|Year : 2016 | Volume
| Issue : 1 | Page : 32-40
Prevalence of dry eye disease in southern Egypt: a hospital-based outpatient clinic study
Engy M Mostafa
Ophthalmology Department, Sohag University, Sohag, Egypt
|Date of Submission||15-Sep-2015|
|Date of Acceptance||22-Dec-2015|
|Date of Web Publication||21-Oct-2016|
Engy M Mostafa
Ophthalmology Department, Sohag University, Sohag 82524
Source of Support: None, Conflict of Interest: None
The aim of this study was to determine the prevalence of dry eye disease (DED) in a tertiary ophthalmic outpatient hospital-based clinic in southern Egypt.
Patients and methods
A cross-sectional, observational, hospital-based study of 3128 patients was conducted at the Ophthalmology Outpatient Clinic of the Sohag University Hospital, Egypt, between January 2011 and August 2013. The participants comprised adult ophthalmic outpatients aged 18 years or older. DED was assessed subjectively with the Ocular Surface Disease Index (OSDI) questionnaire and objectively with Schirmer's test, tear film breakup time (TBUT), and conjunctival/corneal staining. An OSDI score of 22 or more with a TBUT of less than 10 s or Schirmer's test reading of less than 10 mm was considered diagnostic of definite DED. Descriptive and analytical statistics were performed. In all comparisons, P value less than 0.05 was considered to be statistically significant.
Dry eye disease prevalence was 22.8% in the 3128 patients. DED was significantly more prevalent in patients 45 years or older and in females. An OSDI score more than 22 was found in 55%, TBUT less than 10 s in 44.7%, and Schirmer's test score less than 10 mm in 39.3%. DED symptoms are significantly associated with meibomian gland dysfunction, previous refractive surgery, and diabetes. Definite DED was significantly associated with previous cataract surgery, ocular allergy, pterygium, and diabetes.
This is the first observational study of DED in southern Egypt on a large sample population. The prevalence of DED among ophthalmic outpatients at Sohag University Hospital, Egypt, was 22.8% depending on both symptoms and signs. Older age patients and females were more susceptible to DED. DED is an existing entity that can compound any eye condition causing incomplete recovery, and therefore high index of suspicion is greatly advised.
Keywords: dry eye disease, Egypt, Schirmer's test, tear film breakup time
|How to cite this article:|
Mostafa EM. Prevalence of dry eye disease in southern Egypt: a hospital-based outpatient clinic study. J Egypt Ophthalmol Soc 2016;109:32-40
|How to cite this URL:|
Mostafa EM. Prevalence of dry eye disease in southern Egypt: a hospital-based outpatient clinic study. J Egypt Ophthalmol Soc [serial online] 2016 [cited 2020 Oct 24];109:32-40. Available from: http://www.jeos.eg.net/text.asp?2016/109/1/32/192749
| Introduction|| |
The term ‘dry eye’ was first introduced by Andrew de Roetth in 1950 . The definition evolved until 1995, and dry eye disease (DED) was defined as a complex multifaceted group of medical and ocular diseases caused by decreased tear production and/or increased tear evaporation . In 2007, the International Dry Eye Workshop coined a new definition for dry eye as a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface .
Surveys over the last 20 years have estimated the prevalence of DED to be between 5% and more than 30% at various ages depending on which study is cited, how the disease is diagnosed, and which population is surveyed ,,.
The burden of DED to the patient is not negligible. Studies suggest that DED can have a considerable impact on visual function, daily activities, social and physical functioning, workplace productivity, and direct and indirect costs of the disease ,, with a substantial effect on sense of well-being that limits important daily activities and leads to a significantly reduced quality of life .
To the best of our knowledge, thus far, there are no studies conducted on the prevalence of dry eye in North Africa and Middle East depending on both signs and symptoms for diagnosis. In this study, an attempt was made to assess the magnitude of the problem of dry eyes in patients attending a general ophthalmology hospital eye clinic by administering a standard questionnaire and subjecting them to tests assessing the tear film profile.
| Patients and methods|| |
This prospective, cross-sectional, observational, hospital-based study examined 3128 consecutive patients presenting for eye examination to a general ophthalmology university hospital clinic in Sohag city, 500 km south of Cairo, Egypt, between January 2010 and August 2013. The mean number of patients attending the clinic each week is 750.
