|Year : 2020 | Volume
| Issue : 1 | Page : 6-13
Schirmer’s test and tear breakup time in an Egyptian population sample: a hospital-based study
Ahmed A Youssef, Yomna A Alahmadawy, Hany E Elmekkawy, Ahmed M Abdelrahman
Faculty of Medicine, Cairo University, Cairo, Egypt
|Date of Submission||21-Jul-2019|
|Date of Decision||08-Nov-2019|
|Date of Acceptance||05-Dec-2019|
|Date of Web Publication||28-Feb-2020|
MD Yomna A Alahmadawy
3 Montasser Housing, Alharam, Giza 12512
Source of Support: None, Conflict of Interest: None
Background Dry eye is a very common disease in Egypt. Tear film stability and tear secretion are important factors in the assessment of dry eye disease. Schirmer’s test (ST) is used to assess tear secretion, whereas tear breakup time test (TBUT) is used to assess tear film stability.
Purpose The aim of this study was to identify the normative data of the ST and TBUT in a sample of Egyptians and to highlight the variables that may significantly affect these values.
Patients and methods The study included 150 normal healthy participants. They were divided into different groups according to age, sex, residency, and occupation. History was taken from all participants including ocular surface disease index questionnaire. All participants underwent full ophthalmological examination, ST, and TBUT.
Results The mean ST for the population sample was 21.9±9.13 mm, whereas the mean TBUT was 16.04±4.99 s. Studying linear regression for ST with age, sex, occupation, and residency showed that ST was mostly affected by age, where it showed a negative correlation. Studying linear regression for TBUT with age, sex, occupation, and residency showed that TBUT was mostly affected by residency.
Conclusion The study allowed us to take an idea about the normative data of ST and TBUT in an Egyptian population and the effect of different variables on both tests.
Keywords: dry eye, Schirmer’s test, tear film breakup time
|How to cite this article:|
Youssef AA, Alahmadawy YA, Elmekkawy HE, Abdelrahman AM. Schirmer’s test and tear breakup time in an Egyptian population sample: a hospital-based study. Delta J Ophthalmol 2020;21:6-13
|How to cite this URL:|
Youssef AA, Alahmadawy YA, Elmekkawy HE, Abdelrahman AM. Schirmer’s test and tear breakup time in an Egyptian population sample: a hospital-based study. Delta J Ophthalmol [serial online] 2020 [cited 2020 May 31];21:6-13. Available from: http://www.djo.eg.net/text.asp?2020/21/1/6/279721
| Introduction|| |
The tear film is a thin layer that covers the outer surface of the eye, 3 µm thick and 3 µl in volume. It is formed of three layers: superficial thin lipid layer, a middle thick aqueous layer, and an innermost hydrophilic mucin layer. A dysfunction of any of these layers can result in dry eye disease .
Clinical diagnosis of dry eye syndrome reveals a spectrum of clinical symptoms ranging from mild irritation symptoms with minimal ocular surface disease to severe and disabling irritation . So, clinical diagnostic tests were essential for an objective quantitative assessment of tear film status. Schirmer’s test (ST) is the most commonly used technique for assessing tear secretion. It is based on estimation of the rate of tear formation and volume; this allows to quantitatively assess the severity of aqueous deficiency . Tear breakup time (TBUT) is a measure of the length of time the eye can be kept open before the tear film ruptures spontaneously (dry spot formation), assessing the integrity of the mucin layer .
It is known that the comprehension of normal values of the tests used in the diagnosis of any disease is essential in making an accurate diagnosis, taking into consideration that these test values are under multiple variables that definitely will differ from one country to another. So, the aim of the present study was to identify the normative data of ST and TBUT in a sample of Egyptians and the variables that may significantly affect these values.
| Patients and methods|| |
The current study is a cross-sectional observational hospital-based study that included 300 eyes of 150 Egyptian participants. All participants were free of dry eye symptoms, which were determined by the ocular surface disease index (OSDI) questionnaire , as shown in [Figure 1]. Participants were randomly recruited from the relatives of patients admitted in the Ophthalmology Department in Kasr-Alaini Hospital and from participants coming for glasses prescription in the Outpatient Clinic of Kasr-Alaini Hospital in the period from February 2016 till August 2016.
Participants enrolled in the study were divided into three age groups:
- Group A: 20–40 years old.
- Group B: more than 40–60 years old.
- Group C: above 60 years old.
Each group was subdivided into males and females.
