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Table of Contents
ORIGINAL ARTICLE
Year : 2022  |  Volume : 4  |  Issue : 1  |  Page : 35

Dry eye disease related to digital screen exposure in medical students


1 Department of Ophthalmology, All India Institute of Medical Sciences, Gorakhpur, Uttar Pradesh, India
2 Department of Community Medicine and Family Medicine, All India Institute of Medical Sciences, Gorakhpur, Uttar Pradesh, India

Date of Submission08-Mar-2022
Date of Decision20-Jun-2022
Date of Acceptance12-Jul-2022
Date of Web Publication30-Jul-2022

Correspondence Address:
Alka Tripathi
All India Institute of Medical Sciences, Kunraghat, Gorakhpur, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/pajo.pajo_16_22

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  Abstract 


Aim: The aim of this study is to determine the magnitude and severity of dry eye disease (DED) in medical students as per assessed by the questionnaire Ocular Surface Disease Index (OSDI) and Schirmer's test.
Materials and Methods: A cross-sectional study of a 2-month duration involving medical students was conducted to determine the magnitude and severity of DED. Dry eye was assessed through self-administered questionnaire, Schirmer's test, and OSDI scoring.
Results: The most common symptom among the participants was eyestrain in 39% (N = 31) followed by headache in 33% (N = 26). Based on Schirmer's test, 75% (n = 60) of the participants were normal, 8% (n = 6) students had mild DED, 5% (N = 4) students with moderate DED, and 11% (N = 9) students had severe DED. Based on OSDI scoring, 59% (n = 47) participants were normal, 28% (n = 21) had mild DED, 11% (N = 9) had moderate, while 2% (N = 2) had severe DED.
Conclusion: In this era of digitalization, DED has engulfed the younger population who are spending greater hours on different digital devices. The prevalence of symptomatic dry eyes in our study was 41% while it was 25% based on signs. This should raise concern among the caregivers to increase awareness regarding dry eyes and give strict guidelines restricting screen time. The use of ergonomic practices such as appropriate lighting in a room, adjusting digital screen parameters (resolution, text size, contrast, and luminance), and taking frequent breaks while using the screen should be encouraged.

Keywords: Dry eyes, Ocular Surface Disease Index, prevalence, Schirmer's test


How to cite this article:
Tripathi A, Agarwal R, Kharya P. Dry eye disease related to digital screen exposure in medical students. Pan Am J Ophthalmol 2022;4:35

How to cite this URL:
Tripathi A, Agarwal R, Kharya P. Dry eye disease related to digital screen exposure in medical students. Pan Am J Ophthalmol [serial online] 2022 [cited 2022 Aug 11];4:35. Available from: https://www.thepajo.org/text.asp?2022/4/1/35/353003




  Introduction Top


Visual display terminal use is increasingly common in the young population (10–24 years). The young population is more into browsing the web, watching video, group chatting, and social networking (such as Facebook, WhatsApp, and Twitter) as compared to other age groups. Learning has become interactive and much easier. E-books allow one to carry an entire library with them. Smartphones provide an instant entertainment, round-the-clock access to banks, and other facilities such as ticket booking, online shopping, and GPS system. Teaching learning media has also evolved preferring PowerPoint presentations, and interactive smart boards in comparison to older methods such as chalk and board.

Our eyes are not comfortable staring at digital screens all day. Continuous exposure can lead to eyestrain, headaches, blurred vision, difficulty in changing focus between far and near, dryness of eyes, irritated eye, tired eyes, redness, and contact lens discomfort. The neck, shoulder, and backache can also be related to the way we use our eyes on the screen.[1]

Tear Film and Ocular Surface Society Dry Eye Workshop,II TFOS DEWS II defines dry eye disease (DED) as the following: “Dry eye is a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.”[2] The prevalence of DED ranges from 5% to 50%[3] with a moderate-to-severe form of the disease affecting 5%–10% of the population.[4] Meta-analysis by Courtin et al. estimated the prevalence of DED associated with digital screen usage to range from 9.5% to 87.5%.[5]

According to different studies, the relation between digital screen use and DED is due to the fact that digital screen use causes variation in blinking dynamics, leading to DED.[6]

Dry eye is an underdiagnosed cause of ocular morbidity and decreased quality of life (QoL). Reduction in the modifiable risk factors of dry eye can reduce its prevalence. To our knowledge, there are very limited dry eye studies on the younger population in India. Therefore, the present study was conducted with an aim of finding the magnitude and severity of DED among young medical graduates who spend a good amount of time on digital screens.


