Effects of artificial tears on ocular surface symptoms and visual task performance in digital device users

Abstract

This prospective, single-arm study investigates the effects of preservative-free artificial tears on ocular symptoms, visual task performance, and tear film stability in visual display terminal (VDT) users. Thirty VDT users with digital eye strain and dryness symptoms were prescribed preservative-free artificial tears four times daily for one month. Ocular Surface Disease Index (OSDI) and Computer–Vision Symptom Scale (CVSS17) questionnaires were collected at four visits (screening, initial, one week and one month). Blink rate and eye fixations during six simple computer tasks and out-loud reading speed were determined before and after computer use. Noninvasive tear film break-up time (NIBUT) and tear meniscus height (TMH) were also recorded. VDT users’ symptoms [CVSS17 (35.70 ± 3.72 to 27.27 ± 4.43; P < 0.01); OSDI (19.99 ± 3.20 to 10.52 ± 6.04; P < 0.01)] improved after artificial tear use at final visit. Out-loud reading speed did not significantly change, although a slight improvement in the normalized value was observed after computer use between the initial (0.99 ± 0.13) and final (1.02 ± 0.15; P < 0.01) visits. No significant differences between visits were found in the blink rate, eye fixations, NIBUT or TMH. Preservative-free artificial tears effectively reduce subjective symptoms in VDT users, although this relief does not translate into measurable improvements in visual task performance or tear film metrics.

Introduction

The number of activities requiring prolonged use of visual display terminals (VDTs) is on the rise^1,2. Moreover, VDTs such as computers, laptops, smartphones, tablets, and e-readers have become indispensable tools for personal, professional, and academic tasks. Digital device users often experience a range of computer-related eye and visual symptoms, collectively described as computer vision syndrome or digital eye strain (DES),³ which can significantly impact their quality of life and productivity^4,5. This condition is estimated to affect approximately 60 million people worldwide, with an annual incidence of one million new cases⁶.

Many VDT users report asthenopia symptoms (eye strain, tired eyes, or headache), ocular surface symptoms (eye dryness, ocular redness, and itching or tearing, among others), visual disturbances (double vision or blurred vision), or extraocular discomfort (head, neck or back pain)^3,6. DES symptoms are particularly prevalent among those who spend more than 4 h a day on digital screens⁷. To quantify these symptoms, validated questionnaires are available for the detection of DES, and the Computer–Vision Symptom Scale (CVSS17) questionnaire is one of the most commonly used^8,9 instruments, as it classifies symptom severity into five distinct levels⁸.

In recent years, scientific evidence has consistently revealed a significant association between dry eye disease (DED) and computer use^10,11. Despite describing distinct conditions, DED and DES share relevant symptoms, suggesting that risk factors for one condition may be associated with the other. However, as the use of displays in workplaces continues to grow, the prevalence of DED among VDT users remains uncertain. Based on a recent meta-analysis, the overall prevalence of DED in digital device users is estimated to be approximately 49.5% (9.5%–87.5%).¹¹

Artificial tears are the first approach for managing DED¹² and are considered in DES participants to lubricate the ocular surface and increase tear volume, thereby reducing symptoms⁶. Nevertheless, data assessing the role of artificial tears in reducing DES symptoms are limited⁶. Moreover, research has demonstrated that DED is associated with reduced visual efficiency, leading to decreased productivity in workers and longer reading speed¹³. It is conceivable that DES participants may experience similar effects.

On the other hand, lubricants reduce surface friction during blinking, thereby improving dryness symptoms and lubricating the ocular surface, which helps alleviate discomfort¹³. The aim of this study was to assess the effects of preservative-free artificial tears on symptoms related to DES, visual task performance and tear stability in VDT users.

Methods

Participants

A prospective, single-arm study was designed to be conducted at the University of Valladolid between January and June 2023. The Human Sciences Ethics Committee of Valladolid Area-Este Clinic Hospital (Castilla y Leon Public Health System-SACYL) approved this study, which followed the tenets of the Declaration of Helsinki. All participants signed informed consent forms. A sample size of 30 participants was required to detect a difference of 4.5 points in the Ocular Surface Disease Index (OSDI) questionnaire¹⁴ with P = 0.05 and 80% power.

