|Year : 2018 | Volume
| Issue : 1 | Page : 9-13
Comparative study between smokers and nonsmokers regarding dry eye
Hosam Eldine Mohamed Khalil1, Safaa Awadallah Aboud MD 1, Mostafa Amer Azzab2
1 Department of Ophthalmology, Beni Suef University, Beni Suef, Egypt
2 Department of Ophthalmology, El Nour Eye Hospital, Giza, Egypt
|Date of Submission||07-Dec-2016|
|Date of Acceptance||10-Apr-2017|
|Date of Web Publication||1-Feb-2018|
Safaa Awadallah Aboud
23 Namek Street, Mold El Naby Square, Beni Suef 62511
Source of Support: None, Conflict of Interest: None
The purpose of this study was to evaluate the relationship between smoking and dry eye in the adult population.
Patients and methods
A total of 500 male patients, 250 smokers and 250 nonsmokers, were recruited for this study in the period between May 2015 and April 2016. In addition to history taking and general examination, all participants were asked about eye irritation symptoms and were subjected to slit lamp and fundus examination. Schirmer 2 test, using topical anesthesia, tear break-up time (TBUT), and rose bengal staining were done for all study participants.
There was no statistically significant difference between the age of patients in both groups. The mean age of smokers was 41.44±7.55 years, whereas in nonsmokers it was 39.97±7.59 years. Schirmer 2 test values were significantly lower in smokers compared with nonsmokers (P=0.017). In smokers, the mean value of Schirmer 2 test was 13.91±6.81 mm, whereas in nonsmokers it was 16.58±7.41 mm. TBUT values of the smokers were significantly lower in smokers than in nonsmokers (P=0.035). It averaged 11.9±5.8 s in smokers and 14.9±5.5 s in nonsmokers. The rose bengal staining scores did not differ between the two groups (P=0.467). Additionally, a linear negative correlation was detected between smoking index of smokers and their Schirmer 2 test and TBUT values. The eye irritation indices of the smokers were statistically higher than those of the nonsmokers (P=0.0007).
The findings of this study suggest that smoking affects the tear film secretion and stability. In addition, it causes eye irritation symptoms, and so smokers are more likely to have dry eyes and severity of dry eye is more in smokers than in nonsmokers.
Keywords: comparison, dry eye, eye irritation index, rose bengal staining, Schirmer 2, smoking, tear break-up time
|How to cite this article:|
Khalil HM, Aboud SA, Azzab MA. Comparative study between smokers and nonsmokers regarding dry eye. Delta J Ophthalmol 2018;19:9-13
|How to cite this URL:|
Khalil HM, Aboud SA, Azzab MA. Comparative study between smokers and nonsmokers regarding dry eye. Delta J Ophthalmol [serial online] 2018 [cited 2018 Nov 18];19:9-13. Available from: http://www.djo.eg.net/text.asp?2018/19/1/9/224560
| Introduction|| |
Tobacco smoke contains more than 4000 toxic compounds, and is considered one of the top five risk factors of mortality with more than five million deaths a year ,. Upon exposure to ocular tissues, these compounds are eventually poisonous and affect the eye through ischemic and oxidative mechanisms . Many ophthalmologic disorders are thought to be associated with tobacco smoking such as cataract, age-related macular degeneration, retinal ischemia, anterior ischemic optic neuropathy, and tobacco–alcohol amblyopia .
The tear film overlies the ocular surface, which comprises the corneal and conjunctival epithelia, and provides the interface between these epithelia and the external environment. The tear film is essential for the health and protection of the corneal and conjunctival tissues and for clear vision, as the tear film is the first refractive surface of the eye .
Being very sensitive to chemicals and gases resulting from smoking, the conjunctival mucosa shows redness, excessive lacrimation, and discomfort as a consequence of conjunctival free nerve endings stimulation, which in turn increases the possible risk of dry eye ,.
Although tobacco smoke is thought to cause conjunctival irritation and dryness of the eye, the published studies are inconsistent and did not include sufficient study samples. The aim of the current study was to evaluate the relationship between smoking and dry eye in the adult population.
| Patients and methods|| |
This study was conducted on 500 patients in the period between May 2015 and April 2016 at the Ophthalmology Outpatient Clinic, Beni Suef University Hospital. The patients were divided into two groups:
The smoker group comprised 250 male patients aged between 30 and 50 years (mean age: 41.44±7.55 years) who were smoking cigarettes for at least 1 year before the time of study enrollment.
