A study of the correlation between smartphone usage and dry eye in medical students at a tertiary care center

A study of the correlation between smartphone usage and dry eye in medical students at a tertiary care center Faruqui S.1, Agarwal R.2, Kumar R.3* DOI: https://doi.org/10.17511/jooo.2020.i07.02 1 Saba Faruqui, Assistant Professor, Department of ophthalmology, LN Medical College and JK Hospital, Bhopal, Madhya Pradesh, India. 2 Rahul Agarwal, Professor and Head, Department of ophthalmology, LN Medical College and JK Hospital, Bhopal, Madhya Pradesh, India. 3* Rashmi Kumar, Associate Professor, Department of ophthalmology, LN Medical College and JK Hospital, Bhopal, Madhya Pradesh, India.


Introduction
Ours is a technologically driven generation and digital devices including smartphones are an essential part of our lives. Smartphones are minicomputers that bring the world at our finger-tips.
Besides communication and entertainment, the smartphone has evolved into an important educational tool that provides instant access to reference materials and databases on the go. In the medical field also smartphones serve a vital role in diagnosis, discussion, record keeping, and health education [1][2][3][4][5].
The downside of this digital revolution is that the increased screen-time has a negative impact on ocular health. The small size and distance at which the handheld smartphone screen is used, require increased accommodative effort by the eye muscles which leads to asthenopic symptoms such as blurring, fatigue, dryness, and grittiness which are referred to as Computer vision syndrome (CVS) [6].
Added to that is the reduced blink-rate, which  The questions of dry eye symptoms had 4 possible responses "never", "sometimes", "often" and "always". Subjects who responded to more than 2 of the questions by "always" or "often" were considered positive for symptoms of DED.  The prevalence of DED was found to be 20.81%.

Materials and methods
There was no statistical difference in the prevalence of DED in males and females. The comparison of both groups in terms of their demographic profile and tear film parameters is shown in Table 1. The mean values of all the three tear film parameters were lower in the DED group compared to the non-DED group and the difference was statistically significant as inferred by the student's ttest.  The mean daily usage of smartphones in hours per day was 3.58±1.186. The mean duration of usage in years was 3.195±0.78, ranging from 1-6 years.   were not statistically significant.  The effect of smartphone screen brightness on the DED score is shown in Table 7. The mean DED score in group 1 (<50% screen brightness) was lower than the other 2 groups, and the difference between group 1 and group 3 (automatic brightness setting) was extremely significant statistically with a p<0.001. Not aware 5 ⃰ One way Anova with post-test, comparison between group 1 and 3 is extremely significant with p<0.001 Table 8 shows the effect of protective screen guard against blue light (anti-blue light screen guard), the 22 smartphone users that had anti-blue light screen guard had significantly lower mean DED scores than those who used plain screen guard or anti UV screen guard ( p< 0.0198, by one way Anova).

Discussion
The current study aimed to estimate the prevalence of dry eye and its correlation with the duration of smartphone exposure in hours and years and thus fill the gap in our knowledge about this aspect of smartphone use and ocular health.

Faruqui S. et al: A study of the correlation between smartphone usage
Tropical Journal of Ophthalmology and Otolaryngology 2020;5(7) It was found the prevalence of dry eye disease in smartphones using college students to be 20.  [19][20][21][22]. There are several factors at work that lead to more severe asthenopic symptoms from using the smartphone than the computer screen [6-8]. The smaller screen size coupled with the shorter viewing distance of about 35cm for smartphones, as compared to the normal reading distance of 40cm, requires greater accommodative effort by the ciliary muscles and thus gives rise to eye strain [23].
Another factor is the reduced blink rate reported with the use of any digital visual device such as smartphones, tablets, computer screens, and electronic book readers. This leads to greater evaporation of the tear film and symptoms of dryness and grittiness [24]. The third factor which has been recently studied and found to be of increasing importance in the etiology of smartphone-related dry eye and asthenopia is the blue light emitted by the LED (light-emitting diode) display. This light has a peak emission wavelength of 400-490nm, which is in the blue range [25].
This light is known to cause several adverse effects on the cornea and retina by increasing oxidative and phototoxic damage [9, 26,27]. This could explain the increase in ocular symptoms such as blurring, redness, visual disturbance, and watering on exposure to a smartphone. Additionally, blue light has a damaging effect on the retina and disrupts the melatonin cycle, thus interfering with sleep [28]. The severity of symptoms of CVS also depends on the duration of exposure [29,30]. It was found that higher prevalence and odds ratios of fatigue, heaviness, blurring, photophobia, and dryness in students who used smartphones for more than 3 hours a day. The time spent daily on the smartphone by young people especially has been increasing to dangerously high levels [8,31]. The impact of blue-blocking lenses in spectacles on visual fatigue experienced by digital device users have been explored by several authors [32,33]. It is reported that blue-blocking lenses reduce CVS symptoms after computer tasks [34]. Similar findings were noted in the current study. However, the awareness of blue light-induced ocular damage and the availability of lens coatings and screen filters was found to be low among the present study population as shown in Figures 1 and 2. Similar findings were reported by Sanodia et al [35]. Presently there are not many studies exploring the effect of phone screen brightness on the asthenopic symptoms and tear film parameters. However, experts believe that the ideal screen brightness depends on the ambient light. As a simple rule, the brightness of our gadget should be equivalent to the light surrounding us, such that both the lights' radiance is similar. By doing so, they will blend in, causing the least damage to our eyes.
The current study evaluated the effect of different screen-brightness levels on the DED scores and concluded that <50% setting was the most comfortable, with the lowest DED scores. Many kinds of screen guards or protectors are available, meant to be applied over the smart-phone screen for physical protection from scratches and cracks as well as to curb the reflective nature of the screen to limit the glare on eyes. There is no clinical data on the efficacy of any particular type of screen guard in ameliorating symptoms of eye strain. The present study found significantly lower DED scores in the few users who chose anti-blue screen filters.
limitations Due to the Questionnaire format of data collection, the information gathered could suffer from recall and information bias. Also because the current study population is comprised of medical students from a single institute, there could be selection bias, as the prevalence of CVS and DED may vary with the curriculum and environmental and regional factors.

What does the study add to the existing knowledge
The current study included large sample size and after removing the confounding factors, the current study tried to estimate not only the prevalence of DED but also its association with the duration of exposure. This study has sought answers to thus far unexplored questions about the usefulness of blue light filtering screens and the optimal screen brightness on ocular health.

Conclusion
This study shows that smartphone use increases the symptoms of CVS and DED, even more than computer work and that the duration of exposure plays an important role in the severity of these symptoms.
There is a need to increase awareness about the ergonomic factors such as taking frequent breaks, choosing optimal screen brightness, and use of blue light cutting screens and apps to promote better ocular health.

Author contributions
Dr. Rahul Agarwal: Conceived and designed the study and supervised the project.  Tropical Journal of Ophthalmology and Otolaryngology 2020;5(7)