Participants aged between 18 and 55 years who attended all visits, experienced eye discomfort related to VDT use (CVSS17 score ranging from 29 to 42 points, corresponding to stages 3 and 4)⁸ and with eye dryness [Ocular Surface Disease Index (OSDI)¹⁵ score ranging from 13 to 24] were included. Additionally, the participants were required to use screens for more than 4 h a day and have good best-corrected visual acuity [LogMar ≤ 0.00 for distance, intermediate (60 cm) and near (40 cm) vision]. All participants underwent a comprehensive optometric examination, including both objective and subjective refraction, to confirm that they achieved their best-corrected visual acuity with their habitual refractive correction when needed. Participants performed the computer tasks using their habitual refractive correction, in cases where glasses were required. Participants who had received systemic administration of drugs potentially affecting the ocular surface, topical administration of medications known to alter the ocular surface, contact lens wear, or artificial tears or lubricants within 7 days prior to inclusion in the study (screening visit), as well as those with any other ocular pathology or binocular conditions causing discomfort (e.g., heterophoria, accommodative, and eye movement disorders) identified through comprehensive ocular examination or history of previous ocular trauma or surgery, were excluded.

Study outcomes

All participants who agreed to participate in the study were administered the CVSS17 and OSDI questionnaires to assess symptoms related to DES and DED, respectively^8,15. The CVSS17 provides information on approximately 15 different symptoms, including a symptom’s severity and frequency and the subject’s opinion. The DES can be classified into 5 levels according to the total score, with level 1 corresponding to an absence of symptoms and level 5 corresponding to very severe discomfort related to the use of digital screens⁸. The CVSS17 questionnaire is composed of 17 questions, which provide a total score ranging from 17 to 53 points (the higher the score is, the greater the patient’s DES symptoms)⁸. The OSDI questionnaire is structured into three main domains: ocular symptoms (5 questions), vision-related daily function (4 questions) and environmental triggers (3 questions)¹⁵. The OSDI score ranges between 0 and 100, where higher scores represent greater severity of symptoms¹⁵.

Computer-based visual task performance was assessed via eye tracker technology (Gazepoint GP3HD, Gazepoint, Vancouver, Canada) during all the study visits; the blink rate and the number of eye fixations per minute were recorded (Gazepoint Control software UX edition v6.10.0). A 19-inch flat screen monitor with a native 1280 × 1024 resolution was set up with the Gazepoint GP3 HD eye tracker placed below the screen on a small tripod. The eye tracker was configured via Gazepoint Control software to run at 150 Hz with default settings and accuracies of 0.5–1 degree and 0.1 spatial resolution. Following the manufacturer’s recommendations, the participants were positioned 65 cm from the monitor with their eyes aligned with the top third of the screen and were asked to move their head and eyes naturally throughout the study. No chinrest or headrest was used. The room conditions were kept consistent across all visits, including uniform lighting and the absence of visual or acoustic distractions, to ensure optimal reliability of the recordings.

The out-loud reading speed was determined using a 77-word International Reading Speed Text (IReST)¹⁶ shown on a computer screen. The out-loud reading speed was measured by assessing the number of words read per minute (wpm) and the normalized value (dividing the wpm by the mean speed expected for IReST texts). Eight different IReST texts of similar reading difficulty were chosen to evaluate changes in out-loud reading speed before and after computer-based visual tasks (pre-tasks and post-tasks) and between visits (before and after artificial tear use).

The participants engaged in various computer-based visual tasks that required different degrees of concentration and attention, with an estimated total duration of approximately 30 min: (1) out-loud reading speed using an IReST text; (2) sustained silent reading speed using a 600-word passage; (3) watching an animated movie clip; (4) four psychotechnical tests presented randomly, involving tasks that required medium attention (counting geometric shapes and finding pairs of numbers that add up to 10) and high attention (detecting word equalities and image localization); (5) and finally, out-loud reading speed using an IReST text.