The nonsmoker group comprised 250 male patients aged between 30 and 50 years (mean age: 39.97±7.59 years) who had never smoked and did not have smokers in their first-degree relatives to rule out the effect of passive smoking.
Any patient with systemic or ocular disease that may affect the secretion or distribution of tears on the surface of the globe was excluded from the study. The exclusion criteria were as follows:
- Positive history of drug abuse, use of contact lens, and ocular surgery.
- Use of eye drops for long durations.
- All patients with abnormalities in the cornea or conjunctiva or lid.
- Patients with atopy or allergic diseases.
- Sjogren’s syndrome.
- Diabetic patients and patients with autoimmune disorders to avoid the secondary ocular effect.
All study participants were subjected to detailed history taking, slit lamp examination, and fundus examination. All patients were asked about smoking history, and the smoking index was calculated by multiplying the number of cigarettes smoked per day by the number of years the person has smoked. Medical and surgical history and history of drug intake were also inquired about.
The participants were asked about the presence of the following ocular symptoms: redness, irritation, lacrimation, dryness, tiredness, and itching. Then, they were asked about the frequency of such symptoms and, on the basis of their answers, they were divided into three groups according to Frank and Skov :
- Those with eye irritation occurring less than once a month.
- Those with eye irritation occurring once a week to once a month.
- Those with eye irritation occurring several times a week .
Patients who fulfilled the eligibility criteria underwent a number of tests in the following order: Schirmer 2 test, tear break-up time (TBUT), and rose bengal (RB) staining. An interval of 40 min was left between tests to minimize the interaction of these tests. All tests were performed by the same ophthalmologist.
RB is a vital stain that reveals dead or devitalized cells on the ocular surface. A technique for quantitative assessment of RB staining in ocular surface disorders was described .
In this study, Schirmer 2 test, TBUT, RB staining scores, eye irritation index, and eye irritation symptom values were evaluated.
The study was approved by the Ethical Committee of the Scientific Research, Faculty of Medicine, Beni Suef University. Patients were given full explanations about the purpose of the study and its consequences, with confirmation regarding the confidentiality of data. Informed consent was signed by all participants.
Data were analyzed using the software statistical package for the social science (SPSS, version 20; SPSS Inc., Chicago, Illinois, USA), and then processed and tabulated. Frequency distribution with its percentage and descriptive statistics with mean±SD were calculated. χ2, t test, and correlations were done whenever needed. P values of less than 0.05 were considered significant.
| Results|| |
Of the 500 male patients participating in the study, 250 patients were current smokers and 250 had never smoked. The age of the patients in both groups ranged between 30 and 50 years, and the mean age of smokers was 41.44±7.55 years, whereas that of nonsmokers was 39.97±7.59 years, with no statistically significant difference between the two groups (P=0.085) ([Table 1] and [Figure 1]). Schirmer 2 test values were significantly lower in smokers compared with nonsmokers (P=0.017); its mean was 13.91± 6.81 mm in smokers and 16.58±7.41 mm in nonsmokers ([Table 1] and [Figure 2]). TBUT values of the smokers were significantly lower than those of nonsmokers (P=0.035). In smokers, the mean TBUT was 11.9±5.8 s, whereas in nonsmokers it was 14.9±5.5 s ([Table 1] and [Figure 3]). The RB staining scores did not differ between the two groups (P=0. 467, [Table 2] and [Figure 4]).
|Table 1: The mean±SD of age, tear break-up time, and Schirmer 2 test in smokers and nonsmokers|
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|Table 2: Rose bengal staining test scoring in smokers and nonsmokers (P=0.467)|
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|Figure 2: Comparison between smokers and nonsmokers regarding Schirmer 2 test (mm/5 min).|
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|Figure 3: Comparison between smokers and nonsmokers regarding tear break-up time (TBUT) (s).|
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|Figure 4: Comparison between smokers and nonsmokers regarding rose bengal (RB) staining test score.|
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In addition, the eye irritation indices of the smoker group were statistically higher than those of the nonsmoker group (P=0.0007, [Table 3] and [Figure 5]).
