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HomemieyecareAsthenopia: A Technology Induced Visual Impairment

Asthenopia: A Technology Induced Visual Impairment

As technology advances, eye strain and other symptoms of asthenopia are on the rise.

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.1 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.2

The emergence of mass-produced print materials, such as books and newspapers, has resulted in patients experiencing eye strain, and for some individuals, resulted in academic and work limitations.3,4 As technology has advanced and electronic media become more dominant, eye strain has progressed to a problem encountered on a daily basis, with potentially serious health implications.1This problem will continue to grow in scope as patients spend increasing amounts of time performing near-vision tasks via digital media and as advances in these devices result in viewing screens of diminishing size. For example, films that were once projected onto a screen that spanned the width of a wall can now be viewed on a handheld screen that is a mere 5cm x 7cm. The technology-induced visual impairments we are witnessing today are the result of our vision information processing system attempting to undo a millennia of evolution and adjust to a relatively sudden change in the demands placed upon our vision




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The technology-induced visual impairments we are witnessing today are the result of our vision information processing system attempting to undo a millennia of evolution…

Asthenopia, which includes eye strain and several other symptoms (figure 1), often occurs in patients whose visual systems are capable of performing near-vision tasks for limited durations of time. It should be noted that asthenopia does not occur as a consequence of any weakness within the ocular musculature system, but rather from the sustained near point demands now placed upon a visual system primarily designed for distance tasks. This is frequently caused by a lack of appropriate cortical output that is necessary for accurate accommodative and fusional vergence system responses, and for the demands of the task.1 As seen in figure 2, there are a number of etiologies for asthenopia, but a recent study of 30 to 40 year-old myopic subjects with asthenopia (N=253) found that the most frequently encountered oculo-visual problem was ill-sustained accommodation (54 per cent).1,5 These findings corresponded with a 2001 study of 18 to 38 year-old subjects that reported accommodative disorders in 61 per cent of subjects.6

How Prevalent Is Asthenopia?

Gauging the prevalence of this disorder has proven difficult for three reasons:

1) If only one or two symptoms of a wide-ranging symptomatology are assessed, then the frequency and
impact of asthenopia are bound to be underestimated;

2) Patients experiencing these symptoms may not always schedule an examination or report them while being examined due to the perception that no treatment options exist; and

3) Patients may perceive these symptoms as an expected result associated with the near task performed while wearing spectacles or contact lenses.

Research by Sheedy and associates shows two different afferent pathways for the symptoms of asthenopia. The symptoms can be divided into associations with either external or internal factors. External symptom factors (burning, irritation, tearing



and dryness) are related to dry eye while internal symptom factors (ache, strain and headache behind the eyes) are related to accommodative or binocular vision stress.7

A study was conducted that included 3,800 vision-corrected (contact lenses or spectacles) patients from China, Japan, Korea, France, Italy, the United Kingdom and the United States that allowed for the determination of the prevalence, frequency and impact of asthenopia upon the individual.8 The next set of four figures show the findings from this study. Figure 3 shows the percentage of patients experiencing symptoms. Figure 4 identifies the symptoms by region. Figure 5 pinpoints the symptoms experienced three to seven times each week. And, figure 6 highlights the negative impact of symptoms.

Results show that patients frequently experienced asthenopic symptoms with as many as 58 per cent experiencing eye strain and 69 per cent tired eyes (figure 3). Many of the symptoms that involved a painful sequelae, such as headache after near work and pain inside the eye, occurred less frequently but still affected 29 per cent and 19 per cent of patients, respectively (figure 3). Patients from Asia demonstrated the greatest propensity for all symptoms of asthenopia (figure 4). These data suggest that the symptoms of asthenopia are prevalent and that practitioners should be proactively inquiring if their patients areexperiencing any of these symptoms.