Inclusion criteria were as follows: patients above 18 years of age presenting with various ophthalmic complaints such as irritation, discomfort, dryness, presence of foreign body sensation, gritty sensation, burning sensation, and light sensitivity. Exclusion criteria were as follows: ocular infections, patients diagnosed with and on treatment for DED, lid deformity or abnormal lid movement disorder, refractive surgery within 1 year of the study visit, current pregnancy or lactation, abnormal nasolacrimal drainage, and punctual plug placement within 30 days of testing.
All patients underwent a through history check by an ophthalmologist. The active complaints were recorded.
A wide variety of questionnaires is available for the evaluation of DED, such as Ocular Surface Disease Index (OSDI), National Eye Institute Visual Function Questionnaire (NEIVFQ-25), and McMonnies Dry Eye Questionnaire . The OSDI questionnaire developed by the Outcomes Research Group at Allergan Inc. (Irvine, California, USA) is a useful tool for DED evaluation because of its simplicity and ease of use, which prompted us to use it after being translated into Arabic. It is a 12-item scoring survey, in which the patient rates his or her own ocular symptoms induced by environmental factors over the preceding 2–4 weeks. Answers are scored on a scale from 0 to 4; the total score can range from 0 to 100, with higher scores representing greater disability. The OSDI has an overall score and three subscale scores [ocular symptoms (three items), vision-related function (six items), and environmental triggers (three items)]. Each OSDI item is scored on a Likert-type scale ranging from 0 to 4 points, where 0 indicates none of the time and 4 indicates all of the time. On the basis of their OSDI scores, patients can be categorized as having a normal ocular surface (0–12 points) or as having mild (13–22 points), moderate (23–32 points), or severe (33–100 points) ocular surface disease. In a study comparing the OSDI with other dry eye questionnaires, the former was reported to be reliable (ranging from good to excellent as an overall instrument) and to have high validity . The OSDI questionnaire was administered by trained nurses (under supervision of the ophthalmologist) to help patients with no reading skills.
A complete ocular examination was carried out.
External ocular examination
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. The integrity of meibomian gland function was assessed for all patients according to the Foulks–Bron scoring system . Meibomian orifices were examined for pouting, presence of foam, secretion, and plugging. The tarsal conjunctiva was examined for the presence of papillae.
Objective testing included the following:
- Ocular surface staining by fluorescein dye was carried out. The Oxford schema (Bron)  was used to estimate the surface damage (staining of the cornea and conjunctiva).
- Tear film breakup time (TBUT) test was performed: 1% fluorescein dye was applied to the eye, and the average of three consecutive breakup times (using a stopwatch) was calculated. A breakup time of less than 10 s was considered abnormal.
- Finally, Schirmer's test with a local anesthetic (benoxinate hydrochloride 0.4%) was performed. After 2 min, Whatman's filter paper (5 mm × 35 mm, no. 41) was applied to the inferior conjunctival sac at the junction of the lateral one-third and medial two/thirds. The patient was instructed to look straight and was allowed to blink. After 5 min, the test strips were removed, and the amount of wetting was noted. Values less than 10 mm were considered to be abnormal.
The sequence of these tests was maintained so that each test did not affect the following. An OSDI score of 22 and above with a TBUT 10 s or less or Schirmer's test measurement 10 mm or less was considered diagnostic of definite DED. The classification of dry eye was carried out using the International Dry Eye Workshop severity grading system, which adopted and modified the Delphi scheme .
Written consent was obtained from all patients recruited to this study. The research protocol was approved by an institutional review board of Sohag University, Faculty of Medicine, and was in accordance with the Declaration of Helsinki.
The worse eye of each patient was used for the analysis. Statistical analyses were carried out using GraphPad Prism Software (version 6) (La Jolla, CA, USA). Analyses were performed according to age and sex. Tests for significant between-class differences utilized the χ2-test for categorical variables and the Student's t-test for continuous variables. Pearson's correlation coefficients of determination were calculated (r2) between each measurement type. A P value of less than 0.05 was considered statistically significant.
| Results|| |
In total, 3128 patients were recruited. The percentage of female patients was 58.3%. The mean patient age was 42±21 years. The age range was 18–75 years. Age and sex distribution of the participants are demonstrated in [Table 1].
[Table 2] demonstrates patients’ characteristic associations. The prevalence of ocular allergic symptoms and signs was 13.7%, which was significantly more prevalent in females (P = 0.015). The number of computer users was 739 (23.6%), with patients belonging mostly to the less than 45 years of age group. Male smokers constituted 25.9% of the population, whereas most of the females (14.7%) were passive smokers. Only eight patients had the diagnosis of rheumatoid arthritis.
