Original Article
Frequency and Risk Factors of Dry Eye
Disease in Pakistani Population, A Hospital Based Study
Abdullah
Ayub, Faryal Muhammad Akhtar, Najeeha Saleem, Muhammad Hassaan Ali, Muhammad
Hammad Ayub, Nadeem Hafeez Butt
Pak J Ophthalmol 2017, Vol. 33, No. 4
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See
end of article for authors
affiliations …..……………………….. Correspondence
to: Muhammad Hassaan Ali Department of Ophthalmology, Jinnah Hospital,
Lahore Email: mhassaanali@hotmail.com |
Purpose: To determine prevalence and risk factors of dry eye
in hospital based Pakistani population.
Study Design: Cross-sectional study. Place and Duration of Study: Department of Ophthalmology, Jinnah Hospital,
Lahore. From April 2016 to June 2016. Materials and Methods: Three hundred cases
above 18 years of age who presented to out-patient department with various
ophthalmic complaints were enrolled in the study. Patients with acute
inflammatory conditions, acute infections, gross corneal or conjunctival
diseases, contact lens wearers and those who had undergone any form ocular
surgery within the last 6 months were excluded from the study. After taking
detailed history, a pre-designed questionnaire was administered to the
patients that inquired about various symptoms of dry eyes followed by a
detailed ophthalmic assessment and measurement of tear film breakup time
(TBUT) using fluorescein dye. Patients exhibiting TBUT < 10 seconds were labeled
as dry eye sufferers.
Results: There were 300 participants enrolled in
the study with mean age 46.8 ± 8.3 years. 54.3% were female patients in the
study. The prevalence of dry eye was found to be 18.7%. Patients aged more
than 70 years showed significantly higher prevalence of dry eyes (p = 0.006). There were 18.9%
hypermetropes, 16.2% myopes and 15.2% emmetropes suffering from dry eyes. Multivariate
regression analysis showed that outdoor workers, people working in air
conditioners, housewives, diabetics, smokers, people exposed to excessive
sunlight, wind, temperature, and patients suffering from meibomian gland
dysfunction were at higher risk of developing dry eye.
Conclusion: Dry eye is associated with increasing age,
female gender, outdoor occupations, smoking, diabetes, meibomian gland
dysfunction and refractive errors.
Key
Words: Dry eye, Frequency, Diabetes, Risk Factors. |
Dry eye is caused by
abnormalities in the tear film which consists of lipid, aqueous and mucous
layers from anterior to posteriorly1. The definition of dry eye
disease has been under continuous revisions in the recent past. The current diagnosis
and definition of dry eye disease is based on 3 criteria as given in International
Dry Eye Workshop (DEWS) guidelines 2007: 1) decreased tear production or increased tear
evaporation, 2) damage to the ocular surface, and 3) associated ocular
discomfort or visual disturbance2. Various researchers have labeled
dry eye as the most prevalent condition seen in ophthalmology clinics3.
Due to tear film instability, dry eye patients report varying degree of
stinging, burning, irritation, foreign body sensation, watering, fatigue, redness
and photophobia etc. in the affected eye. The symptomatology of dry eye may
even be seen in the absence of full triad of features
mentioned above that define dry eye disease.
Various studies have
reported prevalence of dry eyes from 10% to 70% depending on the type of patients/subjects,
diagnostic criteria and objective tear film tests used in the study3.
Many factors have been reported in literature that are associated with
dry eyes that include hot weather, windy air conditions, excessive sun exposure,
pollution, smoking, advancing age in females, menopause etc4.
Recently, a large prevalence of dry eye disease has been reported in computer
users due to decreased blink rate during performance of visual tasks with deep
concentration5,6.
We
conducted a literature on Google Scholar, PubMed, EMBASE and Cochrane library
to find out earlier researches on the subject from Pakistan. Only one study was
found in which Jehangir et al had shown presence of dry eye disease with
various other ocular pathologies7. We believe that climatic and
environmental conditions of Pakistan mandate similar studies. We conducted this
study with the objectives to determine prevalence and risk factors of dry eye
in hospital based Pakistani population.