Finally, tear film stability was assessed with noninvasive break-up time (NIBUT), the moment when the tear film breaks on 5% of the ocular surface (TBT5%), and tear meniscus height (TMH) measurements collected with the MYAH device (Topcon, Tokyo, Japan) before and after computer tasks at all study visits. Measurements of tear film stability were conducted on both eyes, beginning consistently with the right eye. TMH was measured first, followed by NIBUT, in order to minimize reflex tearing.

Study procedure

The study comprised a total of 4 visits (recruitment, initial, follow-up, and final visits; Fig. 1) that were scheduled at the same time for each subject to minimize the day-to-day variability of the tear film. The single-arm design without a control group is mitigated by the inclusion of two pre-treatment visits (recruitment and initial), which serve to confirm the stability of symptoms over time and ensure that participants fully understood the questionnaire items. This approach helps reduce the likelihood of random or inconsistent responses and strengthens the reliability of the baseline data. All participants were required to use digital screens for at least 4 h per day throughout the study period, including the intervals between visits, to ensure consistent exposure and minimize variability in screen-related symptomatology. Screen time was self-reported by participants and was not actively monitored.

Fig. 1 [Images not available. See PDF.]

Flowchart of the study procedure. OSDI = Ocular Surface Disease Index questionnaire; CVSS17 = Computer-Vision Symptom Scale questionnaire; NIBUT = noninvasive break-up time; TMH = tear meniscus height.

At the recruitment visit (Day − 7), all participants who agreed to be enrolled in the study were given the CVSS17 and OSDI questionnaires. Those participants who met the inclusion criteria and none of the exclusion criteria and agreed to participate in the study underwent a complete eye examination, including computer-based tasks and checking that the usual refraction used by them was the correct one.

All questionnaires and computer-based visual tasks were repeated one week later at the initial visit (Day 0) to control for any possible learning effects in evaluating visual tasks with the eye tracker system and to confirm the patient’s symptoms. If, at the initial visit, the patient continued to meet all the inclusion criteria and none of the exclusion criteria, preservative-free artificial tears in single-dose vials (Systane Ultra UD, Alcon SL, Geneva, Switzerland) were prescribed for use four times per day.

At the one-week follow-up visit (Day 7) and the final visit (Day 30), the full protocol—including the battery of computer-based visual tasks and tear film stability assessments—was repeated. During these visits, NIBUT, TBT5%, and TMH measurements were taken at three different time points to evaluate the short-term effects of artificial tears. First, baseline measurements of NIBUT, TBT5% and TMH were performed before instilling any artificial tears and prior to computer use. Then, one drop of Systane Ultra UD was instilled, and the same measurements were repeated to assess the immediate effect of the drop, still before the computer task. Finally, after completing the visual task on the computer, a third set of NIBUT, TBT5% and TMH measurements was taken to evaluate changes following screen exposure. The questionnaires were not administered at the one-week follow-up visit, as CVSS17 is designed to assess symptoms occurring during the preceding 4 weeks. Therefore, it was decided not to administer either questionnaire at that visit.

Statistical analysis

Statistical analysis was performed via SPSS for Windows software (version 27.0; SPSS, Inc., Chicago, IL, USA) and Microsoft Office Excel (Microsoft Corp., Washington, USA). The parametric data distribution was verified with the Shapiro-Wilk test (P < 0.05 indicated that the data were nonparametrically distributed). The results are summarized as the means ± standard deviations (SDs) and 95% confidence intervals (CIs). For non-normally distributed data, results are presented as median and interquartile range (IQR). A repeated-measures analysis of variance (ANOVA) or nonparametric Friedman test for repeated measures was used, as appropriate, to examine the significant differences in the results across the four visits (post hoc pairwise comparisons were performed via Bonferroni correction). Pairwise comparisons were assessed with adequate correction according to the data distribution (Wilcoxon or paired t test) to determine the differences between the pre-task and post-task measurements and the changes in the study variables after the use of artificial tears. P values of less than 0.05 were considered statistically significant.

Results

A total of 34 subjects were initially enrolled in the study (11 men and 23 women). No adverse events were reported during the study period. Four participants were excluded: two did not complete the final visit questionnaires or had incomplete measurements recorded by the eye tracker system, and two voluntarily withdrew from the study. Therefore, the final sample included 30 participants (11 men and 19 women) with a mean age of 28.8 ± 7.6 years (range 19 to 43 years).