The overall prevalence of dry eye was 22.8%. DED was significantly more prevalent in patients 45 years or older (with a prevalence of 71.7%) compared with those younger than 45 years of age (P = 0.001; [Table 3]). There were significant differences in overall dry eye prevalence between the sexes (P = 0.015). The percentage distribution according to the severity of DED is demonstrated in [Figure 1].
|Figure 1: Distribution of patients with dry eye disease according to the severity based on Classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007).|
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The prevalence of DED symptoms and signs varied as follows: significant symptoms (OSDI>22) in 49.6% [95% confidence interval (CI): 23.1–43.4], TBUT less than 10 s in 44.7% (95% CI: 42–59.1), Schirmer's score less than 10 mm in 39.3% (95% CI: 45.0–52.2), corneal fluorescein staining score greater than 1 in 30.6% (95% CI: 41.6–98.6), and meibomian gland dysfunction (MGD) was found in 18.5% (95% CI: 33.2–54) ([Figure 2]).
|Figure 2: Percentage of patients with MGD, corneal staining, Schirmer's test score less than 10 mm, TBUT less than 10 s, OSDI more than 22, and definite dry eye disease. MGD, meibomian gland dysfunction; OSDI, Ocular Surface Disease Index; TBUT, tear film breakup time.|
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Ocular Surface Disease Index questionnaire
The scores of items of the OSDI questionnaire are detailed in [Figure 3]. The percentage of patients who scored more than 22 was 49.6% with females constituting 55%. The mean±SD OSDI score was 31 ± 21 (range: 4–75). Among symptoms experienced, the most frequent symptoms with a score of 1 or more were eye discomfort in windy conditions (85%), sore painful eyes (60%), and gritty sensation (60%), whereas blurred vision was reported in 44% of patients. There was a statistically significant difference in OSDI scores between sexes (43 for females vs. 29 for males; P = 0.05). In addition, there was a statistically significant difference in OSDI scores between the younger age groups (18–45 years) and the older age groups (45–75 years) (P = 0.006). Of the 3128 patients, 24% reported the presence of one or more symptoms of dry eye often or always, whereas 21.5% reported the presence of symptoms sometimes, and 55.5% of them rarely had any symptoms. In contrast, MGD was significantly associated with OSDI scores more than 22 (P = 0.04), where 22.6% of symptomatic patients had MGD. This also applies to patients with previous refractive surgery and diabetic patients (P = 0.003 and 0.012, respectively). Dry eye symptoms were not significantly associated with other systemic diseases or medications.
|Figure 3: The distribution of scores of items of Ocular Surface Disease Index questionnaire.|
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Data are presented for the worse eye only as the agreement between the left eye and the right eye was very high for all clinical signs.
The mean±SD Schirmer's test score was 8.6 ± 8.7 mm (range: 3–16 mm). Comparison between age groups showed that patients aged 45 and above were found to have lower mean Schirmer's test scores (P = 0.001); however, there was no significant difference between sexes. The same applies to premenopausal and postmenopausal women. There was an inverse correlation between daily hours of computer use and Schirmer's test scores (r2 = −0.20, P = 0.04).
Tear film breakup time
TBUT less than 10 s was prevalent in 44.7% of cases, whereas only 50.9% of them had TBUT less than 5 s.
Prevalence of definite dry eye disease
Definite DED was found in 22.8% of outpatients who attended the eye clinic and met the inclusion criteria. Cataract extraction was associated with the highest percentage (57.1%) of definite DED among ocular pathologies followed by patients with ocular allergy (44.9%) and by those who had pterygia (40.9%). Among the systemic diseases, diabetes had the strongest association with definite DED (61.2%).
Correlation between subjective questionnaire and clinical tests
The Pearson correlation coefficient was 0.45 for Schirmer's test, 0.72 for breakup time, and 0.54 for corneal staining. Thus, a lower TBUT score has a better association with the presence of frequent dry eye symptoms compared with the other tests ([Table 4]).
|Table 4: Association between Ocular Surface Disease Index scores and positive dry eye tests|
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| Discussion|| |
Dry eye is a far too common disorder seen in ophthalmic practice, presenting with myriad of symptoms and signs that the clinician too often overlooks, resulting in underdiagnosis of the condition . In this study, an attempt was made to find out the magnitude of the problem in patients visiting Sohag University Hospital Outpatient Clinic, their sex, age distribution, and their common symptomatology.