  Materials and Methods Top


The aim of the study was to find the magnitude and severity of DED as per assessed by the questionnaire Ocular Surface Disease Index (OSDI) and Schirmer's test in medical students. It was a cross-sectional study of a 2-month duration. By considering the overall prevalence of DED as 25%[7] and absolute allowable error as 10%, sample size was calculated by the following formula: N = (Zα/2) 2PQ/D2 Zα/2 = 1.96, P = Prevalence = 25%, D = Absolute allowable error = 10, Q = (100 − P) = 75. Assuming a nonresponse rate of 10%, the sample size was raised to 80%. Hence, the final sample size for the study purpose was 80. Ethical approval was taken from the institutional human ethics committee of the institute. All medical graduates using digital screen for more than 2 h/day for at least 1 year and Medical graduates willing to give prior consent for evaluation were included in the study. Students with gross corneal abnormalities (opacity of any grade, keratoconus, Laser-assisted in situ keratomileusis LASIK surgery), history of allergic conjunctivitis, gross lid abnormalities, blepharitis, contact lens users, and using any topical or systemic medication causing dry eyes (antiglaucoma, antihistaminic) were excluded from the study. Data were recorded on a preform consisting of the following parameters [Annexure 1]. The students were assessed for dry eyes using:

Ocular Surface Disease Index Questionnaire[8]

OSDI scores are used for measuring the severity of dry eye. [8] The 12 items of the OSDI questionnaire are graded on a scale of 0-4, where 0 indicates none of the time; 1, some of the time; 2, half of the time; 3, most of the time; and 4, all of the time. The total OSDI score is then calculated based on the following formula: OSDI = ([sum of scores for all questions answered] × 100)/([total number of questions answered] × 4) [Annexure 2].

OSDI score is bounded between 0 and 100, where 0 represents a healthy eye in terms of ocular surface diseases while 100 represents a patient with severe symptoms of ocular surface disease and could be categorized as normal ocular surface (0–12 units), mild ocular surface disease (13–22), moderate (23–32), and severe (33–100).

Schirmer's test

Schirmer I test (without anesthesia) is performed to evaluate basal and reflex tear secretion. In the Schirmer I test, a filter paper strip Whatman filter paper no 41 (35 mm × 5 mm) was used to measure the amount of tears produced over 5 min. Five millimeter of the Schirmer strip was folded and kept at the junction of lateral one-third and medial two-thirds of the lower eyelids with the eyes open. After 5 min the strip was removed and wetting of the strip was measured. The severity of dry eye was graded as normal when the reading is more than 15 mm, mild dry eye 11–15 mm, moderate dry eye 5–10 mm, and severe <5 mm.[9]

Data collected were analyzed using simple statistical tools by Microsoft Excel 2010 and SPSS Statistical Package for the Social Sciences, Chicago (Ill., USA) (latest version). The Chi-square test was used as a statistical test and P < 0.05 was considered to be significant.


  Results Top


Ninety-five students were approached for the study, out of which 15 were excluded and 80 were enrolled [Figure 1]. About 57.5% (n = 46) of participants were male, while 42.5% (n = 34) were female. The mean age of the students was 20 years ± 1.2 years [Figure 2].
Figure 1: Flow of the participants

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Figure 2: Distribution of participants according to sex

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Fifty-one medical students had refractive error, out of which 61.25% (N = 49) had myopia, while 2.5% (N = 2) had hypermetropia. Thirty-six percent (N = 29) student spent 4–6 h on screen, 30% (N = 24) >6 h, and only 7.5% (N = 6) had screen time of <2 h [Figure 3].
Figure 3: Duration of digital screen use in hours