DES and dryness symptoms

Figure 2 shows the results of the CVSS17 and OSDI questionnaires conducted at different visits. There were no statistically significant differences in CVSS17 (Paired t-test, P = 0.17) and OSDI (Wilcoxon, P = 0.67) scores between the recruitment and initial visits, suggesting that participants’ symptoms remained consistent before starting artificial tear use (Table 1). On the other hand, after one month of Systane Ultra UD use, symptoms improved significantly, as did both DES (CVSS17: Paired t-test, P < 0.01) and dryness symptoms (OSDI: Wilcoxon, P < 0.01).

Fig. 2 [Images not available. See PDF.]

Summary of the CVSS17 and OSDI questionnaire scores at the different study visits. Median, 95% CI and post hoc comparison p values are presented for each variable. OSDI = Ocular Surface Disease Index questionnaire; CVSS17 = Computer-Vision Symptom Scale questionnaire, D = Day.

Table 1. Results from the CVSS17 and OSDI questionnaires across the different study visits.

	Recruitment Mean ± SD Median (IQR)	Initial Mean ± SD Median (IQR)	Final Mean ± SD Median (IQR)	P value
CVSS17	35.23 ± 3.26 35.00 (4.00)	35.70 ± 3.72 35.50 (4.25)	27.27 ± 4.43 27.00 (8.00)	< 0.01*
OSDI	20.06 ± 2.92 20.82 (4.11)	19.99 ± 3.20 20.83 (6.09)	10.52 ± 6.04 9.09 (9.83)	< 0.01**

*Repeated-measures analysis of variance (ANOVA). **Nonparametric Friedman test.

Tear film stability measurements

With respect to NIBUT, TBT5% and TMH, no significant differences were found between visits (Table 2). As expected, after instilling the drop of artificial tears at the follow-up and final visits, there was a significant increase in the TMH (Wilcoxon, P < 0.01), which returned to baseline values after completing the computer tasks (Table 2).

Table 2. Descriptive data of noninvasive tear breakup time (NIBUT), time to reach 5% tear break-up (TBT5%), and tear meniscus height (TMH) measured at each visit at three time points: (1) before instillation of artificial tears and prior to the computer task, (2) after instillation of one drop of systane ultra UD and before the computer task, and (3) after completing the computer-based visual task.

Study visit	Computer pre-tasks		Computer post-tasks (3) Mean ± SD Median (IQR)	P Value*
	Before drop instillation (1) Mean ± SD Median (IQR)	After drop instillation (2) Mean ± SD Median (IQR)
	NIBUT
Recruitment	2.95 ± 2.06 1.80 (2.63)	–	2.79 ± 2.30 1.80 (1.40)	0.67
Initial	3.10 ± 1.97 2.45 (2.53)	–	2.60 ± 1.64 1.80 (1.80)	0.14
Follow-up	3.34 ± 3.35 2.20 (2.48)	3.41 ± 3.25 2.00 (2.65)	3.62 ± 5.14 1.70 (1.78)	0.87
Final	3.67 ± 3.51 2.25 (3.07)	3.62 ± 3.62 2.10 (3.17)	4.35 ± 5.52 2.20 (3.70)	0.75
P Value	0.38	0.80	0.48
	TBT5%
Recruitment	10.26 ± 7.07 8.92 (7.56)	–	9.22 ± 6.99 8.35 (6.46)	0.20
Initial	10.25 ± 6.16 8.56 (6.45)	–	8.70 ± 5.80 7.49 (4.55)	0.08
Follow-up	10.37 ± 7.20 8.24 (6.15)	11.03 ± 8.75 8.65 (11.10)	10.37 ± 8.82 7.16 (9.46)	0.98
Final	10.59 ± 8.06 8.45 (9.47)	10.47 ± 8.78 7.10 (12.65)	10.42 ± 8.75 8.68 (8.93)	0.82
P Value	0.75	0.92	0.75
	TMH
Recruitment	0.26 ± 0.11 0.24 (0.14)	–	0.27 ± 0.13 0.24 (0.18)	0.75
Initial	0.27 ± 0.13 0.24 (0.19)	–	0.26 ± 0.12 0.25 (0.19)	0.65
Follow-up	0.24 ± 0.09 0.22 (0.12)	0.42 ± 0.22 0.37 (0.24)	0.28 ± 0.12 0.26 (0.19)	< 0.01**
Final	0.26 ± 0.11 0.26 (0.16)	0.43 ± 0.29 0.35 (0.19)	0.26 ± 0.12 0.24 (0.16)	< 0.01**
P Value	0.10	0.40	0.59

