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.

V ision 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 binocu- lar three-dimensional (3D) stereo- scopic 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 mo- tion the shift in visual demands away from the importance of see- ing 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 experienc- ing eye strain, and for some individuals, resulted in academic and work limitation^.^^^ As tech- nology advanced and electronic media became more dominant, eye strain has progressed to a problem encountered on a daily

98 REVIEW OF OPTOMETRY JUNE 15. 201 1

Y

~ m 1 . S ~ ~ l a f A s t h e n o p i a nodifid hom PdlA CipbnMe CIrnicid PM'W b~delim)

5?

4 Photophobia

@ Rwninghealng of- , . .

D i iu l ly reading

Poor concentration

basis, with potentially serious advances in these devices result health implications.' This problem in viewing screens of diminish- will continue to grow in scope as ing size. For example, films that patients spend increasing amounts were once projected onto a screen of time performing near-vision that spanned the width of a wall tasks via digital media and as a n now be viewed on a handheld

screen that is a mere 2" x 3." The technology-induced visual impair- ments we are witnessing today are the result of our vision informa- tion processing system attempting to undo a millennia of evolution and adjust to a relatively sudden change in the demands placed upon our vision.

Asthenopia, which includes eye strain and several other symp- toms (figure I ) , 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 sys- tem, 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 accom- modative and fusional vergence system responses, and for the demands of the task.' 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 fre- quently encountered oculo-visual problem was ill-sustained accom- modation (54%).'p5 These findings corresponded with a 2001 study of 18 to 38 year-old subjects that reported accommodative disorders in 61 % of s~b jec t s .~

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

I Figure 2. Etiology of Asthenopia (AOA Optornetr~c Ci~n~cal Pract~ce Guidl~ne) I Specific Diagnostic Categorical Descriptions

n..-5, ....,+:., 1 I .' I I - Accommod ,,., 7- Accommoc ,..., ,,,,.,....,..-...,...,,,,.,,,,......,,,..,...,.,.., Insufficiency than expected for patient age 3

<.x:zj Ill-Sustained Amplitude of accommodation is normal, but fatiguc Accommodation occurs with repeated accommodative stimulation

Accommodative The accommodative system is slow in making et Infacility change or when there is considerable lag between ,

'

the accommodative stimulus and the response Vergence Paralysis of Accommodative system fails to respond to any

Accommodation stimuli (very rare) 3 Spasm of Results from overstimulation of the parasympathet$Bd I Accommodation nervous system 1 @

4 Vergence *Convergence Insufficiency: consists of a receda Dysfunction near point of convergence, exophoria at near, .

. , .., , - ;i reduced positive fusional convergence, and defi- ciencies in negative relative accommodation *Divergence Excess: exophoria or exotropia at far greater than the near deviation by at least 10 prism diopters @Basic Exophoria: having a deviation of similar magnitude at both distance and near *Convergence Excess: having near deviation at least 3 prism diopbrs more esophoric than the dis, tance deviation *Divergence Insufficiency: tonic esophoria is high when measured at d i i c e but less at near *Basic Esophoria: High tonic esophoria at distance a similar degree of esophoria at near, and a norma

.< accommodative convergence/accommodation !4 (AC/A) ratio . -. s - '

.i ' *Fusional Vergence Dysfunction: having normal .a .n phorias and AC/A ratios, but reduced fusional ver-

gence amplitudes @Vertical Phorias: these may be either comitant and idiopathic or noncomitant, due to muscle paresis 9, other mechanical causes

--&-

underestimated; 2) Patients expe- riencing these symptoms may not always schedule an examination or report them while being exam- ined 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 per-

formed while wearing spectacles or contact lenses.

Research by Sheedy and associ- ates 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 (burn-

REVIEW OF OPTOMETRY JUNE 15, 201 1 29

ing, irritation, tearing and dryness) are related to dry eye while internal symptom factors (ache, strain and headache behind the eyes) are related to accommoda- tive or binocular vision stress.'

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 preva- lence, frequency and impact

Figure 3: Percentage of Patlents Expdgnclng Particular Asthenoplc Symptom (NSIGHT 2009) -

,_-..u'n . -- , Hea --..- . ... ~r Near Fain lnslae the E,- Work

"N = 3800 viaionconscted patients (Chine, Japen, Koree, Frence, Italy, UY USA).

of asthenopia upon the indi- ~ i d u a l . ~ The next set of four figures show the findings from this study. Figure 3 shows the percentage of patients experienc- ing symptoms. Figure 4 identifies the symptoms by region. Figure 5 pinpoints the symptoms expe- rienced three to seven times each week. And, figure 6 highlights the negative impact of symptoms.

