Many individuals who spend long periods of time at video display terminals report a combination of eye and vision issues.1–3 According to the American Optometric Association,4 computer vision syndrome is “the complex of eye and vision problems related to near work which are experienced during or related to computer use.” These symptoms are not exclusively connected to work-related tasks,5 but can affect individuals of all ages due to the widespread use of video display terminals in everyday life.6 It has been recently noted that the use of video games can improve the visual performance of adults with amblyopia (spatial resolution of vision, sharpening of amblyopic vision, and enhancement of the contrast sensitivity function).7,8 A growing number of children of increasingly younger ages have access to new media (eg, computers, tablets, and video games) for both educational and recreational purposes.9 Several studies on the development and neuroplasticity of a child's brain10,11 indicated that temporary alterations of visual functions could arise, primarily in children 10 years of age or younger (a period known as the critical or sensitive period of the visual system) who spend too much time playing video games, both with and without prolonged exposure to other types of electronic screens (eg, televisions, computers, tablets, and smartphones). However, many children seem to ignore issues arising from visual distress most likely due to the adaptability and plasticity of their visual system.12 Several studies have examined the effect of video display terminals on the adult visual system,13–17 whereas few studies have been performed on children.12,18,19 In fact, attention toward the adolescent population has mainly focused on weight20,21 and behavior.22,23
During the past 15 years, in their daily clinical work with children, the authors observed specific findings in younger children that had not been observed in previous generations. The authors hypothesized that the prolonged use of video games could potentially be harmful to the developing visual systems of children. The aim of the current study was to examine a possible relationship between certain visual issues in children and their exposure to video games and electronic screens.
Patients and Methods
This observational, cross-sectional study was performed in an outpatient unit accredited by the Italian Regional Health Service and run by Dr. Rechichi. All healthy children between 3 and 10 years of age who attended the eye clinic between the beginning of 2012 and the end of 2013, either for routine examination or due to visual symptoms, were recruited. Exclusion criteria were congenital or acquired syndromes (eg, delays in mental development or severe hyperactivity) and eye diseases that cause alterations of the ocular surface or reduced visual acuity (eg, uveitis or albinism).
The authors considered the ethical aspects of the study and followed the guidelines of the tenets of the Declaration of Helsinki. The study was approved by the institutional review board of the Department of Experimental Medical-Surgical Sciences of Messina University, Italy, and a signed informed consent form was obtained from the parents.
The sample comprised 320 children (159 boys, 161 girls; mean age: 6.9 ± 2 years) who were examined by only one pediatric ophthalmologist (CR) using the same instruments (Table 1). The lower age limit of 3 years was chosen because this is the typical period when children start playing video games and using other electronic screens24 and the upper age limit of 10 years was chosen because the visual system of children is highly dynamic during the critical period and up to this age.
All patients underwent both ophthalmological and orthoptic examinations, and physiological, pathological, and ophthalmological histories were obtained from the parents. The orthoptic evaluation included ocular motility, identification of the dominant eye using the Dolman method,25 cover test for distance and near vision using the Lang Fixation Cube (LANG-STEREOTEST AG, Küsnacht, Switzerland) as a target for near fixation, and the 4 prism diopter base-out test.26 Stereopsis was tested with Lang-Stereotests I and II (LANG-STEREOTEST AG).27
The Lang-Stereotest is an easy-to-use test that uses random dots28 and cylinder gratings for image separation and is designed for the screening of stereoscopic vision in children. Two versions of the test plates, which differ only according to the three-dimensional objects to be recognized, are available. The Lang-Stereotest I displays a cat (disparity of 1,200 seconds of arc), a star (600 seconds of arc), and a car (550 seconds of arc), whereas the Lang-Stereotest II displays an elephant (600 seconds of arc), a moon (200 seconds of arc), and a truck (400 seconds of arc). In addition, the Lang-Stereotest II contains a star (200 seconds of arc) that can be viewed with one eye only.