SD = standard deviation, IQR = interquartile range. * Friedman test results comparing study visits; ** Wilcoxon post-hoc comparison revealed nonstatistically significant differences between measurements before drop instillation and after the computer task.

Computer-based visual task efficiency

No statistically significant change was found in the blink rate or eye fixations per minute during any of the eight computer visual tasks included in the study after one month of artificial tear use (Table 3). It was observed that tasks requiring less concentration had a higher blink rate. With respect to the out-loud reading speed, no statistically significant differences were found with the use of artificial tears (Table 4). However, a slight but statistically significant improvement (Paired t-test, P = 0.01) in the normalized value of the reading speed postcomputer tasks was found after one month of artificial tear use (Fig. 3).

Fig. 3 [Images not available. See PDF.]

Summary of the normalized out-loud reading speed values at the different study visits, measured before (pre-tasks) and after (post-tasks) computer use. Median, 95% CI and post hoc comparison p values are presented for each variable. Words/Min = words per minute; D = Day.

Table 3. Descriptive data of number of blinks per minute (blink frequency) and number of eye-fixations in each visual task performed in all study visits. Median and interquartile range (IQR) are reported for blink frequency due to its non-parametric distribution, while mean and standard deviation (SD) are reported for eye fixations given their parametric distribution

Visit	Initial out-loud reading speed Mean ± SD Median (IQR)	Sustained silence Mean ± SD Median (IQR)	Watching a video Mean ± SD Median (IQR)	Counting geometric shapes Mean ± SD Median (IQR)	Finding pairs of numbers Mean ± SD Median (IQR)	Word equalities Mean ± SD Median (IQR)	Image localization Mean ± SD Median (IQR)	Final out-loud reading speed Mean ± SD Median (IQR)
BLINKS PER MINUTE
Recruitment	11.0 ± 8.1 10.4 (14.5)	11.3 ± 8.4 11.5 (7.3)	15.1 ± 9.5 13.4 (17.2)	10.2 ± 7.4 8.3 (11.8)	8.6 ± 7.0 5.9 (6.1)	6.0 ± 5.1 5.0 (5.4)	3.0 ± 5.0 0.0 (5.2)	11.1 ± 8.7 7.5 (13.7)
Initial	11.8 ± 5.6 13.1 (8.8)	11.9 ± 5.8 13.1 (9.7)	15.9 ± 7.9 18.6 (16.0)	11.8 ± 5.4 12.4 (8.6)	8.5 ± 5.4 8.6 (7.9)	7.3 ± 5.3 7.0 (6.1)	4.9 ± 5.8 1.3 (10.9)	11.0 ± 7.7 10.9 (0.3)
Follow-up	13.3 ± 8.6 11.0 (15.1)	13.8 ± 9.2 13.2 (16.2)	15.6 ± 10.0 13.4 (19.9)	13.0 ± 7.1 13.5 (11.7)	9.9 ± 7.7 8.9 (9.3)	7.6 ± 5.4 6.6 (8.6)	5.1 ± 5.5 4.4 (8.7)	13.5 ± 9.3 13.6 (14.7)
Final	13.6 ± 6.7 15.7 (12.7)	13.1 ± 8.5 15.5 (15.1)	15.4 ± 9.7 14.6 (13.8)	12.7 ± 8.3 11.8 (13.6)	8.3 ± 6.2 8.2 (10.1)	6.7 ± 5.4 6.4 (7.6)	2.8 ± 3.6 0.0 (4.4)	13.7 ± 7.6 14.3 (8.8)
P Value*	0.32	0.21	0.95	0.83	0.55	0.31	0.16	0.31