Results show that patients fre- quently experienced asthenopic symptoms with as many as 58% experiencing eye strain and 69% tired eyes (figure 3) . Many of the symptoms that involved a pain- ful sequelae, such as headache after near work and pain inside the eye, occurred less frequently but still affected 29% and 19% of patients, respectively (figure 3). Patients from Asia demon- strated 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 are experiencing any of these symptom^.^

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 percent- ages of these respondents tended to experience these symptoms at least three times or more each week (headaches after near work 42%; pain inside the eye 33%) (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%), which was almost twice as high as the next ~ y m p t o m . ~ 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 for 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 great- est.' 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 asthe- nopia because they consider them as being what is normally experi- enced by all.'

Those whose occupations require considerable amounts of close work are at an especially high risk. Studies have noted that computer operators are particu- larly susceptible to asthenopia because a high percentage of com- puter users with symptoms have binocular vision problems and ocular discomfort increases with the extent of computer u ~ e . ~ - ' ~ In a study of 419 computer operators in India, 46% suffered from asthenopia during or after

30 REVIEW OF OPTOMETRY JUNE 15. 201 1

V i s u a l

computer at work. Some occupations have a greater Figure 6: Percentage of Patiants* Who Found Thelr Asthenopic

proportion of computer Symptoms to be BoUlersome (NSIGHTPWS)

users, with the rates for managers (about 80%) and 100 -

I

salesloffice workers (67%) 80 i being particularly high.21 Additionally, 77% of those ,*,,b 60 1 working from home were I computer users as

(%) 40 , I

Computer use is not the 20 1

only source of demanding I - near-vision tasks. Reading of work-related printed mate rials can also significantly contribute to the stressors

0 .I-.-

Eye Strain Tired Eyes Headache After Near Work

mSligMly bothersome -Very bothersome

Pain Inside the Eye

w = 3800 visiarrmncctad patianla (China, Japan, Koree, F m , Italy, UK USA). placed upon the vision sys tem.

An overabundance of work-related near-vision tasks is not the only reason why astheno- pia is increasing in our patients. The use of various electronic media, including cell phones, elec- tronic messaging and texting, the Internet, standard high definition and 3D televisions, and 3D mov- ies and video games, increases the demands placed upon an already taxed vision system. Figure 7 lists useful statistics on the inroads that these electronic media have made into peoples' daily lives.

The Future Is Now: 30 With the success of the 3D film

Avatar and the development of 3D television and video games, exposure to this form of entertain- ment is expected to increase in the near future. In 2010, more than 20 3D feature films were released. ESPN is already providing pro- gramming in 3D (e.g., 18 World Cup matches), and the Discovery Network will launch its own 3D channel in 2011.U In 2010, DirecTV began offering its sub- scribers three channels dedicated to 3D.24

As Sony, Nintendo and other

companies add 3D capabilities to their products, video game play- ing is also becoming a significant contributor to the amount of time spent viewing images in 3D.25 It should be noted that the Nintendo 3DS system is a handheld device, forcing users to view 3D images on a very small visually demand- ing screen.2s

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 con- vergence, accommodation, and visual tracking abilities-all of which are necessary for single, clear and comfortable 3D view- ing-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 interven- tion and research.26 Even patients who haven't required any kind

of vision correction in the past can experience discomfort while watching 3D." In one study of young adults with normal binocu- lar vision, almost half experienced significant visual fatigue and dis- comfort while viewing 3D.28 The American Optometric Associa- tion estimates that between three and nine million (and possibly more) Americans have problems appreciating the 3D exper i en~e .~~ 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 technolo- gies.

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 discom- fort associated with accomplish-

32 REVIEW OF OPTOMETRY JUNE 15, 201 1

j Internet

%ll Phone

Approximately 80% of Americans have accegs to the Internet" Internet use is not the domain of only the young, as 40% of Americans over the age of 66 years use it.' In the US., an aver- age of 17 hours per week is spent looking at the Internet, with 2.8 hourslweek for light users and 42 hourslweek for heavy users." Over the last 10 years, Internet use has grown by 444% globally, with the largest increases in Africa (2357%). Middle East (1825%), and Latin America1 Caribbean (1032%)."