When viewed monocularly, these tests do not provide clues regarding form aside from the star in the Lang-Stereotest II, whereas each stereoscopic form can be recognized binocularly. In contrast to most random-dot tests requiring red–green or polarized glasses, the images of the two eyes in the Lang-Stereotests are separated by a system of fine parallel cylindrical stripes (ie, a lenticular screen). Beneath each cylinder, there are two fine layers of pictures, one seen by the right eye and the other by the left eye. This has two advantages in that no glasses are necessary and the eye movements of younger children can be easily observed.
During examination, the examiner sits opposite the child to observe the eye movements more easily. The test plate is shown exactly at right angles and a distance of approximately 40 cm (16 inches). The child is asked whether he or she can see anything on the plate and the searching movements of the eyes are observed. When a three-dimensional object has been detected, the child is asked to look for additional objects and describe them. The child may then also point at the figures and should be able to determine which of them stands out the most. The possible results for Lang-Stereotests I and II are positive (correct localization and naming of two of the three hidden objects), negative (no object can be detected), and doubtful (only one hidden object is localized and named correctly).
Assessment of refraction was performed using the KR8100P autorefractometer (Topcon Corporation, Tokyo, Japan) by taking at least five measurements for each eye before the evaluation of subjective monocular visual acuity with optotypes at a distance of 3 m in both non-cycloplegic and cycloplegic conditions. Cycloplegia was obtained by cyclopentolate drops (1%) administered twice at an interval of 10 minutes. Astigmatism was defined as any refractive error with a cylindrical component of ±0.50 diopters or more. Any non-accommodated eye requiring correction with a spherical component of +0.50 diopters or more to reach 10/10 was defined as hypermetropic. The study of ocular surface and anterior segment was performed with the SL-3E Slit Lamp (Topcon Corporation) and the examination of the fundus by direct (Miroflex H2; Heine USA, Ltd., Dover, NH) and indirect (Sigma 150; Heine USA, Ltd.) ophthalmoscopy.
After the ophthalmologic examination, a questionnaire was used to collect the following information from the parents: the child's estimated average time spent playing video games (less than 30 minutes and not every day or 30 minutes or more every day), estimated average daily time spent using other types of electronic screens (less than 3 hours per day or 3 hours or more per day), and any asthenopic symptoms (ie, burning, blurred vision, ocular dryness, tearing, eye strain, eye ache, transient diplopia, dizziness, headache, and eyelid tic).
Patients were then divided into two groups: children who played video games for 30 minutes or more every day (video game group) and children who played video games for less than 30 minutes per day and not every day (control group). Both groups were then divided into two subgroups: children who used other types of electronic screens for less than 3 hours daily (low electronic use subgroup) and children who used other types of electronic screens for 3 hours or more per day (high electronic use subgroup) (Table 1).
The data obtained were collected and stored in a computer database (Excel 2013; Microsoft Corporation, Redmond, WA).
The chi-square test was used for comparison and a P value of less than .05 was considered statistically significant. For statistical analysis, due to the low number of patients with phoria, patients affected by esophoria and exophoria were combined into a single group (heterophoria) because a functional imbalance of the eye muscles is typical for both phorias. For statistical analysis of stereopsis, the children with doubtful and negative results on the Lang-Stereotests were combined into a single group.
Recently, there has been a sharp increase in the number of children spending long periods of time using video games in addition to other types of electronic screens.9 The number of video games and the possibility of using them on laptops, large television screens, or smaller devices such as tablets or pocket-size smartphones has never been as great as it is today and these games have become accessible to almost every child in modern societies.
Despite its observational character, the current cross-sectional study suggests that prolonged use of video games for 30 minutes or more almost every day in children up to 10 years of age might affect and compromise the development of their visual pathways. Could this complexity of symptoms be defined as a video game vision syndrome, similar to computer vision syndrome in adults, yet with some different features? Could the appearance of the highlighted symptoms in children playing video games be explained as the consequence of an excessive effort and a particular, fast, detailed performance of the still plastic visual system? Could the task of video gaming cause symptoms of both asthenopia and temporary cortical suppression of the non-dominant eye by mainly eliciting the monocular pathways of the dominant eye? The following observations might answer these questions.