The study was conducted in
Department of Ophthalmology of Jinnah Hospital, Lahore, a tertiary care
hospital, from April 2016 to June 2016, after taking approval from Ethical
Review Board/ Institutional Review Committee of Allama Iqbal Medical
College/Jinnah Hospital, Lahore. The study was conducted following the
principles of good clinical practice as laid down in Declaration of Helsinki.
Informed written consent was taken from all the study participants.
We evaluated 300 cases above
18 years of age who presented to our out-patient department with various
ophthalmic complaints. The patients were selected following consecutive
purposive sampling. Only those patients
were selected who consented to take part in the study. Patients with acute
inflammatory conditions, acute infections, gross corneal or conjunctival
diseases, contact lens wearers and those who had undergone any form of ocular
surgery within the last 6 months were excluded from the study.
Three researchers (AB, FA,
NS) recorded detailed ophthalmic and general history of the patients focusing
on main causations associated with dry eyes. Sun exposure raised outdoor
temperatures, smoking, exposure to air pollutants and drugs were especially
asked about. After detailed history, another researcher (MHnA) administered a
pre-designed questionnaire about symptoms of dry eye. The questionnaire was
administered in language of the patients and asked for socio-demographic data including
age, gender, occupation, residence; and symptoms of dry eyes including
recurrent watering, foreign body sensation (grittiness), itching, burning,
stinging, dryness, soreness, heaviness etc.
Subsequently, a consultant ophthalmologist (MHdA) performed
detailed ophthalmic examination of all the patients. During ocular examination,
special attention was paid to ocular surface abnormalities, diseases of the
eyelids, meibomian gland dysfunction, presence of any strands or filaments etc. Lastly, status of the precorneal tear film was
assessed using tear film break-up time (TBUT). The test was performed at room
temperature, keeping fans turned off after application of fluorescein dye in
the inferior fornix. The patient was asked to blink 4 – 5 times to allow even
distribution of fluorescein dye over the ocular surface. Finally, the patient
was asked not to blink any further and was examined on slit lamp biomicroscope
with cobalt blue filter. Time interval between last blink and appearance of
first area of discontinuation in the precorneal tear film was TBUT. Patients
exhibiting this interval to be less than ten seconds were labelled to be
suffering from dry eyes. If any patient reported usage of ocular lubricants,
his TBUT was measured after discontinuation of that medicine for at least 24
hours.
SPSS
version 20.0 (SPSS Inc., Chicago, Illinois, USA) was used to do data analyses
using 95% confidence intervals (CI). The likelihood ratio was used to calculate
the p-values using Pearson Chi-square tests with a p-value of less than
0.05 considered as statistically significant. Associations of environmental
risk factors with dry eye were assessed using regression analysis. The strength
of association of environmental factors with dry eyes was found out by
calculating odd ratio.The difference in the mean number of dry eye symptoms
between dry eyed and normal individuals was assessed using analysis of variance
test (ANOVA). A p-value < 0.05 was considered
statistically significant.
Three hundred patients
participated in the study with mean age 46.8 ± 8.3 years. There were 163
(54.3%) females and 137 (45.3%) males in the study. The detailed
socio-demographic characteristics of the patients are shown in Table 1. The
most common presenting complaint of the patients with dry eyes was blurring of
vision in 29 (51.8%) of the cases followed by recurrent watering and itching in
39.3% and 19.6% of the cases respectively (Table 2). The frequency of dry eye
was found to be 18.7% (56 cases) in our study population. Patients aged more
than 70 years showed significantly higher prevalence as compared with rest of
the groups in 40.0% of the cases (p =
0.006; 95% CI 1.346 – 5.780) (Table 3). A relative peak of dry eye prevalence
was noted in age group 31-40 years (20.3%). As compared to males (16.1%),
females showed significantly higher prevalence of dry eyes (26.4%) (p = 0.021; 95% CI 1.080 – 2.631). Menopausal
women showed higher prevalence than non-menopausal women 30.1% versus 21.5% respectively.