|Table 3: Distribution of the smokers and nonsmokers according to eye irritation index (P=0.0007)*|
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|Figure 5: Comparison between smokers and nonsmokers regarding eye irradiation index questionnaire.|
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There was a statistically linear negative correlation between the smoking index on one hand and Schirmer 2 test and TBUT values on the other hand; the higher the smoking index, the lower the Schirmer 2 and TBUT values ([Figure 6] and [Figure 7]).
|Figure 6: Scatter plot of negative correlation between smoking index and Schirmer 2 value in smokers.|
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|Figure 7: Scatter plot of negative correlation between tear break-up time (TBUT) (s) and smoking index.|
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| Discussion|| |
Tobacco smoking is a known risk factor for many systemic and ocular diseases. However, there have been few studies linking smoking to dry eye, and the findings evolving from these studies are contradictory .
In the present study, it was clear that Schirmer 2 test and TBUT values in smokers were significantly lower than those of nonsmokers. The RB staining scores did not differ between the two groups. In addition, the eye irritation indices of the smokers were statistically higher than those of the nonsmokers. The study detected a linear negative correlation between the smoking index and Schirmer 2 test and TBUT values.
In general, two main theories can explain the current findings. The first theory is the ischemic theory based on the fact that toxins associated with smoking decrease blood flow or contribute to clot formation within ocular capillaries, thus cutting off nutrients that are essential for eye cell physiology. The second theory is that the lack of antioxidants such as free radicals, aldehydes, peroxides, epoxides, nitrogen oxides, and peroxyl radicals emerging from peroxidation can lead to a disturbance in the normal functionality of the ocular tissue .
Besides, tobacco smoking may damage ocular surface epithelium because of the direct contact between airborne particles coming from smoke and ocular surface. Yoon et al . reported a high amount of squamous metaplasia in the conjunctival surface epithelium in smokers. The authors justified their results by the absence of growth factors required for epithelial differentiation because of toxic irritation by the chemical compounds .
Consistent with the findings of the present study, Satici et al.  found that there was a decreased TBUT and tear lysozyme concentration, and increased Schirmer 1-test values, squamous metaplasia scores, eye irritation scores, and eye irritation indices, in chronic smokers as compared with the control group. In addition, there were no statistically significant differences in goblet cell counts or RB staining scores . Yoon et al.  concluded that TBUT, basal tear secretion, and corneal sensitivity were negatively correlated with both smoking and smoking index. Recently, Acar et al.  found that smoking behavior affected the dry eye parameters negatively. Matsumoto et al.  found that Schirmer test results were lower in smokers compared with nonsmokers. Altinors et al.  found that the mean Schirmer test value in smokers was significantly lower than that of nonsmokers. El-Shazly et al.  suggested that passive smoking would be a risk factor for dryness of eyes in children. Multiregression analysis of this study showed that the smoking index was the most important determinant of eye dryness in children . Uchino et al.  concluded that tobacco smoking might decrease tear secretion and goblet cell density in the conjunctiva of office workers. The authors proposed that tobacco smoking might lead to a decrease in the number of conjunctival goblet cells because of the associated inflammatory conditions .Unlike the present study, Thomas et al.  did not find any statistically significant difference between smokers and nonsmokers regarding Schirmer 2 test values. However, the authors found significant differences between smokers and nonsmokers regarding TBUT . Gabela Merino et al.  reported that smoking did not seem to affect tear meniscus, Schirmer 1, TBUT, slit lamp examination, and fluorescein staining in hydrogel contact lens wearers. Lee et al. , who conducted their study on patients with dry eye, did not find any relation between severity of dry eye and smoking.
However, few limitations of the current study should be taken into consideration. Only smoking men were included and the effect of passive smoking was not investigated. In conclusion, smoking is a risk factor for dryness of the eye based on Schirmer 2 test, TBUT, and the eye irritation indices. In addition, the severity of dry eye is more in smokers than in nonsmokers.
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]
[Table 1], [Table 2], [Table 3]