First, symptoms of asthenopia were common, mainly in the video game group. Among all reported symptoms, the most frequent was headaches, although with different characteristics from headaches reported in computer vision syndrome. Whereas adults reported headaches at work, most children in this study did not complain of headaches while playing video games. Conversely, the patterns of headaches reported from children ranged from sudden attacks with sharp and acute pain that caused emergency situations for parents and pediatricians (including magnetic resonance imaging scans) to more continuous and persistent forms of headaches that led to a decrease in the child's liveliness and a character change. In fact, some young patients gave the impression of being indifferent, without energy, and almost apathetic, whereas a state of over-excitement and restlessness similar to attention-deficit or hyperactivity syndromes was observed in others. These children frequently suffered from insomnia, especially when they played video games to “relax” before going to sleep. In the video game group, the anamnesis might have been confusing and made it difficult to link the headache to visual fatigue because headaches may appear when no visual effort is being made or even during sleep. Other authors have argued that children often show greater adaptability than adults, such as when regarding viewing comforts. Hence, their high concentration on the game renders them less sensitive to uncomfortable glare, erroneous positioning of the device, and associated bodily symptoms than during less-focused activities such as school or homework.12
Second, 5.3% of children presented nervous tics. Because video game performance involves both the visual occipital and motor frontal cortex in a remarkably high-speed and repetitive way, these tics might be assumed to be direct consequences of a high level of brain stimulation. For example, the impulses to the brain increase rapidly in many games depending on the performance of the player and the level of the game, thereby leading to an elevated visual strain, particularly on the dominant eye, and resulting in a loss of fusion. This high level of brain stimulation could lead to a temporary loss of the orthotropic status and transient diplopia in young video game players, although frequent blinking would reset the system to orthotropia and single vision.30
Third, on the Lang-Stereotest I, a highly prevalent loss of stereopsis in the video game group was observed, whereas exposure to electronic screens other than video games had no influence on stereopsis in both groups. Common visual tasks at video display terminals (eg, writing or internet surfing) typically provoke saccadic movements of both eyes, whereas video games, which require a quick response to speedy images, might elicit mainly the faster monocular pathways, primarily limited to the dominant eye. Under high-speed gaming conditions, binocular vision would be unnecessary or even counterproductive and would slow the total visual performance. According to several studies, the visual system of children is still at the developing, critical stage, and structural changes have been observed according to the required performance and/or environmental stimuli.31 Therefore, the brain of a video game player might adapt to the required task by increasing the representation of the dominant eye at the expense of the non-dominant eye. However, these players most likely have healthy binocular cells in areas 17 and 18 of the brain, which are not stimulated due to the monocular pathways that are served first.
The greater brain representation of the preferred eye combined with the suppression of impulses from the non-dominant eye10,32 might determine an imbalance between the ocular dominance columns of the two eyes in area 17 of the occipital lobe, leading to loss of fine stereopsis.33 The statistically significant differences between the responses of Lang-Stereotests I and II in the video game group (highly significant absence of stereopsis on the Lang-Stereotest I and positive response to the Lang-Stereotest II) might be explained by the fact that, in contrast to the Lang-Stereotest II, the Lang-Stereotest I has no monocular reference. The presence of one monocularly visible target (star) most likely facilitates binocular vision,34 also leading to higher recruitment of ocular dominance columns in areas 18 and 19 of the striated occipital cortex.