Though the prevalence of dry eye came out to be more in rural population
(20.6%) as compared with urban population (17.6%) (p = 0.611; 95% CI
0.552 – 1.392), this result was not statistically significant. A detailed analysis of prevalence of dry eye
according to age, gender and place of residence is presented in Table 3.
The most commonly affected
people with dry eye were farmers and laborers 13 (27.1%) followed by high
exposure individuals (4, 25.0%) that included professional computer users, professional
drivers, field salesmen, field workers, outdoor painters, mechanics and cooks
(Table 4). Odd’s ratios to show strength of associations of various
occupations, environmental factors, systemic illnesses and drugs with dry eye
as measured through multivariate regression analysis are shown in Table 5. Briefly,
outdoor workers, people working in air conditioners, housewives, diabetics,
smokers, people exposed to excessive sunlight, wind, temperature, and patients
suffering from meibomian gland dysfunction were at higher risk of developing
dry eye.
As part
of detailed ophthalmic examination, all patients underwent assessment of their
refractive status as well. 15.2% of emmetropes suffered from dry eyes while 16.2%
(16/105) myopes and 18.9% (22/116) hypermetropes were affected by this
condition. The mean number of ocular symptoms in dry eye patients was
significantly higher as compared to non-dry eye group: 6.8 ± 2.1 versus 3.4 ±
2.3 (p = 0.001; 95% CI 1.69- 2.86).
Table 1: Socio-demographic
characteristics of participants in the Study (n = 300).
|
|
Number of Subjects |
Percentage (%) |
|
Age Groups (years) |
||
|
21 – 30 |
70 |
23.4 |
|
31 –
40 |
59 |
19.7 |
|
41 –
50 |
62 |
20.6 |
|
51 –
60 |
55 |
18.3 |
|
61 –
70 |
34 |
11.3 |
|
Above
70 |
20 |
6.7 |
|
Gender
Distribution |
||
|
Male |
137 |
45.7 |
|
Female |
163 |
54.3 |
|
Residence |
||
|
Urban |
193 |
64.3 |
|
Rural |
107 |
35.7 |
|
Occupation |
||
|
Farmers
/ Labourers |
48 |
16.0 |
|
Others
with High Exposurea |
16 |
5.3 |
|
Indoor
Office Workers/Shopkeepers |
53 |
17.7 |
|
Others
with Low Exposureb |
55 |
18.3 |
|
Housewives/Students |
123 |
41.0 |
|
Factory
Workers |
5 |
1.7 |
|
a
Professional computer users, professional drivers, field salesmen, field
workers, outdoor painters, mechanics, cooks etc. b Doctors, teachers,
scientists, priests etc. |
||
Table 2: Presenting symptoms
of dry eye patients (n = 56).
|
Symptoms |
Number of
Participants |
Percentage (%) |
|
Blurred Vision |
29 |
51.8 |
|
Watering |
22 |
39.3 |
|
Itching |
11 |
19.6 |
|
Heaviness |
8 |
14.3 |
|
Burning |
7 |
12.5 |
|
Stickiness |
6 |
10.7 |
|
Dryness |
5 |
8.9 |
|
Grittiness |
4 |
7.1 |
|
Excessive Mucoid
discharge |
3 |
1.7 |
Table 3: Prevalence of dry
eyes according to age, gender and residence.