EYE-FIXATIONS PER MINUTE
Recruitment	154.8 ± 25.2	178.9 ± 30.0	149.6 ± 13.4	152.4 ± 14.7	105.6 ± 37.9	129.7 ± 28.4	178.8 ± 28.3	154.1 ± 20.1
Initial	154.6 ± 15.5	183.3 ± 16.2	151.3 ± 11.1	153.8 ± 10.4	103.3 ± 28.2	131.0 ± 21.5	181.0 ± 18.7	157.3 ± 17.4
Follow-up	156.8 ± 15.4	182.6 ± 24.7	149.2 ± 15.3	153.7 ± 11.7	106.2 ± 24.0	127.4 ± 19.6	175.2 ± 19.8	153.4 ± 9.0
Final	154.4 ± 14.7	180.1 ± 14.7	151.6 ± 14.1	150.9 ± 13.9	102.1 ± 26.3	127.5 ± 16.2	176.2 ± 20.7	154.7 ± 20.1
P Value**	0.95	0.86	0.87	0.81	0.95	0.89	0.74	0.84

*Friedman test results assessing blinks per minute across study visits for each test. ** ANOVA results comparing study visits by eye-fixation per minute for each test.

Table 4. Descriptive data of the words per minute (WPM) and normalized value of reading speed (words per minute obtained divided by the expected words for each of the IReST texts used shown in parentheses) measured at each visit before and after performing the visual tasks with the computer.

	Computer pre-tasks Mean ± SD		Computer post-tasks Mean ± SD		P Value (pre-tasks Vs. post-tasks)
Visit	WPM (standard value)	Normalized value	WPM (standard value)	Normalized value	WPM	Normalized value
Recruitment	203.93 ± 23.33 (202)	1.01 ± 0.12	204.64 ± 23.57 (208)	0.98 ± 0.11	0.13	0.15
Initial	221.52 ± 27.61 (219)	1.01 ± 0.13	221.68 ± 28.83 (225)	0.99 ± 0.13	0.93	0.06
Follow-up	219.25 ± 28.10 (216)	1.02 ± 0.13	232.30 ± 27.77 (229)	1.01 ± 0.12	0.05	0.34
Final	222.14 ± 30.68 (216)	1.03 ± 0.14	221.67 ± 33.26 (218)	1.02 ± 0.15	0.77	0.12

SD = standard deviation.

Discussion

There is a notable connection between the increase of VDT use and the appearance of symptoms typical of DES, including burning sensations, blurred vision, and dryness¹⁷. DES symptoms may impact more than half of the individuals who spend more than four hours daily in front of a digital screen, potentially leading to considerable economic consequences⁷. Recent research indicates a high incidence of DES among university students and lecturers in Spain, with a prevalence rate of 65.4%.¹⁸ Similarly, recent reports revealed that 65% of American adults¹⁹ or 62.6% of adults who work with digital devices in the United Kingdom and Ireland²⁰ suffer from some form of DES after extended use of electronic devices. On the basis of current research, artificial tears are often suggested to alleviate the ocular symptoms of DES^12,17. Generally, studies analyse changes in symptoms related to dry eye but not the symptoms secondary to VDT use with specific questionnaires for this purpose. Therefore, the efficacy of artificial tears in mitigating DES remains uncertain, as very few studies have directly investigated this issue^{21, 22–23}.

This study assessed the use of preservative-free artificial tears for addressing DES complaints and revealed significant improvements in CVSS17 and OSDI scores after one month of treatment with preservative-free artificial tears four times per day compared with the baseline visit scores (Fig. 2). These results provide evidence of the beneficial effect of artificial tears based on HP-Guar and hyaluronic acid for the management of ocular and DES symptoms in VDT users. The statistically significant reductions in symptom scores observed after one month of Systane Ultra UD use appear to be clinically meaningful (Table 1). These changes represent a shift from moderate to mild symptom severity, suggesting a tangible improvement in patient comfort. In contrast, symptom scores remained stable between the recruitment and initial visits, when artificial tears were not used, reinforcing that the observed improvements are likely attributable to the intervention. Therefore, the changes in questionnaire scores not only reached statistical significance but also reflect a clinically relevant reduction in DES symptoms.