Similar to the video game group in this study, Ancona et al.35 found random-dot stereopsis on the Lang-Stereotest II in several cases with small-angle strabismus without motor fusion and large regional suppression, but not on the Lang-Stereotest I. These forms of small-angle strabismus form a diagnostic entity that is different from microtropia as described by Lang.29 The latter is due to a hereditary predisposition of the alteration of binocular cells in areas 17 and 18, resulting in total lack of random-dot stereopsis with 100% specificity on the Lang-Stereotests.36 However, if the finding of differing results between the two Lang-Stereotests in the same patient, as encountered in both the current study and the study by Ancona et al.,35 may be interpreted as a consequence of functional suppression of stimuli from the non-dominant eye at the brain level, these cases could be diagnosed as “functional” microtropia. In contrast to microtropia by Lang,29 in which the visual system has reached an equilibrium, the functional forms might experience a loss of fusion associated with transient diplopia and, subsequently, acute strabismus.37,38 It is interesting to note that even a small monocular stimulus separate from the perfectly hidden figures of a random-dot stereotest facilitates stereopsis in a similar way to contour stereotests.34,39
The easy-to-perform Lang-Stereotests, which are indispensable for the diagnosis of microtropia40 and in screening for binocular disorders,41–44 made it possible to discover this important feature. Furthermore, the comparison of the differing results between the two versions of the Lang-Stereotest could be useful for the study of stereopsis in stressing conditions (eg, video game playing), help with the diagnosis of the proposed syndrome, and eventually give us more information about the cerebral mechanisms of stereopsis.
Fourth, visual defects were more frequent in the dominant eye of patients in the video game group. During examination in relaxed accommodation, reduced visual acuity in the dominant eye was found that could not be improved by correction.45 Additionally, the refractive errors found were more pronounced in the dominant eye. The higher the speed needed for playing video games, the greater was the effort required from the dominant eye to achieve the best performance in the shortest amount of time possible. Interestingly, reduced visual acuity often improved in cycloplegia, regardless of the nature of the visual defect.
The question of whether these findings reflect an effect on the accommodative system due to the increased effort made by the dominant eye through video game play remains unanswered, but it seems conceivable that the effects of the different strains made by the two eyes might result first in the dominant eye. This could explain the finding that the video game group had a high prevalence of refractive errors, particularly in the dominant eye. Previous studies indicated that the larger brain representation of the preferred eye10,32,46 would be even more relevant in situations in which the dominant eye performs a demanding visual task. Indeed, studies performed on adult patients with amblyopia have shown significant functional improvements if the preferred eye was covered and the amblyopic eye was trained by playing a video game for a short period of time. The positive results of this treatment might be explained by an increase of impulses to the brain from the amblyopic eye, leading to a partial reduction of the imbalance between the representation on the ocular dominance columns of the two eyes, despite the eventual and partial loss of brain plasticity in these adult patients.8
Fifth, a surprisingly large number of patients with an astigmatic defect in the dominant eye was found. This might be explained by the increased mechanical compression exerted by the contracted eyelid muscles during the child's concentration effort on his or her plastic cornea.
Sixth, positive lens prescription for the correction of even minimal values of hyperopia was frequently required. Hence, underdiagnosing of the condition might also result in dependence on spectacles in young children.
For obvious reasons of methodology, these observations could not be answered by the structure of the study. For example, no baseline data prior to the use of video games were obtained and the direct comparison of the low and high electronic use subgroups, which included electronic screens with different properties such as the size of images, movements, contrast glare, and the distance from eye viewing, could be confusing. Furthermore, data considering estimated playing time and parent-reported symptoms could have been biased by the perceptions of parents. Therefore, prospective studies will be needed, possibly in probands who were not yet exposed to video games and with increased exposure times according to a dose–effect paradigm. Even if the data and methodology of the study may be regarded as preliminary, the work describes some interesting findings and hypotheses that merit further in-depth research, including data from age-adjusted cohorts of children not exposed to video games. The results indicate that, although video games seem to improve the visual performance of adults,7,8 the constant use of video games in children may have an adverse effect on their visual system, which is more subject to modification by the stimuli received due to its neuroplasticity.10,11 Among all screen-type activities, video games are the source of stimuli that may cause the greatest and shortest-term alterations because they involve all brain functions rapidly and repetitively.
This study had two aims: to draw the attention of pediatric ophthalmologists to the clinical features accompanying frequent video game use in children and subsequently prevent erroneous diagnostic and therapeutic maneuvers, and to stimulate further research. Recognizing these symptoms can improve the clinical approach, provide relief for the young patient's visual system, avoid unnecessary worries for parents, and circumvent the loss of time and money for inappropriate diagnostic tests in the assessment of headaches and general symptoms. More in-depth studies of these alterations are needed to improve understanding of the complexity of the visual system.