Technological advances have made a huge impact on almost every aspect of our lives. In particular, the availability of computers has simplified many daily tasks (1–3). The use of digital devices has increased substantially in recent years across all age groups. The extensive daily use for both social and professional purposes has become routine (4). Computers are one of the commonest office tools in various institutions such as government offices and their use has become essential worldwide (5). As a result, workers spend more time looking at computers and other digital devices. However, prolonged use of computers for extended hours causes a range of impairments such as vision-related problems, headaches, and low backache (6).

Computer vision syndrome has been described in various literature sources. The American Optometric Association provides the most widely used definition, stating that “CVS is a group of eye and vision-related problems resulting from prolonged use of computers, tablets, and cell phones” (1). It is a form of repetitive strain disorder that frequently occurs among people using visual display terminals such as computers, tablets, and cell phones for a prolonged duration (7). The level of discomfort has been seen to be proportional to the intensity of computer use (8).

Computer Vision Syndrome has become a growing public health concern often stated the 21st-century’s most common occupational hazard affecting more than 70% of all computer users and it is estimated that around 60 million people worldwide are affected by the problem with a million new cases occurring each year (9, 10) resulting in decreased workplace productivity, lower job satisfaction, higher error rates, and impaired visual ability (11–13). High workload, inadequate accessibility, low utilization of personal protective equipment, and restricted break times when using a computer make the problem of CVS even worse in low-income countries.

While there is no strong evidence for causation, studies have suggested that multiple factors may contribute to the development of this condition. These factors include prolonged exposure to computer screens, environmental factors, and workplace ergonomics (14, 15). The most commonly identified factors that play a role in the development of CVS in different pieces of literature are: Duration of computer use, pre-existing eye illness, knowledge about adverse health effects of prolonged computer use, rest break habits, brightness adjustment, sitting position, and age were significant factors affecting CVS in different pieces of literature (6–8).

Proper lighting is an important factor for visual efficiency and comfort. Consequently, improper lighting is often considered the biggest environmental factor that contributes to visual discomfort (16). There is a paucity of studies evaluating the influence of lighting conditions in the workplace on visual health. Therefore, this study aims to explore the effects of lighting and other ergonomic conditions to improve our understanding of their impact within this context. It attempts to close the gap in the literature by taking measurements such as lighting levels at workstations, and visual distance from monitors to account for environmental and ergonomic factors.

In this study, the prevalence of CVS among employees of Ethio telecom zonal workers was 68.8% [95% CI (64.57–72.9)]. Factors significantly associated with CVS included the habit of taking breaks, adjustment of brightness and contrast, viewing distance <50 cm and improper task illumination.

The prevalence of CVS in this study was closely aligned with other studies: 67.4% among computer office workers in Sri Lanka (7), 72% among computer engineering students in Pakistan (8), 70.4 among university instructors in Ethiopia (14), and 69.5% of computer users in Ethiopia (15). The similarities in this estimates may be attributed to the use of a comparable definition of CVS symptoms.

However, higher prevalences have been reported elsewhere: 89.9% in Malaysia (2), 94.5% in Jordan (16), and 81.0% in Thailand (22). The possible reason for the higher prevalence reported could be that study participants are students the amount of time spent on computers could increase significantly and the habit of taking breaks could be limited as they are more focused on their studies and exams or that they may not have a fixed reading and studying places as they may use any places to study they may study in their dormitories where lighting conditions may not be as appropriate.

Then again, the differences in the tools used to assess CVS and the definition of CVS might be the reason for the variation in prevalence estimates. For example, the study in Jordan used a 16-symptom questionnaire to determine the presence of CVS. In contrast to this, this study used a 10 symptoms questionnaire.

In this study, eye irritation and burning sensation were the most prevalent symptoms reported this is in line with a study among bank workers in Ethiopia (6), and the similarity may be attributed to the comparable exposure status of employees having similar workstations and the similarities in demographics with these working groups.

Blurred vision was another prevalent symptom, reported by 49.1% of the participants. Similarly, it was reported by 45.7% of individuals in a university in Jordan (16). This similarity could be attributed to blurred vision being associated with several other conditions in individuals such as sight problems, astigmatism, and other underlying medical conditions. There is a similarity in the experiences of these two groups where over half of the participants worked with digital devices for at least 4 years or more. This prolonged exposure could perhaps explain the similarities in symptoms (9).