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The most common symptom among the participants was eyestrain in 39% (N = 31), followed by headache in 33% (N = 26). Eighteen percent (N = 14) students complaint of foreign body sensation, 22% (N = 17) sore eyes, 18% (N = 14) red eyes, 14% (N = 11) blurred vision, and 6% (N = 5) had difficulty in changing focus [Figure 4].
Figure 4: Symptoms among participants

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Schirmer's test showed the severity of DED. Seventy-five percent (n = 60) of the participants were normal. There were 8% (n = 6) students with mild DED, 5% (N = 4) students with moderate DED, and 11% (N = 9) students with severe DED [Figure 5]. The average OSDI score was 16 ± 8.25.
Figure 5: Severity of dry eyes based on Schirmer's test

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Based on OSDI scoring, 59% (n = 47) participants were normal, 28% (n = 21) had mild DED, 11% (N = 9) had moderate, while 2% (N = 2) had severe DED [Figure 6].
Figure 6: Severity of dry eyes based on OSDI score. OSDI: Ocular surface disease index

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The association between Schirmer's test and gender, screen time as well as age was not found to be statistically significant [Table 1]. The association between OSDI score and gender, screen time as well as age was also not found to be statistically significant [Table 2].
Table 1: Association between Schirmer's test and gender, screen time, and age

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Table 2: Association between Ocular Surface Disease Index score and gender, screen time, and age

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Cohen's κ was run to determine if there was an agreement between two observation/diagnostic tests, i.e., dryness of eyes/foreign body sensation and the Schirmer test. There was no agreement between the two observation, κ = 0.051 and P < 0.641 [Table 3]. Similarly, there was no agreement between the two observation/subjective test, i.e., dryness of eyes/foreign body sensation and OSDI score κ = 0.182 and P < 0. 054 [Table 4]. There was no agreement between the two observations by OSDI score and Schirmer test, κ = 0.009 and P < 0.931 [Table 5].
Table 3: Cohen'sk between dryness/foreign body sensation and Schirmer's test

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Table 4: Cohen'sk between dryness/foreign body sensation and OSDI score

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Table 5: Cohen'sk between OSDI score Schirmer's test

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  Discussion Top


The major goal of this study was successfully achieved by estimating dry eye prevalence among medical students at AIIMS, Gorakhpur. According to the TFOS DEWS II epidemiology report 2017, the prevalence of DED ranged from 5% to 50%.[3] The prevalence of signs was higher and more variable than symptoms and there were very few prevalence studies in the younger population and in populations south of the equator. The prevalence of dry eyes as derived from Schirmer's test was 25% in our study which is similar to the study reported by Fayyadh et al. (20.1%).[10] In a study by Titiyal et al.,[11] the prevalence of DED based on the OSDI questionnaire was found to be 32% (5000/15,625) which is less than that found in our study (41%).

In our study, 91.25% (n = 74) of students spent >2 h on digital screens which is higher than found in a study on the Indian population by Dubey et al. which revealed that 68% of adolescents have screen time for more than 2 h.[12] Adolescents are more active on social media and have more inclination toward video games, apps, and Internet surfing which might lead to increasing screen time as well as symptoms of DED. The Indian Academy of Pediatrics[13] as well as the WHO[14] recommends no screen exposure for < of 2 years of age children and in the 2–5 years age group screen time should not exceed 1 h. For older children and adolescents no cutoff limit is given but one has to balance screen time with other physical activities.

The most common symptoms associated with digital screen use in our study were eyestrain 39% and headache 33% which is similar to findings by Reddy et al.[15] The findings are in concordance with American Optometric Association[16] which states that DED is most commonly associated with eyestrain, headaches, blurred vision, and dry eyes. Sheedy et al.[17]described two different mechanisms and sets of symptoms for asthenopia commonly known as eyestrain. External symptoms such as burning, irritation, tearing, and dryness were closely related to the dry eye whereas internal symptoms such as eyestrain, pain, and headache were associated with accommodative insufficiency or binocular vision problems. Portello et al.[18] similarly divided computer-related symptoms into accommodative symptoms (blurred vision at near, blurred or double vision, and difficulty refocusing from one distance to another) and dry eye symptoms (irritated/burning eyes, dry eyes, eyestrain, headache, tired eyes, sensitivity to bright lights, and eye discomfort).

