The cross-sectional study was initiated during lockdown period in the month of April 2020 and after attending online classes for five months, in the month of August 2020. The institution ethical approval was obtained from the Institutional Ethics Committee (Redg. No. ECR/1192/Inst/MP/2019). The present study was carried out in a new medical college running in second year and only two batches available with a total strength of 330 students attending classes through online mode from the last five months during COVID-19 pandemic.

Inclusion and Exclusion criteria: Students who had equal to or more than 80% attendance were included in the study. Students having any eye disorder, using eye drops frequently and those who are not able to attend online classes regularly due to network issues, inadequate mobile data, not having smartphones, electricity issues were excluded from the study.

Total of 280 undergraduate medical students from 1^st and 2^nd professional between age group of 18-25 years were selected for the study out of which 135 were girls and 145 were boys. After full explanation of the structured questionnaire form through online mode, students were provided a Google form with a pre-designed and pre-tested anonymous student feedback questionnaire (Annexure attached) by sending a link through WhatsApp and asked to fill the form and submit it within one hour. Students responded to the questions measuring their perception based on the symptoms experienced in the last 5 months related to DVS which are caused due to two mechanisms: (i) accommodative mechanism; (ii) ocular surface mechanism. The data were collected which includes demography, refractive errors, duration of exposure to digital screen utilised only for reading and attending online lectures during COVID-19 pandemic as well as the size of screen used during learning process.

The authors measured students’ overall perceptions of ocular symptoms through questions which are based on two potential mechanisms such as accommodative mechanism and ocular surface mechanism. Authors used Likert 5 point scale (never, rarely, occasionally, frequently, always) to measure students’ perceptions of ocular symptoms. The research questions which were measured were:

Accommodative mechanism: We measured students perception related to accommodative mechanisms responsible for development of smartphone vision syndrome by using a five-point Likert scale which includes five items like blurring, eye straining, heaviness in the eyes, tiredness and headache. A higher mean score indicates students’ perception for development of smartphone vision syndrome based on the symptoms experienced related to accommodative mechanisms after using a digital screen for attending online classes and study.

Ocular surface mechanism: Ocular surface mechanisms like redness, burning sensation, watery eyes and ocular pain were measured by using a 5-point Likert scale and interpreted that high mean score leads to progression towards DES.

The association between development of ocular symptoms and risk factors like distance of eyes from the screen and refractive errors was analysed. Authors also analysed the impact of duration (1-3 hrs/day, 3-5 hrs/day and more than 5 hrs/day) of digital screen usage on the development of smartphone vision syndrome as well as we assessed the impact of size of digital screen (laptop/computer screen vs smartphone) on development of smartphone vision syndrome.

Both mechanisms were compared using Exploratory Factor Analysis (EFA) to observe item loading patterns. Descriptive statistics were used for the data screening analysis and found to be acceptable, that is, they had an acceptable reliability (Cronbach’s alpha >0.6). The reliability and Content Validity Index (CVI) analysis was carried for accommodative mechanism and ocular mechanism out on the scale comprising five and four items respectively. Cronbach’s alpha showed the questionnaire to reach acceptable reliability, α=0.889 and CVI is 0.721 for accommodative and α=0.812 and CVI is 0.769 for ocular mechanism and both are satisfactory. Kaiser-Meyer-Olkin measure of sampling adequacy is 0.829 and 0.789 which is rated very high for both mechanisms. Sampling adequacy was found to be good. Bartlett’s test of sphericity was used to test the null hypothesis - that the variables in the population matrix were uncorrelated. Both samples had a significance level of p<0.001, indicating that the hypothesis was rejected, and meaning that the strength of the relationship among variables was strong. It was thus suitable to proceed to factor analysis for the data.

Total 280 students participated in the present study with mean age (20.36±1.30) between 18-25 years, out of which 219 students were using smartphones for reading and attending online classes and 61 students were using large screen. In [Table/Fig-1], the descriptive statistics data are means±SD (n=280). A higher item score (range 1-5) indicated the severity. The data analyzed were scored as 1=Never, 2=Rarely, 3=Occasionally, 4=Frequently, and 5=Always. As per the response of the individual students “Never”=1%, “Rarely” =24%, “Occasionally”=46%, “Frequently”=24% and “Always”=5%. About 75% of the total students score range between occasionally to always which indicates that the majority of the students got DVS.

[Table/Fig-2] presents a correlation matrix which shows the significance (p<0.001) in both the cases. The correlation of all items in the ocular mechanism shows better association and in accommodative mechanism except blurring, other shows better association.

In [Table/Fig-3], (184 and 96) a one factor solution was supported by the percentage of variance accounted for by each factor. In both cases, the factor accounted for 57% and 64% of the variance. The second factor in both cases accounted only for an additional 14% each of the variance, and subsequent factors independently accounted for progressively lower percentages of variance.