|
|
Number of Subjects |
Dry Eye Subjects |
Prevalence (%) |
p-value |
95% CI |
|
Age
Groups (years) |
|||||
|
21 – 30 |
70 |
10 |
14.3 |
0.110 |
0.381 – 1.118 |
|
31 – 40 |
59 |
12 |
20.3 |
0.502 |
0.671 – 1.898 |
|
41 – 50 |
62 |
10 |
16.1 |
0.182 |
0.471 – 1.394 |
|
51 – 60 |
55 |
9 |
16.4 |
0.990 |
0.485 – 1.620 |
|
61 – 70 |
34 |
7 |
20.5 |
0.054 |
0.551 – 2.121 |
|
Above 70 |
20 |
8 |
40.0 |
0.006 |
1.346 – 5.780 |
|
Gender
Distribution |
|||||
|
Male |
137 |
22 |
16.1 |
0.021 |
1.080 – 2.631 |
|
Female |
163 |
43 |
26.4 |
||
|
Residence |
|||||
|
Urban |
193 |
34 |
17.6 |
0.611 |
0.552 – 1.392 |
|
Rural |
107 |
22 |
20.6 |
||
Table 4: Prevalence of dry eye
in various occupational groups.
|
Occupation |
Number of Subjects |
Dry eye subjects |
Prevalence (%) |
p-value |
95% CI |
|
Farmers/ labourers |
48 |
13 |
27.1 |
0.059 |
0.980
– 2.863 |
|
Others with high exposure |
16 |
4 |
25.0 |
0.781 |
0.459
– 2.897 |
|
Housewives / students |
123 |
25 |
20.3 |
0.341 |
0.783
– 1.979 |
|
Factory workers |
5 |
1 |
20.0 |
0.714 |
0.088
– 6.183 |
|
Indoor office workers/ shopkeepers |
53 |
7 |
13.2 |
0.132 |
0.310
– 1.192 |
|
Others with low exposure |
55 |
7 |
12.7 |
0.079 |
0.287
– 1.098 |
Table 5: Multivariate
logistic regression analysis showing strength of associations of various
variables with dry eyes.
|
Variable |
P-Value |
Odd’s Ratio |
95% CI |
|
Occupation |
|||
|
a)
Farmers / Labourers/ High
Exposure Group |
0.059 |
2.091 |
0.980 – 2.863 |
|
b)
Indoor office workers/
shopkeepers |
0.132 |
1.868 |
0.310 – 1.192 |
|
c)
Other low exposure group |
0.079 |
1.010 |
0.287 – 1.098 |
|
d)
Housewives/ Students |
0.015 |
1.942 |
1.139 – 3.229 |
|
Meibomian Gland Dysfunction |
0.000 |
21.173 |
4.897 – 84.854 |
|
Diabetes |
0.001 |
2.315 |
1.371 – 3.810 |
|
Smoking |
0.139 |
1.44 |
0.452 – 1.249 |
|
Excessive Wind |
0.005 |
2.12 |
0.263 – 0.791 |
|
Sunlight/High Temperature |
0.012 |
1.94 |
0.309 – 0.872 |
|
Air pollution |
0.291 |
1.34 |
0.389 – 1.340 |
DISCUSSION
The main objectives of
this study to determine the prevalence and risk factors of dry eyes were
successfully met. Various studies have shown prevalence of dry eyes to vary from around 10% to 70%
depending on the diagnostic criteria used and cut-off values for various tear film assessment tests8.
Some studies performed tests only on those patients who had significant number
of positive complaints about dry eyes resulting in higher prevalence of dry
eyes9. Besides, some studies were carried out solely on patients
with rheumatoid arthritis or Sjogren’s syndrome who reported a high prevalence
of dry eyes10-13. Our prevalence (18.7%) results fall within
the aforementioned range and are in accordance with results from various other
studies.
Our results showed that the prevalence of dry eye
increased as the age of the patients increased showing a direct relationship
between age and dry eyes. This result was also consistent with many
other studies14-17. A relative peak of dry eye prevalence was found in
the age group 31-40 years as had earlier been observed by Hikichi et al18.
We believe this age group suffers most from the occupational hazards due to
maximum exposure to outdoor environmental risk factors leading to ocular dryness.