Exclusion criteria included history of any systemic disease known to affect the lacrimal function, for example, rheumatoid arthritis; history of any ocular surface disease or any chronic ocular disease; history of previous ocular surgery or trauma; history of persistent eye drops use, for example, anti-glaucoma medications; and history of contact lens wear.
All participants enrolled in the study were subjected to full personal history, including name, sex, age, residency, occupation, and special habits such as using computers for long hours, and full present and past history to detect exclusion criteria. All participants enrolled in the study had a score in the OSDI questionnaire of less than 10 out of 100.
All participants got full ophthalmological examination of both eyes (done after finishing the tests of the study). External ocular examination was done. The lids were examined for the presence of any anatomical abnormalities interfering with normal spread of the tear film. Slit lamp biomicroscopy was performed, and the presence of mucus strands in the tear film and corneal filaments was noted. Lid margins were examined for irregularity or thickening. Meibomian orifices were examined. The tarsal conjunctiva was examined for the presence of papillae.
All participants signed a written informed consent to participate in the study and for publication of data before enrollment in the study. The study was performed according to the Declaration of Helsinki and was approved by the Institutional Review Board and Ethical Committee of Cairo University. All patients received a thorough explanation of the study design and aims.
The test was described for the participant first. A standard Whatman number 41 filter paper was placed in the lower fornix without any topical anesthesia. After 5 min, the participant was asked to open his eyes and the filter paper was removed, and the wetting was recorded from the grading scale on the paper. The usual grading for the ST is that wetting of 15 mm in 5 min is considered suspicious and wetting of 10 mm or less is considered positive for the existence of keratoconjunctivitis sicca. However, in this study, the decision for being normal and the inclusion criteria depended on the OSDI questionnaire and signs of dry eye. The participant was then given a rest period before starting the next test.
Tear breakup time
The test was described for the participant first. A fluorescein strip wetted with saline was placed in his/her lower fornix and the participant closed his/her eyes. The strip was then removed. The participant was then asked to blink many times to help distribute the fluorescein and then to stare directly in front of him/her without blinking, closing his/her eyelids or moving his/her eyes. The cornea of the participant was examined by the cobalt blue filter of the slit lamp for any black spots in the greenly stained tear film. The time from the last blink till the appearance of the black spot was recorded. The test was repeated twice again, and the average of the three tests was recorded. The black spots should appear randomly and not in a fixed site.
Data were statistically described in terms of mean±SD, range or frequencies (number of cases), and percentages when appropriate. Comparisons between groups were done using unpaired t test when comparing two groups and analysis of variance with multiple comparisons post hoc test when comparing more than two groups. Correlations between quantitative variables were done using Pearson correlation coefficient. Multivariate linear regression analysis was done to predict ST and TBUT using age, sex, residence rank, and occupation rank. P values less than 0.05 were considered statistically significant.
| Results|| |
The 150 participants, in the present study, included 62 (41.3%) males and 88 (58.7%) females. The mean age of the participants was 37.38±12.77 years, ranging from 20 to 79 years.
Regarding residency, the study included 102 (68%) urban participants and 48 (32%) rural participants.
Regarding occupation, the participants were divided into different ranks: executive white collar (professionals, e.g. doctors and engineers), ordinary white collar (subprofessionals, e.g. nurses), green collar (e.g. farmers), pink collar (office-related work), skilled blue collar (technicians), unskilled blue collar (workers), and no collar. Executive white collar included 29 (19.3%) participants, ordinary white collar included 10 (6.7%) participants, green collar included 13 (8.7%) participants, pink collar included 23 (15.3%) participants, skilled blue collar included 10 (6.7%) participants, unskilled blue collar included 16 (10.7%) participants, and no collar included 49 (32.7%) participants who were either housewives or retired participants. The participants were also divided according to occupation into indoor and outdoor occupations. The indoor occupations included 111 (74%) participants, and the outdoor occupations included 39 (26%) participants.
The mean ST for all participants was 21.9±9.13 mm, ranging from 2 to 30 mm. The fifth percentile included participants with ST less than 5 mm. The mean ST for different age groups was 21.86±8.9 mm for participants 20–40 years old, 20±9.58 mm for participants 40–60 years old, and 19.56±9.07 mm for participants above 60 years old ([Figure 2]).
|Figure 2 Number of participants for different values of Schirmer’s test.|
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The mean ST for males was 22.55±8.7 mm and for females was 20.23±9.33 mm. The mean ST for urban participants was 21.76±8.9 mm and for rural participants was 20.18±9.51 mm. The mean ST for different occupations was 23.28±8.69 mm for unskilled blue collar, 20.55±10.52 mm for skilled blue collar, 22.02±8.01 mm for pink collar, 17.04±10.44 mm for green collar, 22.2±9.85 mm for ordinary white collar, 23.88±7.39 mm for executive white collar, and 19.55±9.4 mm for no collar. The mean ST for the indoor occupations was 21.43±8.80 mm and for the outdoor occupations was 20.50±10.02 mm.