The association between Schirmer's test and gender, screen time as well as age was not found to be statistically significant in our study. This is similar to the study by Akkaya et al.[1] which concluded that long-term computer use did not change the Schirmer test results significantly. This leads to the conclusion that the evaporative mechanism is more prevalent than decreased tear production/release in the dry eyes due to digital screen use. Ozdemir and Temizdemir[19] found no statistically significant difference in the Schirmer test results between the young and older age groups. However, Schirmer test values gradually decreased with advancing age. Tear function tests did not show statistically significant differences according to sex as found in our study. No association was found between symptoms and Schirmer's score in our study. Nichols et al.[20] concluded that dry eye clinical tests are not associated with dry eye symptoms. Schein et al.[21] found no association between Schirmer test and symptom frequency in an elderly sample of about 2240 patients. These tests are more reliable in severe dry eyes patients as found in the study by Bjerrum.[22] The low cost and simplicity of Schirmer's test make it the most commonly used screening test for the assessment of tear production but besides the issue of reflex tearing, the main drawback with the test is that it is not predictive in terms of disease severity, which limits its value as a diagnostic test. Schirmer test performance may be more reliable for more severe diseases than for mild-to-moderate dry eye as found in several studies.[23]

The association between OSDI score and gender, screen time as well as age was also not found to be statistically significant in our study. This is similar to the study by Unlü et al. where no statistically significant correlation was found between screen time and the mean OSDI, tear breakup time (TBUT), and Schirmer's test scores.[24] OSDI-derived prevalence increases with age, being highest among the participants aged >80 years as found in a study by Gupta et al.[25] In our study, the participants were of the younger age group which lead to a statistically insignificant result. No association was found between symptoms and OSDI score in our study. Vitale et al. also found no association of the OSDI subscale and overall scores with ocular surface parameters.[26] The OSDI questionnaire is a reliable and valid diagnostic tool for measuring the QoL and severity of DED and can easily be performed in routine screening as well as in community-based surveys and outpatient departments. However, the OSDI questionnaire assesses only a few dry eye symptoms including sensitivity to light, grittiness, and pain and omits important symptoms such as tearing and foreign body sensation. These drawbacks make the OSDI questionnaire less accurate in terms of assessing specific DED symptoms that the patient may describe. One more disadvantage is that OSDI measures the frequency of symptoms only. Frequency measures a patient's experience of symptoms but it cannot substitute for the severity of the symptoms which patient suffers.[8]

There was no agreement between the two observations by OSDI score and Schirmer test which is consistent with findings of Onwubiko et al.[27] Kyei et al.[28] also found no significant association between Schirmer test and OSDI. Thus, there is a low and inconsistent association between dry eye symptoms and dry eye clinical tests. Premature breakup of the tear film is the root cause of dry eye. TBUT depends on the reduction of surface tension by mucins and other surface-active agents, and therefore, TBUT test is more sensitive for measurement of the stability of the tear film rather than of aqueous tear production. However, the test is invasive and should be performed by experts which limits its use to a clinical setup. The best combination of diagnostic tests for DED is OSDI, TBUT, and Schirmer test (sensitivity 100%, specificity 95%, and accuracy 99.3%) as found by Alves et al.[29]


  Conclusion Top


In the past 20 years, innumerable research and clinical trials have promoted the evolution of the understanding of DED. The newer DED classification recognizes the necessity of symptomatic involvement and the presence of associated ocular surface signs in making a diagnosis of DED. In this era of digitalization, DED has engulfed the younger population who are spending greater hours on different digital devices. The prevalence of symptomatic dry eyes was 41%, while it was 25% based on signs. This should raise concern among the caregivers to increase awareness regarding dry eyes and give strict guidelines restricting screen time. The use of ergonomic practices such as appropriate lighting in a room, adjusting digital screen parameters (resolution, text size, contrast, and luminance), and taking frequent breaks while using screen should be encouraged. The 20/20/20 strategy (after 20 min of digital screen use, focus on objects over 20 feet away for 20 s) is recommended by most the researchers for management of DED. A larger sample size involving equal representation from all age groups can give a better estimate of DED prevalence. Thus we propose a multicentric study design involving newer diagnostic methods for evaluating the actual burden of DED.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.


