an correction.34 The use of antireflec- are otherwise healthy but have individually prescribed program tive film on monitors and the use accommodative insufficiency, of optometric vision therapy can of certain colors (e.g., blue and can benefit from using multifocal frequently completely eliminate white rather than green and red) spectacles to reduce the astheno- the asthenopia. have also been shown to reduce pia associated with this focusing Asthenopia is a frequently the incidence of asthenopia in dysfunction.42-43 Because some encountered visual impairment some computer users.35-36 adult contact lenses wearers that can seriously threaten a Asthenopia can be successfully exhibit decreased accommoda- patient’s quality of life. It inter- treated with vision therapy. The tive abilities, consider using either feres with the quality of our work, goals of vision therapy are to near reading prescriptions in our performance in school and ensure that the patient can visu- conjunction with the single vision our enjoyment at play. Astheno- ally function efficiently and com- contact lenses or multifocal con- pia is a prevalent condition that fortably in school, at work and/or tact lenses if asthenopia develops deserves our full attention so in athletic activities, as well as to for these patients.44 that, once diagnosed and treated, relieve any symptoms. For accom- patients can pursue their interests modative therapy, treatment Conclusions to the best of their abilities with- increases the amplitude, speed, The world where people needed out experiencing pain or discom- accuracy and ease of the focusing the ability to respond to stimuli fort. ■ response. At the end of therapy, that were distant, potentially the patient should be able to make dangerous and constantly chang- Disclosure: Editorial assistance rapid and accurate accommoda- ing has been replaced with one provided by BioScience Commu- tive responses without fatigue. where sustained near-point tasks nications. 34 REVIEW OF OPTOMETRY JUNE 15, 2011BL 028_RO0611_F6-FILM2[1].indd 34 5/26/11 2:56 PM
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