INTRODUCTION

More than 20 years ago, a syndrome has been described that encompasses several ocular discomforts associated with the use of devices with digital screens¹this condition is known as visual computational syndrome²or digital visual fatigue (DVF)¹. It encompasses symptoms such as dry eyes, pain, burning and some extraocular symptoms such as cervical pain^3,4. It is a prevalent problem reported in up to 89.9% of students who spend 2 hours or more a day viewing digital screens⁵.

To detect DVF, subjective methods are described, such as self-report surveys, as well as objective methods with various ophthalmological techniques¹. Among the surveys, one of the first was developed by Hayes et al. that evaluated the severity of DVF in office workers⁶. Various studies used this survey approach to evaluate the severity of symptoms and frequency of the syndrome in various areas^4,7making it one of the most reproducible surveys to study DVF. Later, Seguí et al. described another survey for the presumptive diagnosis of DVF⁸. There are more surveys, created by different authors and designed for different age groups^9,10.

Due to the Covid-19 virus pandemic¹¹many students carried out their education virtually, increasing the use of technology¹²and making them a particularly vulnerable population for DVF. Currently, there is no clear definition of DVF. Evaluating prevalence is a challenge due to the various methodologies used for its identification; the surveys used have different approaches when defining a case of DVF. The heterogeneity between the surveys does not allow an adequate comparison of their frequency among different populations⁹. Therefore, the present study aims to measure the frequency of DVF, with the objective of evaluating the degree of agreement between two surveys used for the presumptive diagnosis of DVF among university students.

METHODS

RESULTS

502 surveys were collected. 277 surveys were filled out in paper format and 225 in digital format. 157 did not meet the inclusion criteria, 35 of them belonged to the group of respondents using the printed format. A total of 345 surveys were analyzed.

Among those included, the mean age was 20, 1 years (± 1.59). 53.3% (184) of the participants were women. 48.1% (166) of the participants belonged to the human medicine career. 48.7% (168) reported wearing glasses permanently. The most frequent refractive disorders were myopia (49.6%) and astigmatism (40%). The detailed description of the characteristics is shown in the Table 1.

Regarding the presumptive diagnosis of DVF, the survey by Hayes et al. identified 48.4% (167) as DVF positive, while the Seguí survey classified 71.6% (247) as DVF positive. The most frequently reported discomfort was visual fatigue (83.1%) on the Hayes scale and burning eyes (70.7%) on the Seguí scale. The least reported discomforts were blurred vision at a close distance according to the Hayes scale (45.8%) and double vision on the Seguí scale (23.8%) (Table 2 y 3).

In frequency analysis, 159 (46.1%) of participants tested positive for a diagnosis of DVF by both methods and 90 (26.1%) of participants tested negative for both surveys as well.

In the agreement analysis, the kappa coefficient obtained a value of 0.37 (CI 0.2 - 0.5) in the group of women, the lowest of all. The highest kappa value obtained was that of the career analysis, excluding human medicine, with a value of 0.55 (CI 0.4 - 0.7). In the global analysis of agreement, a value of 0.45 (CI 0.4 - 0.5) was obtained. The frequencies of DVF according to the type of survey used and the different values of the kappa coefficient are detailed in Table 4.

DISCUSSION

This is the first study carried out to evaluate the degree of agreement between diagnostic methods for DVF in university students. We found a degree of agreement of 0.37 in the stratum of women, this indicates an acceptable degree of agreement. In the other strata and the global analysis the values were between 0.41 and 0.6, indicating a moderate degree according to the classification of Landis and Koch¹⁴. This shows that the measurement of DVF is somewhat complex.

Both surveys assess the reported discomfort of DVF, but they do not take into account the same components to define the syndrome and often do not coincide in some symptoms. In addition, the approach between surveys is different, Hayes et al. uses a Likert scale while Seguí's Rachs-based CVS-Q scale assesses only the frequency and intensity of complaints.

Hayes' method identified 48.4% of students as positive for DVF, the most frequently reported discomfort was visual fatigue. Similar results were obtained in the study by Rashmi et al. where a prevalence of 55.83% was found in students of a health career. They found a higher frequency in women (53.7%) as in our study. However, among the most frequently reported symptoms were headache (73%), dry eye (63.33%) and burning sensation of the eyes (53.3%)⁷. An interesting fact is that within the study by Hayes et al, like our study, they described eyestrain as the most frequent eye symptom (96%) among respondents within an office workplace in 2007⁶.

With Seguí's CVS-Q survey, we found a prevalence of 71.6%, burning eyes was the most frequent symptom among students. Similar results were seen in the study by Gammoh et al. where they evaluated a university population in Jordan in 2021, finding a prevalence of DVF (94.5%) using the same method. In addition, students reported tearing more frequently (59%)¹⁵. Likewise, in Peru, Fernandez D. found a frequency of 61% in 200 university students, in addition, he found that the devices mostly used were laptops (57%) and cell phones (37%)¹⁶.

Although we focus on the analysis of these 2 diagnostic methods by surveys, there are studies such as the one by Mowatt et al., where they related ergonomic habits and the frequency of DVF through a survey designed and validated by themselves. They evaluated 409 students and found that 63% had severe DVF syndrome. Interestingly, musculoskeletal complaints were included in the questionnaire, with neck pain (75.1%) being found most frequently as part of the DVF¹⁰.

The difference in the characterization of DVF through self-reported clinical symptoms could be the explanation for the concordance levels. Hayes originally designed a survey for an office setting, and its objective was to assess severity rather than a diagnosis of DVF⁶, was subsequently applied to different contexts such as a university environment⁷. On the other hand, the survey used by Seguí provides us with a more extensive characterization of the syndrome as well as a lower cut-off point to speak of a positive case⁸. Therefore, if one or the other survey is to be applied in presumptive diagnostic settings or frequency studies, we recommend the application of Seguí's CVS-Q survey.

The sample was considered representative for the university, therefore, we can conclude that, in this context, the prevalence of DVF was high and that it should be considered as a potential public health problem especially in young adults due to the increasing exposure to digital screens for academic, work or recreational reasons. In addition, a high prevalence of refractive disorders such as astigmatism was evident. Similar findings were obtained in the study conducted by Wangsang K. in Thailand where he found a significant association between astigmatism and a positive diagnosis of DVF (p = 0.041)¹⁷. DVF is also described in children, however, self-reporting methods would not be optimal and the characterization of DVF in this age group is different¹⁸.

Limitations

The study has limitations, one of them was the different survey modality of the study participants. First, the survey was applied physically in printed formats; it was evident that there were problems understanding the instructions at the time of filling out the Seguí survey, so the virtual filling modality was changed through Google Forms. To address this limitation, a stratified analysis of agreement by survey modality was performed. Another limitation was the possible poor understanding of some symptoms such as the visualization of colored halos or the sensation of a foreign body. Likewise, the Hayes survey did not offer the same validation parameters as the Seguí survey, thus limiting further points of comparison between both methods.

CONCLUSION

In conclusion, the surveys by Hayes et al. and Seguí's CVS-Q, although they share the same objective of measuring the frequency of DVF and through the same self-report method, showed acceptable agreement for the detection of DVF in women and moderate in the other strata and at a global level, thus showing that they do not have the same approach when dictating a presumptive positive diagnosis of DVF.

With these data, we recommend promoting optimal vision care among populations such as university students and encouraging DVF research to implement timely management. The diverse association with other health problems such as vision accommodation problems and constant headaches¹⁹make its detection a priority. Recommendations can be as simple as ergonomic practices to the use of special focusing lenses²⁰.