Several studies suggest that females are more likely to develop CVS than males perhaps due to hormonal level differences between female and male as well as female hormonal cycles which impacts evaporation from the tear film (7, 22, 23). Whereas, few other studies show a higher proportion of males developing CVS (6, 10). In this study, however, we did not find a significant difference between males and females.

A substantial proportion of participants in our study were aged below 40. Age was not significantly associated with CVS in this study. However, age is perhaps a known predictor of vision-related problems. As people age, they start to have difficulties of seeing clearly at closer objects, particularly when working with computers. There is a link between chronic conditions such as diabetes and vision; as people get older, they are at risk of developing these conditions, which in turn lead to vision related problems. This relationship is also documented in other studies (24).

In multivariable regression analysis, habits of taking rest breaks was a significant predictor of CVS among participants. Those who regularly took rest breaks were 56.1% less likely to develop CVS compared to those who did not. This finding is in line with other studies showing a similar pattern of decreased risk when taking rest breaks (5, 6, 11, 12, 25). This is perhaps due to increased blinking rates while taking breaks as reduced blinking rates are considered often to lead to dry and irritated eyes (26). In many instances, it is suggested to take micro-breaks during tasks that require sitting in the same posture (13). And the importance of the 20–20-20 rule could never be stressed enough. The American Optometric Society (AOA) suggests adhering to the 20–20-20 rule, which states that you should spend at least 20 s every 20 min gazing at something that is 20 feet away. This enables your eyes to unwind and lubricate more due to greater blinking. Taking frequent pauses can help individuals focus better (1).

In this study, it is seen that participants adjusting brightness and contrast were 61.1% less likely to develop CVS compared to those who did not adjust their brightness. This finding is supported by other similar studies (18, 27). It is suggested to keep screen brightness to match the ambient light. Some modern devices often adjust brightness automatically to match the ambient light using sensors but it is not possible to always rely on this as most devices in an office setting may not have this feature. As for contrast it is often recommended to increase contrast to make the texts that are read outstand the background and hence reduce eyestrain.

In this study, we found a significant association between viewing distance and the development of CVS. Participants who watched their computers from a distance of less than 50 cm were 2.3 times more likely to develop CVS than those who viewed them from a distance of more than 50 cm. There are studies in agreement with this finding (28, 29). The possible reason for this again has to do with the reduced blinking rate when sitting too close to monitors. Between 20 and 40 inches is the optimal distance from your eyes to the screen. The ideal distance for this is roughly an arm’s length. Based on the size and resolution of the screen, you can also determine the appropriate distance. You can sit back in the proper posture without slouching too far back or forward if you have the proper distance between your monitor and your eyes (30).

It was also reported in this study when compared to people who worked under sufficient illumination circumstances (≥200), workers who were working under inadequate task illumination (<200 LUX) had a 1.8 times higher risk of developing CVS. Some studies support this finding (1, 5, 31). Although there is no clear-cut value for the level of illumination, it is recommended to keep office workplaces well-illuminated and not below 200 LUX (19). As described in many instances working under poor lighting conditions can cause eye strain and dry eyes. Perhaps, this is possibly due to the extra load put on the eyes to focus more during poor lighting conditions and as with any other muscles of the body the muscles of the eyes get overworked and tired.

This study aimed to assess the magnitude of Computer Vision Syndrome and identify its possible predictors among Ethio Telecom computer using workers. Consequently, this study reported the prevalence of CVS among employees of Ethio telecom zonal office workers in Addis Ababa was 68.8% [95% CI (64.5, 72.9)]. Moreover, this study identified that habits of taking rest breaks, adjustment of computer brightness and contrast, viewing distance and task illumination levels were significantly associated to CVS.

Limitations in this study arise from the design. Possibly information bias could be introduced such as recall bias where participants might not readily remember symptoms for the major outcome and other variables of the study and Hawthorne effect could also come into play where participants are aware that they are being observed and act in unusual manner. However, steps were taken to minimize this such as explanation of the questions in simple language and allocating sufficient time for responses. In addition, sufficient training was provided to data collectors on the proper use of instruments and data collection.

Recent evidences suggest a link between built environment and visual comfort particularly room design (32). This study did not extensively cover such factors. Future research could investigate the links of CVS and built environment with a focus on room size, design, and lighting conditions besides intensity such as light color and temperature.