Pain-related symptoms, such as headaches after near work and pain in the eyes, occurred in fewer respondents than the other symptoms listed, but high percentages of these respondents tended to experience these symptoms at least three times or more each week (headaches after near work 42 per cent; pain inside the eye 33 per cent)(figure 5). Not surprisingly, a pain-related symptom had the highest percentage of patients who found their occurrence to be very bothersome (headaches after near work, 44 per cent), which was almost twice as high as the next symptom.8 This 3,800-patient survey shows that a large number of patients suffer from asthenopia and the associated symptoms are experienced repeatedly during the week and have a negative effect on the individual’s quality of life.

Which Patients Are At Greatest Risk?

All patients are at risk of developing asthenopia, but the extent of that risk varies from individual to individual. Most patients report symptoms of vergence dysfunction between the ages of 10 and 39, when the amount of near work is greatest.1 Many individuals with chronic problems have learned to live with their condition and may not voluntarily reveal their symptoms. Young children (pre-school and early grades) may have fewer near-vision demands; more importantly, many children no matter their age are often unable to describe their symptoms. These children often do not report the symptoms associated with asthenopia because they consider them as being what is normally experienced by all.1

Those whose occupations require considerable amounts of close work are at an especially high risk. Studies have noted that computer operators are particularly susceptible to asthenopia because a high percentage of computer users with symptoms have binocular vision problems and ocular discomfort increases with the extent of computer use.9-12

In a study of 419 computer operators in India, 46 per cent suffered from asthenopia during or after working on a computer.13 In a study conducted in Japan, 72 per cent of office workers who work with computers indicated that they suffered from eye strain and/or pain.14 These results were similar to another Japanese study, where 70 per cent of computer users reported various degrees of visual fatigue.15A Norwegian study of soft contact lens wearers and those who had u



ndergone successful LASIK surgery also reported 70 per cent of patients experiencing some symptoms of asthenopia, with 63 per cent complaining of headaches.16

Computer users are not the only professions that are at risk for developing asthenopia. A survey of 380 radiologists found that 36 per cent reported eye strain.17 Professions (for example, lawyers, accountants) that involve other types of intensive near work, such as extensive reading of printed materials, also increase a person’s risk for developing asthenopia.1 Those who are not employed, including retirees, should not be viewed automatically as being at lower risk, as they may spend a substantial amount of time on the Internet seeking employment, playing video games, or keeping up with friends and family by using Facebook and other forms of digital social media.

Any individual with an undiagnosed binocular vision dysfunction is at significant risk for these technology-induced visual impairments as well. Research shows that up to 56 per cent of those 18 to 38 years of age exhibit signs and symptoms associated with a functional vision anomaly and more than 40 per cent of optometric doctoral students may have a binocular vision dysfunction.6,18 Gur, Ron and Heicklen-Klein found a significant reduction in accommodative and vergence function among computer office workers over a five-day work week, suggesting that those with dysfunctional binocular system may be particularly susceptible to symptoms due to computer use.19

Factors Leading to Increased Asthenopia

The performance of near-vision tasks occurs during school, at work and while engaging in recreational activities. Many individuals may not realise the cumulative effect that this can have on their visual system and general sense of wellbeing. The workplace is a significant source of demanding near-point tasks, with many jobs requiring the use of a computer for up to eight hours per day.20 In 2003, 56 per cent of those employed (77 million employees) used a computer at work. Some occupations have a greater proportion of computer users, with the rates for managers (about 80 per cent) and sales/office workers (67 per cent) being particularly high.21 Additionally, 77 per cent of those working from home were computer users as well.22 Computer use is not the only source of demanding near-vision tasks. Reading work-related printed materials can also significantly contribute to the stressors placed upon the vision system.

An overabundance of work-related near-vision tasks is not the only reason why asthenopia is increasing in our patients. The use of various electronic media, including mobile phones, electronic messaging and texting, the Internet, standard high definition and 3D televisions, and 3D movies and video games, increases the demands placed upon an already taxed vision system.