  Annexure 1 Top


Study pro forma

  1. Name of the student
  2. Age/Sex
  3. Visual acuity
  4. Best-corrected Visual Acuity/Refractory error
  5. Duration of digital screen usage
  6. Symptoms observed:




  7. Eyestrain-Y/N

    Headaches-Y/N

    Blurred vision-Y/N

    Difficulty in changing focus between far and near-Y/N

    Dryness of eyes/grittiness/foreign body sensation-Y/N

    Irritated eyes-Y/N

    Redness-Y/N

  8. OSDI SCORE
  9. Schirmer's test 1



  Annexure 2 Top


Ocular Surface Disease Index Questionnaire





 
  References Top

1.
Akkaya S, Atakan T, Acikalin B, Aksoy S, Ozkurt Y. Effects of long-term computer use on eye dryness. North Clin Istanb 2018;5:319-22.  Back to cited text no. 1
    
2.
Craig JP, Nichols KK, Akpek EK, Caffery B, Dua HS, Joo CK, et al. TFOS DEWS II definition and classification report. Ocul Surf 2017;15:276-83.  Back to cited text no. 2
    
3.
Stapleton F, Alves M, Bunya VY, Jalbert I, Lekhanont K, Malet F, et al. TFOS DEWS II epidemiology report. Ocul Surf 2017;15:334-65.  Back to cited text no. 3
    
4.
Mufti M, Sayeed SI, Jaan I, Nazir S. Does digital screen exposure cause dry eye? Indian J Clin Anat Physiol 2019;6:(1):68-72.  Back to cited text no. 4
    
5.
Courtin R, Pereira B, Naughton G, Chamoux A, Chiambaretta F, Lanhers C, et al. Prevalence of dry eye disease in visual display terminal workers: A systematic review and meta-analysis. BMJ Open 2016;6:e009675.  Back to cited text no. 5
    
6.
Al-Mohtaseb Z, Schachter S, Shen Lee B, Garlich J, Trattler W. The relationship between dry eye disease and digital screen use. Clin Ophthalmol 2021;15:3811-20.  Back to cited text no. 6
    
7.
Patil SD, Trivedi HR, Parekh NV, Jethva JJ. Evaluation of dry eye in computer users. Int J Community Med Public Health 2016;3:3403-7.  Back to cited text no. 7
    
8.
Schiffman RM, Christianson MD, Jacobsen G, Hirsch JD, Reis BL. Reliability and validity of the Ocular Surface Disease Index. Arch Ophthalmol 2000;118:615-21.  Back to cited text no. 8
    
9.
Senchyna M, Wax MB. Quantitative assessment of tear production: A review of methods and utility in dry eye drug discovery. J Ocul Biol Dis Infor 2008;1:1-6.  Back to cited text no. 9
    
10.
Fayyadh IR, Mohammed MA, Abady NH, Tahseen AW, Taleb EN. Dry eye disease among medical students at the University of Fallujah. Ann Trop Med Public Health 2020;23:1038. [Doi: 10.36295/ASRO.2020.231038].  Back to cited text no. 10
    
11.
Titiyal JS, Falera RC, Kaur M, Sharma V, Sharma N. Prevalence and risk factors of dry eye disease in North India: Ocular surface disease index-based cross-sectional hospital study. Indian J Ophthalmol 2018;66:207-11.  Back to cited text no. 11
[PUBMED]  [Full text]  
12.
Dubey M, Nongkynrih B, Gupta SK, Kalaivani M, Goswami AK, Salve HR. Screen-based media use and screen time assessment among adolescents residing in an Urban Resettlement Colony in New Delhi, India. J Family Med Prim Care 2018;7:1236-42.  Back to cited text no. 12
[PUBMED]  [Full text]  
13.
Available from: https://iapindia.org/pdf/Screentime-Guidelines-for-Parents-Ch-005.pdf. [Last accessed on 2021 Oct 28].  Back to cited text no. 13
    