Studying the correlation between ST and age showed a negative relation with a correlation coefficient (r) of −0.169, which was statistically significant (P=0.003). This means that the value of ST decreases with advancing age ([Figure 3]).
In addition, the association between ST and sex was statistically significant (P=0.03). The mean ST was less in females than in males.
The association between ST and occupation was also statistically significant (P=0.013). The mean ST was least in green collar and highest in the executive white collar.
The association between ST and the indoor/outdoor occupation classification showed that the ST was less in participants working outdoor than those working indoor. However, the relation was not statistically significant.
The ST was less in the rural group than in the urban group. However, the difference was statistically insignificant (P=0.169).
Studying linear regression for ST with age, sex, occupation, and residency showed that ST was mostly affected by age, with a P value of 0.004 and a standardized coefficient of 16%. The sex comes next, with a P value of 0.023 and a standardized coefficient of 13%. However, the occupation and residency showed no statistically significant effect in the regression model.
The mean TBUT for all participants was 16.04±4.99 s, ranging from 3 to 20 s. The fifth percentile included participants with TBUT less than 5 s ([Figure 4]). The mean TBUT for different age groups was 15.94±5 s for participants 20–40 years old, 16.73±4.49 s for participants 40–60 years old, and 13.44±6.62 s for participants above 60 years old. The mean TBUT for males was 16.56±4.63 s and for females was 15.67±5.2 s. The mean TBUT for urban participants was 15.47±5.27 s and for rural participants was 17.36±4.07 s. The mean TBUT for different occupations was 17.12±4.86 s for unskilled blue collar, 16.9±4.87 s for skilled blue collar, 15.09±5.59 s for pink collar, 17.31±3.73 s for green collar, 15.95±4.88 s for ordinary white collar, 15.38±5.04 s for executive white collar, and 16.02±5.01 s for no collar. The mean TBUT for the indoor occupations was 15.65±5.11 s and for the outdoor occupations was 17.13±4.46 s.
|Figure 4 Number of participants for different values of tear breakup time.|
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Studying the correlation between TBUT and age showed a negative relation, with correlation coefficient (r) of −0.03, which was statistically insignificant (P=0.60, [Figure 5]). However, in the age group above 60 years, the correlation was statistically significant (r=−0.56 and P=0.024).
The association between TBUT and sex was statistically insignificant (P=0.122).
The association between TBUT and occupation was also statistically insignificant (P=0.372). However, the association between TBUT and the indoor/outdoor occupation was statistically significant (P=0.017). The mean TBUT for participants who work indoor was less than those who work outdoor.
The association between TBUT and residency was statistically significant (P=0.001). The mean TBUT for urban participants was less than rural participants.
Studying linear regression for TBUT with age, sex, occupation, and residency showed that TBUT was mostly affected by residency, with a P value of 0.009 and a standardized coefficient of 15%. However, the age, occupation, and sex showed no statistically significant effect in the regression model.
Studying the correlation between ST and TBUT showed a positive relation, with r=0.292, which was statistically significant (P<0.001). The correlation between them was also statistically significant in the males and females (P=0.035 and <0.001, respectively). It was statistically significant in the urban participants (P<0.001) but not significant in the rural subgroup. It was statistically significant in the following occupational subgroups: executive white collar (P=0.009), ordinary white collar (P=0.012), pink collar (P=0.001), and no collar (P=0.001, [Figure 6]).
| Discussion|| |
Dry eye is a common disorder seen in ophthalmic practice, presenting with myriad of symptoms and signs that the clinician too often overlooks, resulting in under-diagnosis of the condition. In an Egyptian study, the prevalence of dry eye disease in southern Egypt was studied. Of 3128 patients who presented to the Ophthalmology Outpatient Clinic of Sohag University Hospital, Egypt, between January 2011 and August 2013, 713 (22.8%) patients were found to have dry eye .
The aim of the present study was to identify the normative data of ST and TBUT in a sample of Egyptians, which is to our knowledge not standardized by any previous study.
The mean ST for the Egyptian population sample was 21.19±9.13 mm. It was mostly affected by age where the value decreases with advancing age. It was also affected by sex where the value in females was 2 mm less than in males.
