Dry eye disease is a multifactorial disease of the tears and ocular surface that causes discomfort, visual disturbance and tear film instability, with increased osmolarity of the tear film and inflammation of the ocular surface [1]. It is one of the most common reasons for visiting an eye clinic. Population studies have reported a prevalence of between about 5% and more than 30%, depending on the population and the definition used [2-4], with higher rates in Asian populations [5-7]. Hospital-based studies from India have also found dry eye to be common [8,9].

The use of computers, laptops and smartphones has increased dramatically in India over the past decade, particularly among students and workers in the information technology sector. Computer vision syndrome describes the eye and vision symptoms related to prolonged computer use, and dry eye is one of its main components [10]. Studies from Delhi and Chennai have reported a high frequency of visual symptoms among computer professionals and students [11,12]. Chennai is a major information technology centre with a hot and humid climate, but many computer users work in air-conditioned offices.

Several mechanisms link screen work with dry eye. The blink rate falls markedly during computer work [13,14], and incomplete blinks become more frequent [15,16]. The wider palpebral aperture when looking straight at a screen increases tear evaporation [17], and low humidity in air-conditioned offices adds to it [18]. Meibomian gland dysfunction [19] and reduced lacrimal secretion [20] have also been described in screen workers. In Japan, dry eye was common among office workers who used visual display terminals [21-23], and visual display terminal users showed changes in tear film characteristics [24]. There are few such studies from Indian hospitals. The aim of this study was to estimate the prevalence of dry eye disease among computer users attending a tertiary care hospital in Chennai and to determine its association with daily screen time and other risk factors.

Study design and setting This hospital-based cross-sectional study was conducted in the Department of Ophthalmology, Sri Muthukumaran Medical College Hospital & Research Institute, Chennai, a tertiary care teaching hospital. Written informed consent was obtained from every participant. Participants Consecutive patients aged 18 to 45 years attending the ophthalmology outpatient department who had used a desktop or laptop computer for at least 2 hours a day for at least 1 year were enrolled. Patients were excluded if they wore contact lenses, had undergone ocular or refractive surgery, had active ocular infection, allergy or inflammation, eyelid abnormalities, glaucoma, or systemic disease associated with dry eye such as diabetes, thyroid disease, rheumatoid arthritis or Sjogren syndrome, or used systemic or topical drugs known to affect tear production. Contact lens wearers were excluded because contact lens wear independently affects the tear film [23]. Sample size Because the prevalence of dry eye among Indian computer users was uncertain, an expected prevalence of 50% was used to obtain the largest sample. With an absolute precision of 9% and a 95% confidence level, the formula n = Z² p (1 - p) / d² gave a minimum of 119 participants, and 120 were included. Data collection A structured questionnaire recorded age, sex, occupation, total duration of computer use in years, average daily screen time, frequency of breaks, working in an air-conditioned environment, use of spectacles, and the distance and position of the monitor relative to the eyes. Daily screen time was grouped as 2 to 4 hours, more than 4 to 6 hours and more than 6 hours. Assessment of dry eye Symptoms were assessed with the Ocular Surface Disease Index (OSDI), a validated 12-item questionnaire scored from 0 to 100 [25]; a score of 13 or more was taken as symptomatic. After recording visual acuity and slit lamp examination, the tests were done in the following order, with 5-minute intervals between them, in a room with stable temperature and humidity. Tear film break-up time was measured after instillation of fluorescein with a moistened strip, as the mean of three readings, and a value below 10 seconds was considered abnormal [26]. Ocular surface staining with fluorescein was graded by the Oxford scheme [27]. The Schirmer I test without anaesthesia was performed with standard strips placed at the junction of the lateral and middle thirds of the lower eyelid for 5 minutes, and wetting of less than 10 mm was considered abnormal. The right eye was used for analysis. Dry eye disease was diagnosed when the OSDI score was 13 or more and at least one clinical sign (tear film break-up time below 10 seconds, Schirmer I value below 10 mm in 5 minutes, or Oxford staining grade 1 or more) was present. Severity was graded as mild (OSDI 13 to 22), moderate (23 to 32) or severe (33 or more). Statistical analysis Data were entered in Microsoft Excel and analysed with Python version 3.13 using the SciPy and statsmodels libraries. Prevalence was reported with an exact 95% confidence interval. Categorical variables were compared with the chi-square test and the Cochran-Armitage test for trend, and continuous variables with the independent t-test or one-way analysis of variance. Correlation between daily screen time and clinical test values was assessed with Pearson's correlation coefficient. Variables with p < 0.20 on univariate analysis were entered into a multivariable logistic regression model, and results were expressed as adjusted odds ratios (aOR) with 95% confidence intervals. A p-value below 0.05 was considered significant.

A total of 120 computer users were enrolled. Their mean age was 31.3 ± 7.6 years, and 54.2% were men. Of these, 29.2% were information technology professionals, 35.8% students and 35.0% other office workers. The mean daily screen time was 6.5 ± 2.4 hours, 56.7% used a computer for more than 6 hours a day, and 64.2% worked in air-conditioned offices (Table 1).

Table 1. Characteristics of computer users with and without dry eye disease

SD: standard deviation; IT: information technology. Chi-square test for proportions; independent t-test for means.

Symptoms (OSDI score of 13 or more) were reported by 101 participants (84.2%), and at least one abnormal clinical test was found in 81 (67.5%). Tear film break-up time was abnormal in 44.2%, ocular surface staining in 50.0% and the Schirmer test in 15.8%. Dry eye disease was present in 71 participants, giving a prevalence of 59.2% (95% CI 49.8 to 68.0). Of these, 14 had mild, 27 moderate and 30 severe disease. A further 30 participants (25.0%) had symptoms without abnormal clinical signs. Patients with dry eye had higher OSDI scores, shorter tear film break-up time and lower Schirmer values than those without dry eye (all p < 0.001).