Countries like Pakistan with plenty of sun exposure can exhibit this phenomenon
to a greater extent. However, we recommend more studies in this regard to find
exact cause of this spike of prevalence of dry eyes in age group 31 – 40 years.
Like many
other studies19, our study also showed significantly higher
prevalence of dry eyes in females as compared to males (26.4% versus 16.1%; p = 0.021). The higher prevalence of dry
eyes in females implies that females seek medical attention earlier than males
for their dry eye symptoms. Besides, menopause causes decreased estrogen level
in females that lead to decreased tear film production in them20. We found out higher prevalence of dry eyes in post-menopausal
women as compared to pre-menopausal women (30.1% versus 21.5%) which might be
explained by the aforementioned normal physiological mechanism. Though our
patients showed a higher prevalence of dry eyes in post-menopausal women,
earlier studies have shown same prevalence of dry eyes in both pre-and post-menopausal
women14. People residing in rural areas showed higher prevalence of
dry eyes as compared to urban residents. But contrary to various other studies,
the difference was not statistically significant. The higher prevalence in
rural residents is thought to be the result of excessive exposure to sunlight
and high outdoor temperatures21.
People belonging to various occupations like
farmers/labourers, housewives; people with meibomian gland dysfunction,
diabetics, and people with excessive exposure to sunlight, wind, cigarette
smoking and air pollution were significantly related to dry eye. Khurana et al reported high prevalence of
dry eyes in farmers and labourers (32% and 28% respectively) most likely due to increased exposure to
hot temperatures and sunlight22,23. This necessitates urgent need to create
awareness among farmers and labourers to take safety measures during their
work. Many earlier studies have
shown smoking, diabetes and pollution to be risk factors for dry eyes24. Smokers who suffer from
dry eyes should be counseled about quitting or limiting smoking as a potential
therapy for their dry eyes by reducing direct irritant effect of smoking on
ocular surface.
Moss et al showed higher prevalence of dry eyes in patients
with refractive errors as compared to emmetropes25. Our study also
showed this relationship with refractive errors. These patients suffered more
than emmetropes from dry eyes. Comparing
emmetropes with refractive error group individuals, the prevalence of dry eyes
was higher in both corrected and uncorrected refractive error group. However,
subjects with their refractive errors corrected suffered less in this condition
as compared to those with uncorrected refractive error (16.3% versus 25.6%).
This difference in patients with corrected and uncorrected refractive error was
not statistically significant (p >
0.05). It has been proposed that persons with refractive errors rub their eyes
frequently leading to deposition of debris and infected particles in the
fornices leading to instability of the tear film. Our study also showed that
prevalence of dry eye was most in hypermetropes (18.9%) followed by myopes
(16.2%) and emmetropes (15.2%). Incorporating refractive errors in dry eye
researches has earlier been postulated in various studies25.
The
main limitation of our study was exclusion of patients with various corneal and
conjunctival pathologies which led to a relative apparent underestimation of
prevalence of dry eyes in our sample. Besides, participants using contact
lenses were also excluded who could have been a potential source of the
condition. Fluorescein dye was used to carry out tear film break up time which
itself was irritating and could cause reflex tearing. So, newer studies may use
non-invasive and non-contact techniques of measuring tear breakup time. Further
studies may be conducted to establish a uniform criterion for diagnosis and
more etiologic associations of dry eyes. This raises the need to gather more
data on the subject from our country.
Dry eye
is quite prevalent in our cohort of patients who were suffering from ocular
disease other than gross corneal and conjunctival pathologies. The study
reflects a major but underdiagnosed burden of the condition in our out-patient
departments. We conclude that dry eye is associated with increasing age, female
gender, outdoor occupations, smoking, diabetes, meibomian gland dysfunction and
refractive errors. The results should guide ophthalmic community in developing
more targeted and focused approaches towards management of this issue since dry
is not only an ocular disease but also a great burden on the economics of the
patient. Detailed history about symptoms of the condition and good clinical
examination with tear film break up time can help us properly diagnose and
manage this condition actively.