The mean tear film breakup time for the Egyptian population sample was 16.04±4.99 s. It was mostly affected by residency, with the value in urban population being less than in the rural population by 2 s.
This population-based epidemiologic data have been reported in different studies in different areas of the world. The mean ST and TBUT values are shown in [Figure 7].
|Figure 7 Mean Schirmer’s test and tear breakup time values of different studies.|
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An Indian study by Mishra and colleagues, assessed the tear secretion in healthy Indian volunteers by performing ST and TBUT. The mean ST was 19.83±11.47 mm and the mean TBUT was 17.52±11.61 s. The mean ST in male participants was 18.78±12.08 mm, whereas in female participants, it was 20.88±10.86 mm. However, the mean TBUT in males was 18.91±12.57 s and in females was 16.22±10.65 s. They found that the correlation of age with TBUT and ST was statistically significant, showing a negative relation. However, the correlation of sex with TBUT and ST was not statistically significant .
In Iran, in 2015, a study evaluated the tear film stability by the Javal-Shiotz keratometer and by the conventional TBUT. The mean TBUT for the sample was 15.74±8.9 s. The correlation of the tear film stability with age and sex was statistically insignificant, which is supportive of the current study .
A Chinese study, in 2014, studied the effect of aging on different tear function tests. A total of 50 normal volunteers ranging from 17 to 74 years old underwent ST and TBUT. The mean ST for all participants was 14.7±5.7 mm; for male participants, it was 16.7±7.1 mm, and for female participants, it was 13.4±4.2 mm. The mean TBUT for all participants was 9±3 s; for male participants, it was 9.5±3.7 s, and for female participants, it was 8.8±2.6 s. The correlation of the tear function tests with age showed no significant relation with TBUT, which supports the present study. In addition, similar to the current study, they found statistically significant negative correlation with ST (r=−0.328). Moreover, correlating sex with tear film stability showed a statistically insignificant relation, which supports our study . The tear function test results, in the Chinese people, are much lower than in the Egyptians, which may be related to being two different races and to the difference in the climate between both countries.
Patel in 1995 studied the TBUT in different ethnic and racial groups and obtained different results. Their study included 100 participants: 25 Chinese, 25 Africans, 25 Indians, and 25 whites. The mean TBUT for the Chinese group was 9.8±3.9 s, Indian group was 16.4±6.9 s, African group was 11.8±5.9 s, and white group was 19.9±8.3 s. The correlation between the TBUT and the different groups was statistically significant . Our population sample had TBUT mean near to the Indian group.
A Saudi study, in 2014, showed that the mean TBUT for all participants was 12.25±1.65 s. The lower TBUT of the Saudi study compared with the current study results can be explained by the difference in climate between the two countries, where the weather in Saudi Arabia is much hotter with higher humidity .
In Nepal, in 2013, ST with and without anesthesia and TBUT were performed for all participants. The mean ST without anesthesia for the normal participants was 20.22±8.89 mm, whereas with anesthesia, it was 13.25±6.64 mm. The mean TBUT for the normal participants was 16.52±5.65 s. The correlations of the tear function tests with the sex and occupation in this study were statistically insignificant unlike our study . The values of tear function tests of this study were surprisingly near to our study, which can be explained by the similar weather in both countries.
The mean ST in a Turkish study was 14.18±6.39 mm for male participants, 13.77±6.84 mm for female participants, and 13.97±6.61 mm for the whole sample. The mean TBUT was 23.5±6.25 s for male participants, 27±5.7 s for female participants, and 25.25±5.97 s for the whole sample. The ST appeared to decrease with age, although this was not statistically significant. The TBUT appeared to show a negative relation with age .
In Japan, in 2006, the mean value of ST, performed without anesthesia, was 14.7±9.7 mm. The mean value for TBUT was 6.2±3.3 s. The correlation between ST and age was statistically significant (P<0.0001), with ST decreasing with advancing age. This supports our study. However, in contrary to our study, the correlation of TBUT with age was statistically significant (P=0.03) .
Kasr-Alaini Hospital is a tertiary center with referrals from all over Egypt, and this allowed us to enroll participants with different residencies including urban and rural areas. This also allowed us to include participants with different occupations. We performed both ST and TBUT, which allowed us to have a picture of the tear secretion and stability in our sample and allowed us to get relation between them.
The limitations of the present study include unequal age distribution of the population sample, short time of the study, and being a one-center study (Kasr-Alaini Hospital).
From this study, the authors have got a picture of the normative data of ST and TBUT and the effect of different variables on both tests.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]