Table 2. Symptom scores and clinical tests by daily screen time

One-way analysis of variance for means; Cochran-Armitage test for trend for proportions. OSDI: Ocular Surface Disease Index.

The prevalence of dry eye increased with daily screen time, from 21.7% in those using a computer for 2 to 4 hours to 34.5% at more than 4 to 6 hours and 82.4% at more than 6 hours (p for trend < 0.001). Mean tear film break-up time fell from 12.4 to 9.1 seconds and mean Schirmer value from 16.7 to 12.7 mm across the same groups (Table 2). Daily screen time correlated negatively with tear film break-up time (r = -0.57, p < 0.001) and with Schirmer I values (r = -0.48, p < 0.001), and positively with the OSDI score (r = 0.43, p < 0.001).

Dry eye was not associated with age, occupation, air-conditioned work environment, frequency of breaks, spectacle use or monitor position (Table 1). On multivariable logistic regression, screen time of more than 6 hours a day was the only independent risk factor (aOR 16.06, 95% CI 4.87 to 53.03; p < 0.001). Screen time of more than 4 to 6 hours, female sex and computer use for 5 years or more were not significant after adjustment (Table 3).

Table 3. Multivariable logistic regression of factors associated with dry eye disease

Variables with p < 0.20 on univariate analysis were entered into the model. OR: odds ratio; CI: confidence interval. Model fit: Hosmer-Lemeshow p = 0.54.

In this hospital-based study of computer users in Chennai, dry eye disease was present in 59.2% of participants, and its prevalence rose sharply with daily screen time, from 21.7% in those using a computer for 2 to 4 hours to 82.4% in those using it for more than 6 hours. Screen time of more than 6 hours a day was the only independent risk factor and was associated with a 16-fold increase in the odds of dry eye. The prevalence in our study is higher than that reported in the general population [2-4] and in Indian hospital-based studies [8,9], which is expected in a group selected for prolonged computer use, more than half of whom used a computer for over 6 hours a day. Dry eye was also common among Japanese office workers who used visual display terminals [21,22]. Differences in the definition of dry eye, the age of the participants and the working environment explain much of the variation between studies. In our study, 25.0% of users had symptoms without abnormal clinical signs, which agrees with the well-known poor correlation between symptoms and signs of dry eye [28]. The OSDI was a useful screening tool, as reported in another Indian study [29]. The dose-response relation between screen time and dry eye in our study is consistent with the known effects of screen work on the tear film. Tsubota and Nakamori showed that the blink rate falls sharply during work at a video display terminal [13], and Patel and colleagues found reduced blinking and tear film stability during visual display unit use [14]. Incomplete blinks increase during demanding screen tasks [15] and when reading from a screen compared with paper [16], and patients with dry eye show a marked reduction in blinking during screen work [30]. In our study, tear film break-up time and Schirmer values decreased progressively with increasing screen time, and staining of the ocular surface rose from 8.7% to 72.1%. Reduced lacrimal secretion [20], meibomian gland dysfunction [19] and changes in tear film characteristics [24] have been described in screen workers, and long working hours were associated with dry eye in the Osaka study [22]. The steep rise above 6 hours a day suggests a threshold beyond which the tear film can no longer compensate. Environmental and personal factors were less important than screen time in our study. Air-conditioned offices with low humidity increase tear evaporation [18], and a monitor placed at or above eye level widens the palpebral aperture and exposes more of the ocular surface [17], but neither was associated with dry eye in our participants, possibly because most worked in similar conditions and the sample was modest. Female sex is a consistent risk factor for dry eye in population studies [2,7]; dry eye was more common in women in our study, but the difference was not significant after adjustment. Studies of computer users from Delhi and Chennai also found that longer daily computer use was associated with eye symptoms [11,12]. These findings have practical implications. Dry eye in computer users is often unrecognised and treated as simple eye strain [10]. Ophthalmologists should ask about screen time in all young patients with ocular discomfort and examine them for dry eye, particularly those who use a computer for more than 6 hours a day. Computer users should be advised to limit continuous screen time, take regular breaks, blink consciously and completely, keep the monitor slightly below eye level, and use lubricating drops when needed. Employers in the information technology sector can support eye health through workstation ergonomics and periodic eye examinations. Strengths and limitations The strengths of this study are the use of a validated symptom questionnaire, a combined definition of dry eye based on symptoms and clinical signs, and the measurement of screen time in categories that allowed a dose-response analysis. It has limitations. It was a hospital-based study with a modest sample, so the participants may not represent all computer users, and the confidence interval of the adjusted odds ratio for screen time is wide. Screen time was self-reported. Tear osmolarity, meibomian gland assessment and blink rate were not measured. The cross-sectional design does not establish cause and effect, and a control group of non-computer users was not included.

Dry eye disease was present in 59.2% of computer users attending a tertiary care hospital in Chennai, and its prevalence increased with daily screen time. Screen time of more than 6 hours a day was the only independent risk factor and was accompanied by reduced tear film stability and tear secretion. Computer users should be screened for dry eye and counselled on limiting screen time, regular breaks, blinking, workstation ergonomics and the use of lubricants.

DECLARATIONS

Acknowledgement: The author thanks the faculty, residents and staff of the Department of Ophthalmology, Sri Muthukumaran Medical College Hospital & Research Institute, Chennai, and all the participants of the study.

Funding: None.

Conflict of interest: The author declares no conflict of interest.

Author contribution: Dr. Deepak Pathak designed the study, examined the participants, analysed the data, wrote the manuscript and approved the final version.

Data availability: The data supporting the findings of this study are available from the corresponding author on reasonable request.