Author’s Affiliation
Dr.
Abdullah Ayub
MBBS
House Surgeon
Department
of Ophthalmology, Jinnah Hospital Lahore.
Dr.
Faryal Muhammad Akhter
MBBS
House Surgeon
Department
of Ophthalmology, Jinnah Hospital Lahore.
Dr.
Najeeha Saleem
MBBS
House Surgeon
Department
of Ophthalmology, Jinnah Hospital Lahore.
Dr.
Muhammad Hassaan Ali
BSc, MBBS
Postgraduate
Resident
Department of Ophthalmology, Jinnah Hospital, Lahore
Dr. Muhammad Hammad Ayub
MBBS,
FCPS
Associate
Professor
Department
of Ophthalmology, Jinnah Hospital Lahore.
Prof.
Nadeem Hafeez Butt
MBBS,
FCPS, FRSCEd,
FRCS
(Glas), MHPE
Department
of Ophthalmology, Jinnah Hospital Lahore.
Role of Authors
Dr. Abdullah Ayub
Conception,
Data collection, data entry, data analysis, article write up.
Dr. Faryal Muhammad Akhter
Data collection, data entry, data analysis,
article write up.
Dr. Najeeha Saleem
Data collection, data entry, data analysis,
article write up.
Dr.
Muhammad Hassaan Ali
Conception, Data collection, data analysis,
article write up.
Dr.
Muhammad Hammad Ayub
Data
collection, data analysis, Final critical review.
Prof.
Nadeem Hafeez Butt
Senior
author, conception, final critical review.
1.
Lienert JP, Tarko L, Uchino M, Christen WG,
Schaumberg DA.
Long-term Natural History of Dry Eye Disease from the Patient's Perspective.
Ophthalmology, 2016 Feb. 29; 123 (2): 425-33.
2.
Lemp MA, Foulks GN. The definition and classification of dry eye
disease. The Ocular Surface, 2007; 5 (2): 75-92.
3.
Ali MH, Javaid M, Jamal S, Butt NH. Femtosecond laser assisted cataract surgery,
beginning of a new era in cataract surgery. Oman J Ophthalmol. 2015 Sep; 8 (3):
141.
4.
Ranjan R, Shukla SK, Singh CV, Mishra BN, Sinha
S, Sharma BD.
Prevalence of Dry Eye and Its Association with Various Risk Factors in Rural
Setup of Western Uttar Pradesh in a Tertiary Care Hospital. Open Journal of
Preventive Medicine, 2016 Jan. 15; 6 (01): 57.
5.
Rosenfield M. Computer vision syndrome (aka digital eye
strain). Optometry, 2016; 17 (1): 1-0.
6.
Courtin R, Pereira B, Naughton G, Chamoux A,
Chiambaretta F, Lanhers C, Dutheil F. Prevalence of dry eye disease in visual display
terminal workers: a systematic review and meta-analysis. BMJ open, 2016 Jan. 1;
6 (1): e009675.
7.
Jehangir S. Dry eye syndrome in Pakistani community. J Pak
Med Assoc. 1990 Mar; 40: 66-7.
8.
Bakkar MM, Shihadeh WA, Haddad MF, Khader YS. Epidemiology of symptoms of dry eye disease
(DED) in Jordan: A cross-sectional non-clinical population-based study. Contact
Lens and Anterior Eye, 2016 Jun. 30; 39 (3): 197-202.
9.
Nowak MS, Smigielski J. The Prevalence and Risk Factors for Dry Eye
Disease among Older Adults in the City of Lodz, Poland. Open Journal of
Ophthalmology, 2016 Feb. 4; 6 (01): 1.
10.
Fostad IG, Eidet JR, Utheim TP, Ræder S, Lagali
NS, Messelt EB, Dartt DA. Dry Eye Disease Patients with Xerostomia Report Higher
Symptom Load and Have Poorer Meibum Expressibility. PloS one, 2016 May 5; 11 (5):
e0155214.
