Smartphone use eminently associated with Computer Vision Syndrome Sequelae: Hindawi publication
Digital technologies are now universal and have spread worldwide; thus, digital behaviour has dramatically changed peoples' lifestyles. Computer vision syndrome (CVS) is also called by other names as digital eye strain (DES), occupational asthenopia, digital asthenopia, and video display terminal syndrome (VDTS).
CVS ocular symptoms include visual blur with an underlying mechanism that is not fully understood, dry eye disease (DED), eye redness and irritation, eyestrain, fatigue, discomfort, difficulty in refocusing the eyes, and diplopia. CVS extraocular symptoms include headache; sleep disturbances; depression; musculoskeletal aches, such as neck/ shoulder/back pain; difficulty in writing or holding objects; and pain in thumbs, fingers, or wrists because of tendonitis and/or arthritis.
Smartphones are used extensively worldwide by people of all ages and are characterised by a close viewing distance, related high-definition resolution, thousands of time-consuming applications and games in stores, and 24/7 Internet connectivity. Smartphone usage is thought to be responsible for the sharp rise in CVS prevalence and severity among users, including paediatric populations.
A study was carried out by Mohammed Iqbal and team where primary goal was to document the potential visual and ocular sequelae among medical students using a subjective CVS questionnaire and a complete ophthalmic examination. Furthermore, the secondary goal was to calculate the CVS prevalence within the study cohort.
This study was designed as a cross-sectional case-control study that included 733 medical students. All students completed a specially designed and validated CVS questionnaire survey (CVS-F3). Students from the control (No-CVS) and CVS groups underwent comprehensive ophthalmic examinations including the mfERG (multifocal electroretinography) examinations. The main outcome measures included uncorrected and corrected distance visual acuity (UDVA and CDVA, resp.) measurements, subjective and cycloplegic refractions, slit-lamp examination, intraocular pressure measurement, pupillary reflexes tests, ocular movements' tests, dry eye disease tests, and fundus and mfERG examinations.
CVS-F3 documented that 87.9% of the surveyed students had one or more ocular and/or extraocular complaints. However, only 70.8% of them reported that these complaints were associated with their screen use, i.e, during or immediately after screen-use.
The most common ocular symptom included blurred vision in 40.9% of students, while the most common extraocular symptom was headache (46.8%). All ocular and extraocular complaints worsened with prolonged screenhours, except for depression (P = 0.2).
Student complaints became worse with prolonged screen-hours at night than during the daytime. All ocular symptoms became worse with an increase in the number of screen-years, except for eye strain and redness (P = 0.10 and 0.49, resp). Sleep disturbance (insomnia) was the only extraocular symptom that worsened with the number of screen-years (P = 0.001)
The survey outcomes revealed that the most common screen used by students was a smartphone. In addition, 504 students (68.8%) used various types and systems of smartphones. Laptops were the second most common screen used by the students, reported by 129 users (17.6%). All ocular and extraocular symptoms were significantly higher in students who used smartphones compared with those students who used laptops and desktop monitors.
CVS-F3 demonstrated that there was no statistically significant difference between Android and Apple smartphone users regarding the mean CVS number of symptoms (P = 0.36).
The most common associated screen behaviour CVS factors recorded by CVS-F3 were a close eye-screen distance (42.6% of surveyed students), watching the screen in the dark (33.7%), improper gaze angle as the screen edge was at/above horizontal eye level (28.2%), texting with both thumbs (28.8%), small font size (23.9%), and poor or improper lighting conditions (20.9%).
The study discovered statistically significant differences between students who were texting with both thumbs (n = 211) and the students who were not texting with both thumbs (n = 522) regarding joint pains in wrists and fingers, inability to hold objects well, and difficulty writing with a pen as these extraocular symptoms were worse with texting with both thumbs (all P < 0.0001). These findings suggest that texting with both thumbs represented the mean causative screen related CVS factor linked to the development of joint pains in wrists and fingers, with an inability to hold objects well, and difficulty in writing with a pen.
The mean sphere, cylinder, and SE were significantly higher in the CVS than in the control group (P < 0.0001). These findings suggest that refractive errors, myopia, and astigmatism were risk factors associated with CVS occurrence. Both UDVA and CDVA were significantly better in the control than in the CVS group (P < 0.0001). Both TBUT and Schirmer test showed significantly reduced means in the CVS than in the control group (P < 0.0001
The mfERG subgroup included 40 eyes of 40 students (16 males and 24 females). In the control group, all 20 eyes exhibited a normal mfERG examination with normal foveal responses, including a preserved foveal peak (first positive peak, P1), and the amplitude density (AD) was within the normal range, demonstrating normal foveal function. In the CVS group, only three eyes exhibited a normal foveal response, while the remaining 17 eyes exhibited a reduced foveal response and were identified as positive cases.
Prolonged and continuous screen-hours require the bilateral use of both sets of intraocular and extraocular muscles (e.g., ciliary, constrictive pupillae, and medial recti muscles) to adjust the focus and achieve the best visual performance. Poor eye coordination or inadequate eye focusing might be caused by improper or extremely close viewing distance, improper screen brightness, poor screen resolution, screen-glare in old screens, and/or uncorrected refractive errors, which finally increase CVS severity. The small screen size and small font size also increase eye strain and fatigue due to inadequate eye focusing.
The researchers observed that the distance between the screen and the user's eyes decreases as the screen size decreases and the severity of CVS increases. Therefore, the greatest CVS severity was associated with misuse of smartphones, whereas the lowest severity was associated with desktop computers.
The study concluded, "Subjective questionnaire surveys alone, without an ophthalmic examination, are not ideal for documenting true CVS prevalence. CVS can be only accurately diagnosed with comprehensive ophthalmic examinations and investigations. The misuse of smartphones, regardless of the manufacturer, was the main aetiological agent responsible for the development and sequelae of CVS. Our study showed that CVS might have caused mfERG changes with reduced foveal responses; however, this potential screen-induced foveal dysfunction and its impact on visual acuity need to be confirmed in future studies."
Source: Mohammed Iqbal, Omar Said , Ola Ibrahim and Ashraf Soliman ; Hindawi Journal of Ophthalmology