Only one previous study has analysed the symptoms related to DES and the use of the same preservative-free artificial tears used in our study. Talens-Estarelles et al.²² evaluated the change in DES symptoms during 30 min of computer use with the instillation of one drop of Systane Ultra in a group of participants who had undergone laser in-situ keratomileusis (LASIK) surgery and a control group of healthy participants. They reported that DES symptoms measured with the CVS-Q questionnaire during 30 min of computer use was reduced at the visit in which they used artificial tears in both control (4 ± 4 versus 2 ± 3; P = 0.01) and LASIK participants (4 ± 4 versus 2 ± 4; P < 0.01). Furthermore, a reduction in both the frequency and severity of dry eye symptoms was observed following the computer task when artificial tears were used. However, participants with significant DES symptoms were not included in this study.

Another study conducted by the same research group²⁴ investigated the effects of computer and smartphone reading tasks on dry eye symptoms in healthy participants wearing contact lenses, with and without the instillation of one drop of Systane Ultra, two minutes before reading. When assessing the influence of contact lens wear, participants reported more post-task dry eye symptoms (measured by the OSDI and DEQ-5) when reading on both devices than before the task. Finally, when the effect of artificial tear instillation during contact lens wear was examined, the results indicated no significant difference in dry eye symptoms when reading on either device (P ≥ 0.68). Nevertheless, the direct impact on DES symptoms was not evaluated.

Trancoso Vaz et al.²¹ in 2023 evaluated the efficacy of ergoophthalmological measures combined with preservative-free hyaluronic acid artificial tears (Hyabak, Thea) applied to both eyes four times a day for the short-term management of the signs and symptoms of dry eye and DES before and after prolonged computer use in video gamers during a 3-day video gaming session (≥ 6 h per day). There was no statistically significant difference in Standard Patient Evaluation of Eye Dryness Questionnaire (SPEED) score between the first and third days of the study (P = 0.46) when artificial tears and ergoophthalmological measures were used. However, subjective evaluation of symptoms indicated significant reductions in ocular fatigue and dryness.

Artificial tears have demonstrated efficacy in regulating the interval between blinks and alleviating eye discomfort during computer use²³. The impact of digital device use on the ocular surface is linked to the cognitive demand of the task and the associated reduction in blinking frequency. To the best of the authors’ knowledge, this is the first study in which the blink rate and the number of fixations per minute in symptomatic VDT users performing computer tasks requiring different levels of concentration have been assessed after the use of artificial tears. In our study, the use of artificial tears improved symptoms but did not appear to affect the blink rate or the number of fixations that users must perform when working on the computer in the short term and after one month of artificial tear supplements use. In line with previous studies,²⁵ tasks requiring greater attention result in a lower blink rate. Although scientific evidence shows that the blink rate decreases with high cognitive demands, it is similar across different electronic devices (computers, laptops, e-readers, or smartphones)²⁶ and when hard-copy materials are used²⁷. Previous studies have suggested that the eye discomfort experienced by VDT users may be linked to a higher percentage of incomplete blinks rather than an actual decrease in the blink rate,^25,27 indicating that future research should explore this topic further.

Despite the decrease in symptoms, the participants did not experience an increase in tear film stability following artificial tear usage. No significant differences in NIBUT, TBT5% or TMH were found after one month of artificial tear use. In line with these results, a previous report²² also reported no significant differences in the NIBUT measured after 30 min of computer tasks in healthy participants who used artificial tears. Moreover, no significant changes in the TMH were found with the use of artificial tears. As expected, after one drop was instilled at the follow-up and final visits before performing the computer tasks, the TMH increased considerably, but after performing the computer tasks, it returned to the initial values. Sabucedo-Villamarin et al.²⁸ investigated short-term changes in TMH and NIBUT following the use of artificial tears, ocular baths, and eyelid wipes in a healthy population. Their findings revealed a temporary increase in TMH after the application of artificial tears and ocular baths, while eyelid wipes had no effect. Consistent with our results, none of these interventions produced immediate changes in NIBUT. In contrast, other studies have noted an increase in tear volume and symptoms of dry eye following the use of digital displays^22,29. This contradictory finding described in the literature may be explained by the fact that, occasionally, a burst of blinking can occur after performing tasks on digital screens, which can increase tear volume³⁰. Another possible explanation is that tear composition may influence both NIBUT and TMH, as formulations with higher viscosity or lipid content can enhance tear film stability and prolong retention on the ocular surface. Since the artificial tears used in this study are based on hydroxypropyl-guar, it is plausible that different components could yield distinct outcomes²⁸.