As most of the participants were using smartphone for online academic activities during lockdown period, 184 students were visualising the digital screen from distance less than arm and forearm length while 96 students from distance greater than arm and forearm length. [Table/Fig-4] presents correlations in both the parameters (accommodative and ocular surface mechanisms) with the different dependent variables such as distance from the screen and refractive errors was analysed in which distance from the screen and different accommodative and ocular mechanisms responsible for DVS have not shown strong correlation but they show the positive and negative correlation with each symptoms related with DVS and correlations were significant (p<0.01 and p<0.001).

Out of 280 participants, 75 were reading for 1-3 hours, 144 for 3-5 hours and 61 for more than 5. Prevalence of ocular symptoms depending on duration of exposure to screen was calculated by ANOVA and the calculated value of F is greater than tabulated. It means the variability observed in these durations per day use of digital platform only for reading and attending lectures online in the last 4-5 months are not by chance and it can be attributed to the effect of duration and it represents that effect on the eyes increases as duration increases [Table/Fig-5]. In [Table/Fig-6], with regard to size of screen associated with DVS symptoms, calculated value of F is greater than tabulated. It means the variability observed in these small and large screen groups are not by chance and it can be attributed to the effect of the small screen on the eyes more than the large screen.

Eye strain due to continued digital screen viewing has become a worldwide problem. This is accompanied by an increase in our dependance on portal and handheld digital screens. In fact, smartphones have become so popular in adolescence that right from school going age an individual has at least one or more of these digital devices. The usage of social media has increased exponentially to disturbing levels. But in the last five months due to COVID-19 pandemic, students all over the world including medical students have been forced to attend classes through online mode which has increased additional load on the eyes for learning and reading purposes. So, the purpose of this study was to evaluate the impact of online usage of digital screens in undergraduate medical students from I^st and II^nd year attending online classes and the risk of developing of smartphone vision syndrome during COVID-19 Pandemic. In younger age groups the strain is lesser while reading printed material when compared to digital screen [17]. The present study showed 75% of the students perceived the overall ocular symptoms as measured on Likert scale. Thus was similar to the previous study by Iqbal M et al., which showed 86% of medical students using digital screen to suffer from one or more of CVS manifestations [7]. Another study by Akinbinu T and Mashalla Y, showed the impact of digital screen usage for more than 3 hours to develop one or more symptoms of CVS in bank employees [18].

The correlation indicates that the students keeping the screen close to eyes (less than arm and forearm length) are prone for the development of DVS and the students keeping the screen at distance (more than arm and forearm length) are less prone to develop DVS. In case of refractive error, the negative correlation shows that the students wearing spectacle (n=150) are less associated with DVS and students with emmetropic eyes (n=130) are significantly associated with DVS.

With regard to distance at which digital screen was kept while attending online classes and reading soft copy, students who kept less distance (less than arm and forearm length) are at higher risk of smartphone vision syndrome development. This association in respect to accommodative and ocular mechanisms agrees with the findings shown by Abudawood G et al., and Rosenfield M, [4,12]. In the present study, refractive errors showed no significant association with DES as shown in previous studies by Abudawood G et al, [4]. However the impact of wearing glasses due to ocular complaints in the study was found to be less than those students who were emmetropic. This could be due to less use of accomodative mechanisms in students wearing glasses while using digital screens. A similar report was also shown by Raja AM et al., who found that ocular complaints were more in the subjects without glasses [19].

As students are using the digital screens regularly for online classes, we assess the duration of digital screen used and revealed that accommodative and ocular mechanisms responsible for development of smartphone vision syndrome was significantly affected as duration of exposure to digital screen increases which was also reported by Bergqvist UO et al., Hassan HMJ et al., Noreen K et al., and Shantakumari N et al., [15,20-22].

However, ocular pain is a symptom commonly related to raised intraocular pressure and glaucoma, It is possible that this symptom could be due to tightness of the eyelid from dry eye. However, the chance of an actual increase in IOP cannot be debarred since the close viewing of small text on a small screen (as during smartphone use) increases the accommodation demands [23] which are linked with an increase in IOP [24,25].

This study was a cross-sectional investigation performed in a single institute with the ocular complaints analysed based on student response without any opthalmic examination.

This research was conducted in a pandemic time where medical education forced globally to shift to online teaching mode which puts additional load on eyes for attending online classes regularly from the last 5 months. The results indicated that the students attending online classes are more prone to development of smartphone vision syndrome. This study had shown association between DVS and the risk factors associated with it: duration of exposure, refractive errors, distance from the screen and size of screen used. The overuse of smartphone could be precursor of raised intraocular pressure and irreversible loss of vision due to glaucoma need to evaluate furthermore in larger group and in longer duration of study. As colleges constantly build up their instructive strategies, there is a need to raise mindfulness students to understand the impact of digital screen viewing for long duration. This will help in preventing the risk of developing smartphone vision syndrome.