The Future Is Now: 3D

With the success of the 3D films and the development of 3D television and video games, exposure to this form of entertainment is expected to increase in the near future. Last year, more than 20 3D feature films were released. ESPN is already providing programming in 3D, and the Discovery Network announced the launch its own 3D channel in 2011.23 In the US, DirecTV began offering its subscribers three channels dedicated to 3D in 2010.24

As Sony, Nintendo and other companies add 3D capabilities to their products, video game playing is also becoming a significant contributor to the amount of time spent viewing images in 3D. It should be noted that the Nintendo 3DS system is a handheld device, forcing users to view 3D images on a very small visually demanding screen.25

Three-dimensional viewing contributes an additional level of burden to the overload of near-vision tasks that visual systems are already struggling to perform. Individuals who have poor convergence, accommodation, and visual tracking abilities – all of which are necessary for single, clear and comfortable 3D viewing – may experience blurred vision, diplopia, dizziness and headaches when exposed to this type of media.

Only now are we beginning to study those who experience symptoms while viewing 3D content. Patients with this newly coined “3D Vision Syndrome” require further clinical intervention and research.26 Even patients who haven’t required any kind of vision correction in the past can experience discomfort while watching 3D.27 In one study of young adults with normal binocular vision, almost half experienced significant visual fatigue and discomfort while viewing 3D.28 The American Optometric Association estimates that between three and nine million (and possibly more) Americans have problems appreciating the 3D experience.29 With an increase in these visually demanding tasks, not only will the time spent performing vision-intensive activities continue to add stress to our work day and recreational activities, it will also require greater effort on our part to appreciate these many new and quality of life-changing technologies.

Consequences of Asthenopia

Asthenopia often includes health-related consequences such as headache, diplopia, pain in and around the eyes and overall feelings of fatigue (figure 1). A person’s quality of life can be reduced as the pain and discomfort associated with accomplishing particular activities can lead to patients no longer performing them. Hayes and associates found a small but significant relationship between ocular symptoms and global measures of quality of life and a large association between eye and physical symptoms.30 Symptoms associated with asthenopia not only negatively affect a person’s productivity and academic performance, but also our ability to perform work-related and recreational tasks in an efficient and comfortable manner.1

Treatment of Asthenopia

Treatments for asthenopia are available, but as with any health problem, the first step is diagnosis. The simplest way to assess the presence of asthenopia due to internal factors is to stress the accommodative and vergence systems during your examination.1 Practitioners need to be proactive in determining the full extent of their patient’s near-vision activities. It is also important to ask appropriate questions regarding any asthenopic symptoms typically associated with binocular vision dysfunction. Because the patient may not realise that not everyone sees the same way they do and that what they are experiencing is not normal, only a carefully taken case history can discover the problems your patients may have in this area. Answers received from the patient should then be reviewed together so it is clear that you and the patient are using the same words to define the same things.31,45 A comprehensive assessment of the individual’s binocular vision system should be conducted for patients experiencing adverse reactions when performing near-point activities. If the practitioner is not comfortable testing for binocular disorders or in providing optometric vision therapy, the patient should be referred to an eye care practitioner who is.45 Such practitioners have been certified by the College of Optometrists in Vision Development (an international organisation) and can be found by logging on to www.covd.org.

All patients can be at risk for developing asthenopia, so practitioners should educate them on what it is and how it may develop. For those patients with a greater risk for asthenopia based on their visual demands, information should be provided concerning visual hygiene and various methods for modifying their near viewing environment. Practitioners should advise their at-risk patients to do the following:32-33

  • When performing computer work, schedule periodic breaks where they look away from the monitor (generally for every 20 minutes of computer use have them look away for 20 seconds).
  • Make sure there is proper lighting for performing near-point tasks.
  • Use proper ergonomics at the workstation.
  • Use a larger font for onscreen text.
  • Blink often.