14.
To Grow Up Healthy, Children Need to Sit Less and Play More. Available from: https://www.who.int/news/item/24-04-2019-to-grow-up-healthy-children-need-to-sit-less-and-play-more. [Last accessed on 2021 Nov 05].  Back to cited text no. 14
    
15.
Reddy SC, Low CK, Lim YP, Low LL, Mardina F, Nursaleha MP. Computer vision syndrome: A study of knowledge and practices in university students. Nepal J Ophthalmol 2013;5:161-8.  Back to cited text no. 15
    
16.
American Optometric Association. Computer Vision Syndrome; 2017. Available from: https://www.aoa.org/patients-and-public/caring-for-your-vision/protecting-your-vision/computer-vision-syndrome?sso=y. [Last accessed on 2021 Oct 28].  Back to cited text no. 16
    
17.
Sheedy JE, Hayes JN, Engle J. Is all asthenopia the same? Optom Vis Sci 2003;80:732-9.  Back to cited text no. 17
    
18.
Portello JK, Rosenfield M, Bababekova Y, Estrada JM, Leon A. Computer-related visual symptoms in office workers. Ophthalmic Physiol Opt 2012;32:375-82.  Back to cited text no. 18
    
19.
Ozdemir M, Temizdemir H. Age- and gender-related tear function changes in normal population. Eye (Lond) 2010;24:79-83.  Back to cited text no. 19
    
20.
Nichols KK, Nichols JJ, Mitchell GL. The lack of association between signs and symptoms in patients with dry eye disease. Cornea 2004;23:762-70.  Back to cited text no. 20
    
21.
Schein OD, Tielsch JM, Munõz B, Bandeen-Roche K, West S. Relation between signs and symptoms of dry eye in the elderly. A population-based perspective. Ophthalmology 1997;104:1395-401.  Back to cited text no. 21
    
22.
Bjerrum KB. Test and symptoms in keratoconjunctivitis sicca and their correlation. Acta Ophthalmol Scand 1996;74:436-41.  Back to cited text no. 22
    
23.
Nichols KK, Mitchell GL, Zadnik K. The repeatability of clinical measurements of dry eye. Cornea 2004;23:272-85.  Back to cited text no. 23
    
24.
Unlü C, Güney E, Akçay Bİ, Akçalı G, Erdoğan G, Bayramlar H. Comparison of ocular-surface disease index questionnaire, tearfilm break-up time, and Schirmer tests for the evaluation of the tearfilm in computer users with and without dry-eye symptomatology. Clin Ophthalmol 2012;6:1303-6.  Back to cited text no. 24
    
25.
Gupta N, Prasad I, Jain R, D'Souza P. Estimating the prevalence of dry eye among Indian patients attending a tertiary ophthalmology clinic. Ann Trop Med Parasitol 2010;104:247-55.  Back to cited text no. 25
    
26.
Vitale S, Goodman LA, Reed GF, Smith JA. Comparison of the NEI-VFQ and OSDI questionnaires in patients with Sjögren's syndrome-related dry eye. Health Qual Life Outcomes 2004;2:44.  Back to cited text no. 26
    
27.
Onwubiko SN, Eze BI, Udeh NN, Onwasigwe EN, Umeh RE. Dry eye disease: Concordance between the diagnostic tests in African eyes. Eye Contact Lens 2016;42:395-400.  Back to cited text no. 27
    
28.
Kyei S, Dzasimatu SK, Asiedu K, Ayerakwah PA. Association between dry eye symptoms and signs. J Curr Ophthalmol 2018;30:321-5.  Back to cited text no. 28
    
29.
Alves M, Reinach PS, Paula JS, Vellasco e Cruz AA, Bachette L, Faustino J, et al. Comparison of diagnostic tests in distinct well-defined conditions related to dry eye disease. PLoS One 2014;9:e97921.  Back to cited text no. 29
    


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