11.
Beckman KA, Luchs J, Milner MS. Making the diagnosis of Sjögren’s syndrome in
patients with dry eye. Clinical ophthalmology (Auckland, NZ), 2016; 10: 43.
12.
Ali MH, Ullah S, Javaid U, Javaid M, Jamal S,
Butt NH. Comparison
of characteristics of femtosecond laser-assisted anterior capsulotomy versus
manual continuous curvilinear capsulorrhexis: A meta-analysis of 5-year
results. J Pak Med Assoc. 2017; 67 (10): 1574–9.
13.
Atalay K, Ustun I, Cabuk KS, Kirgiz A, Karacan I,
Taskapili M. How
does rheumatoid arthritis affect corneal biomechanical properties? Int J Clin Exp
Med. 2016 Jan. 1; 9 (2): 4665-9.
14.
Javaid U, Ali MH, Jamal S, Butt NH. Pathophysiology, diagnosis, and management of
glaucoma associated with Sturge–Weber syndrome. Int Ophthalmol. Springer; 2017;
1–8.
15.
Jamal S, Ali MH, Ayub MH, Butt NH. Frequency and Grading of Diabetic Retinopathy in
Diabetic End Stage Renal Disease Patients. Pak J Ophthalmol. 2016; 32: 65.
16. Butt NH, Ayub MH, Ali MH. Challenges in the management of glaucoma in
developing countries. Taiwan J Ophthalmol. Elsevier; 2016; 6 (3): 119–22.
17. Bashir ZS, Ali MH, Anwar A, Ayub MH, Butt NH. Femto-LASIK: The recent innovation in laser
assisted refractive surgery. J Pak Med Assoc. 2017; 67 (4): 609.
18.
Hikichi T, Yoshida A, Fukui Y, Hamano T, Ri M,
Araki K, Horimoto K, Takamura E, Kitagawa K, Oyama M, Danjo Y. Prevalence of dry eye in Japanese eye centers.
Graefe's archive for clinical and experimental ophthalmology, 1995 Sep. 1; 233 (9):
555-8.
19.
Schaumberg DA, Uchino M, Christen WG, Semba RD,
Buring JE, Li JZ.
Patient reported differences in dry eye disease between men and women: impact,
management, and patient satisfaction. PloS one, 2013 Sep. 30; 8 (9): e76121.
20.
Agarwal R, Singh P, Rajpal T, Kumar R,
Raghuwanshi S, Ramnani V. Hospital based study of prevalence of dry eye in
post-menopausal women. Indian Journal of Clinical and Experimental Ophthalmology,
2016; 2 (1): 56-61.
21.
Ranjan R, Shukla SK, Singh CV, Mishra BN, Sinha
S, Sharma BD.
Prevalence of Dry Eye and Its Association with Various Risk Factors in Rural
Setup of Western Uttar Pradesh in a Tertiary Care Hospital. Open Journal of
Preventive Medicine, 2016 Jan. 15; 6 (01): 57.
22.
Khurana AK, Chaudhary R, Ahluwalia BK, Gupta S. Tear film profile in dry eye.
Actaophthalmologica. 1991 Feb. 1; 69 (1): 79-86.
23.
Lee JH, Lee W, Yoon JH, Seok H, Roh J, Won JU. Relationship between symptoms of dry eye syndrome
and occupational characteristics: the Korean National Health and Nutrition
Examination Survey 2010–2012. BMC ophthalmology, 2015 Oct. 29; 15 (1): 1.
24.
Sayin N, Kara N, Pekel G, Altinkaynak H. Effects of chronic smoking on central corneal
thickness, endothelial cell, and dry eye parameters. Cutaneous and ocular
toxicology, 2014 Sep. 1; 33 (3): 201-5.
25.
Moss SE, Klein R, Klein BE. Long-term incidence of dry eye in an older
population. Optometry & Vision Science, 2008 Aug. 1; 85 (8): 668-74.