Practitioners can also advise the patient that specially designed near-point corrective lenses can help relieve the symptoms associated with asthenopia. Strategies specific to computer operators should also be employed to reduce the incidence of asthenopia. In a study by Kotegawa and associates, computer operators (20-29 years of age) who had originally been undercorrected or overcorrected experienced a reduction in headache, eye strain and tired eyes after receiving accurate refractive correction.34 The use of antireflective film on monitors and the use of certain colours (for example, blue and white rather than green and red) have also been shown to reduce the incidence of asthenopia in some computer users.35-36

Treatment with Vision Therapy

Asthenopia can be successfully treated with vision therapy. The goals of vision therapy are to ensure that the patient can visually function efficiently and comfortably in school, at work and/or in athletic activities, as well as to relieve any symptoms. For accommodative therapy, treatment increases the amplitude, speed, accuracy and ease of the focusing response. At the end of therapy, the patient should be able to make rapid and accurate accommodative responses without fatigue.

Vision therapy helps the patient to develop efficient visual skills and vision information processing. The therapeutic procedures re-educate the brain so that the individual can achieve single, clear, comfortable, binocular vision that improves eye coordination, focusing and eye movement, which ultimately enhances the 3D viewing experience.37-38 Studies have shown that office-based treatment (in addition to home-based activities) is efficacious and long lasting.39-40 In these studies, vision therapy intervention not only eliminated symptoms, but also improved functional abilities – both accommodation and vergence. These remarkable results lasted at least 12 months post intervention. For patients who cannot attend in-office weekly
vision therapy appointments, out-of-office therapy using computer programs to improve vision function are also effective.26,39,41

Non-presbyopic patients, who are otherwise healthy but have accommodative insufficiency, can benefit from using multifocal spectacles to reduce the asthenopia associated with this focusing dysfunction.42-43 Because some adult contact lens wearers exhibit decreased accommodative abilities, consider using either near reading prescriptions in conjunction with the single vision contact lenses or multifocal contact lenses if asthenopia develops for these patients.44

Conclusions

The world where people needed the ability to respond to stimuli that were distant, potentially dangerous
and constantly changing has been replaced with one where sustained near-point tasks are dominant. This relatively new vision demand will continue to develop in magnitude as the time spent performing near tasks increases and as the size of electronic displays continue to decrease. The inclusion of 3D viewing technologies only further complicates the problem.

As a large proportion of patients are candidates for developing asthenopia, practitioners need to determine their level of risk by asking appropriate questions about their occupations, the activities they pursue in their free time, and the amount of time they spend performing near-point tasks. Practitioners also need to educate their patients about ways they can reduce their risk of developing asthenopia, such as by taking periodic breaks from watching a computer screen and paying attention to the ergonomics of their workstation. The use of corrective and therapeutic lenses will often help to relieve symptoms while implementing an individually prescribed program of optometric vision therapy can frequently completely eliminate the asthenopia.

Asthenopia is a frequently encountered visual impairment that can seriously threaten a patient’s quality of life. It interferes with the quality of our work, our performance in school and our enjoyment at play. Asthenopia is a prevalent condition that deserves our full attention so that, once diagnosed and treated, patients can pursue their interests to the best of their abilities without experiencing pain or discomfort.

Dr. Dominick M. Maino, OD, MEd, FAAO, FCOVD-A is a Professor of Pediatrics/Binocular Vision at the Illinois Eye Institute/Illinois College of Optometry and is in private practice in Illinois. He serves as the editor of Optometry & Vision Development and has authored 200 books, chapters, and articles. Dr. Maino has given more than 100 presentations worldwide.

Dr. Christopher Chase, Ph.D. is a Professor of Optometry at Western University of Health Sciences College of Optometry in California. He has been studying reading and vision for more than 20 years. Currently, he is exploring accommodation dysfunction and i



ts impact on reading and eyestrain.

Disclosure:
Editorial assistance provided by BioScience Communications.

References:

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31. Maino D

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