For the change in out-loud reading speed, it should be noted that this is the first time that this change has been analysed after the use of artificial tears in symptomatic VDT users. There are no previous studies of a similar nature to compare the results, but it has been shown that dry eye disease is associated with slower out-loud and silent reading speeds^13,31. To evaluate reading speed in the present study, IReST texts were used. Although these are standardized texts and comparable between visits, the number of words read per minute depends on the specific text chosen and its average reading speed. Therefore, a standardized value was used to avoid potential bias in the choice of texts. A comparison of the change in reading speed with the use of artificial tears revealed only a slight increase in reading speed post-task at the final visit in symptomatic VDT users (1.02 ± 0.15 versus 0.99 ± 0.13; P = 0.01). However, the use of the artificial tears in this study did not seem to have a prominent effect on the reading speed of participants with DES.

This study has several limitations that should be highlighted. A control group of VDT users who did not present symptoms related to DES was not included. This would have helped to determine whether the reading speed or blink rate is different in asymptomatic versus symptomatic VDT users. It is also not known whether the symptoms would also have changed in the control group; however, a recruitment visit, and an initial visit were made to determine the consistency of the responses to the questionnaire. Another limitation of this study is that the exact number of hours participants spent using screens was not monitored. Although they were required to use a computer for at least 4 h per day, it would have been valuable to record precise screen time in order to more accurately evaluate whether a direct relationship exists between the duration of screen exposure and the outcomes observed. Additionally, the study lacked formal monitoring of participant compliance with the artificial tear instillation regimen. While subjects were given specific instructions regarding usage, adherence was not verified, which may have introduced variability in the results. Another potential limitation is the learning effect that participants may experience when performing repeated computer-based tasks. This could influence parameters such as blink rate or number of eye fixation per minute, potentially affecting the consistency of measurements across sessions. Moreover, the study environment was not fully controlled. Minor fluctuations in temperature or humidity may have influenced certain measurements, particularly those related to tear film stability or ocular comfort. The impact on tear film stability (NIBUT or TMH) after 30 min of computer use was assessed, which may not be representative of work task durations of digital device use. The results could differ if more time was spent performing computer tasks. Nevertheless, this computer task duration of 30 min aligns with prior research that revealed significant changes in dry eye signs following this duration of computer use^22,32,33. It would also have been interesting to compare whether the improvement in DES symptoms with the use of assessed artificial tears is comparable to the effects that artificial tears from different commercial brands or compositions would produce. Despite these limitations, the current study sets the stage for future research aimed at evaluating the impacts of artificial tears on enhancing symptoms related to DES.

Conclusions

Preservative-free artificial tears (Systane Ultra UD; prescribed 4 times per day) for 30 days significantly reduce digital eye strain symptoms but do not improve objective visual task performance or tear film stability in digital device users.

Author contributions

Conceptualization, S.O.-T., I.S. and R.M.; methodology, S.O.-T., I.S. and R.M.; validation, S.O.-T., I.S. and R.M.; formal analysis, S.O.-T., I.S. and R.M.; investigation, S.O.-T., I.S. and R.M.; resources, S.O.-T., I.S. and R.M.; writing—original draft preparation, S.O.-T., I.S. and R.M.; writing—review and editing, S.O.-T., I.S. and R.M.; visualization, S.O.-T., I.S. and R.M.; supervision, S.O.-T. and R.M.; project administration, S.O.-T. and R.M. All authors have read and agreed to the published version of the manuscript.

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests. Supported by an investigator-initiated study grant from Alcon (IIT#73376825).

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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