Electronic messaging Over 1 billion texts and 247 billion e-mails are sent daily.474

Americans use their cell phones an average of 21 minuteslday. Thirty-five percent of &-r--. OMS in the U.S. own a cell phonema Internet access via cell phone Increases ann~a l l y .~ &j:,. 1

:1.-11 The top five countries with the most cell phones are: China (824.3 million), India (687.7 milt -.. 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%).5081

Smart phones are the next stage of development of cell phones. Thii 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 I Android phones and more than300,000 for the iPhone.

ing 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 asthe- nopia not only negatively affect a person's productivity and aca- demic performance, but also our ability to perform work-related and recreational tasks in an effi- cient and comfortable manner.'

Treatment of Asthenopia Treatments for asthenopia are

available, but as with any health problem, the first step is diagno- sis. The simplest way to assess the presense of asthenopia due to internal factors is to stress the accommodative and vergence sys- tems during your examination.'

Practitioners need to be proactive in determining the full extent of their patient's near-vision activi- ties. It is also important to ask appropriate questions regarding any asthenopic symptoms typi- cally associated with binocular vision dysfunction. Because the patient may not realize 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 thing^.^^,^^ 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 provid- ing optometric vision therapy, the patient should be referred to an eye care practitioner who is.63 Such practitioners have been certified by the College of Optom- etrists in Vision Development (an international organization) and can be found by logging on to www.covd.o~.

All patients can be at risk for developing asthenopia, so prac- titioners 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 meth- ods for modifying their near view- ing environment. Practitioners should advise their at-risk patients to do the f o l l o ~ i n g : ~ ~ - ~ ~

REVIEW OF OPTOMETRY JUNE 15. 201 1 a

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 associ- ated with asthenopia. Strategies specific to computer operators should also be employed to reduce the incidence of asthenopia. In a study by Kotegawa and associ- ates, computer operators (20-29 years of age) who had originally been undercorrected or overcor- rected experienced a reduction in headache, eye strain and tired eyes after receiving accurate refractive c ~ r r e c t i o n . ~ ~ The use of antireflec- tive film on monitors and the use of certain colors (e.g., blue and white rather than green and red) have also been shown to reduce the incidence of asthenopia in some computer

Asthenopia can be successfully treated with vision therapy. The goals of vision therapy are to ensure that the patient can visu- ally function efficiently and com- fortably in school, at work andlor in athletic activities, as well as to relieve any symptoms. For accom- modative 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 accommoda- tive responses without fatigue.

Vision therapy helps the patient to develop efficient visual skills and vision information process- ing. The therapeutic procedures re-educate the brain so that the individual can achieve single, clear, comfortable, binocular vision that improves eye coordina- tion, focusing and eye movement, which ultimately enhances the 3D viewing exper ien~e .~ ' -~~ Stud- ies have shown that office-based treatment (in addition to home- based activities) is efficacious and long la~ting.~~dO In these studies, vision therapy intervention not only eliminated symptoms, but also improved functional abili- ties-both accommodation and vergence. These remarkable results lasted at least 12 months post intervention. For patients who cannot attend in-office weekly vision therapy appoint- ments, out-of-office therapy using computer programs to improve vision function are also effec- tive.26,39.41

Non-presbyopic patients, who are otherwise healthy but have accommodative insufficiency, can benefit from using multifocal spectacles to reduce the astheno- pia associated with this focusing d y s f ~ n c t i o n . ~ ~ - ~ ~ Because some adult contact lenses wearers exhibit decreased accommoda- tive abilities, consider using either near reading prescriptions in conjunction with the single vision contact lenses or multifocal con- tact 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 chang- ing has been replaced with one where sustained near-point tasks

are dominant. This relatively new vision demand will con- tinue 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 devel- oping asthenopia, practitioners need to determine their level of risk by asking appropriate ques- tions 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 ergonom- ics 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 inter- feres with the quality of our work, our performance in school and our enjoyment at play. Astheno- pia 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 with- out experiencing pain or discom- fort.

Disclosure: Editorial assistance provided by BioScience Commu- nications.

94 REVIEW OF OPTOMETRY JUNE 15. 201 1

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