Population-based epidemiologic data including symptoms and signs of dry eye in different age groups have been reported in different studies in different areas of the world as shown in [Table 5],[Table 6],[Table 7]. Nevertheless, the prevalence has varied with regard to their diagnostic criteria. Some studies have used only symptoms in their determination of dry eye prevalence ,,, whereas other studies have used symptoms in addition to biomicroscopic examination  and/or tests of ocular surface staining, tear film stability, and tear secretion ,. For the detection of dry eye conditions, neither history nor biomicroscopy alone was found to be adequate .
|Table 5: Prevalence studies of dry eye disease in Australia, Europe, and North America|
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The prevalence was lower when a combination of signs and symptoms were used as diagnostic criteria as in the Salisbury Eye Study , which matched this study's results. The prevalence was higher when symptomatic patients were examined for DED. Nita et al. found that out of the 237 patients who presented with standard symptoms of dry eye, 63% of patients were diagnosed positive for the disease. This also applies to the Shihpai Eye Study, which studied the Chinese population in Taiwan, and reported dry eye incidence of 62.5% in symptomatic patients . Out of the patients with OSDI score more than 22, 45.9% had DED.
In contrast to this study, the prevalence of abnormal dry eye tests in studies of white populations was lower. Possible explanations for these prevalence differences include race and ethnicity, participation rates, climate, environment, and pre-existing ocular conditions such as trachoma, which used to be endemic in this part of the world. As this study was conducted in southern Egypt, increased sunlight exposure and high ambient temperature may increase the frequency of dry eye symptoms . Kjaergaard et al.  reported that low ambient temperature and high relative humidity (RH) are associated with more tear film stability than low RH and high temperature, which applies to the geographic area where the study was conducted. Exposure to sun, dust, and wind exacerbate or precipitate DED .
A few reports could be found from Africa. Onwubiko et al. conducted a similar study in Nigeria on 402 adult patients with a DED criteria of OSDI score of 50 and above with a TBUT less than 5 s or Schirmer's test measurement less than 10 mm. They reported a DED prevalence of 19.2%. Given the fact that the sample size is far much larger and the DED diagnosis criteria are less restrictive, the prevalence is therefore slightly higher (22.8%).
A study on 200 outpatients in Egypt (Beni-Suef University Hospital)  showed prevalence of dry eye symptoms in 11.5% of patients and 2.5% with symptoms and an abnormal clinical test.
The published data regarding the relation between dry eye and age consistently show that dry eye is more common in the elderly ,,. In this study, an association with age was found in the analysis of dry eye tests as well as in the analysis of dry eye symptoms, which was not the case with Schaumberg et al..
The female patients showed higher prevalence of DED, which is similar to the results of other studies ,,, but different from the results of Schein et al. who reported no sex difference in prevalence. Hormonal studies suggest that sex hormones influence ocular surface conditions through their effects on tear secretions, meibomian gland function, and conjunctival goblet cell density . Androgen levels are higher in men than in women throughout life, and both sexes experience a decline in bioavailable androgens with aging , which explains both the higher prevalence in females as well as the elderly.
The poor correlation between symptoms and signs has been frequently reported in the literature ,. In this study, the strong association between positive TBUT and significant dry eye symptoms was found. The paradoxical relationship between symptoms and signs in DED can be explained either by the fact that symptoms can precede signs or that DED is a heterogeneous condition differing in etiology and pathophysiology, which varies from corneal nerve damage  to inflammatory processes , and different objective tests measure different aspects of tear physiology. There is also the fact that symptoms of DED are not specific to this particular disorder.
Dry eye disease is also associated with certain ocular conditions. The present study shared the results of the Beaver Dam Eye Study cohorts , which found that cataract extraction surgery was related to increased prevalence of dry eye. A reasonable explanation would be postoperative corneal desensitization. In the present study, lens surgery was an association in 34% of cases.
The association of dry eye and diabetes is still a debatable issue, where Moss et al. reported that the long-term incidence of DED was not significantly associated with diabetes, whereas other studies have reported the opposite ,,. In the present study, 57.1% of definite dry eye patients had diabetes mellitus. The mechanism for increased occurrence of dry eye in diabetes mellitus is unclear. It is possible that damage to the microvasculature of the lacrimal gland together with autonomic neuropathy may contribute to impaired function of the gland. Sensory neuropathy of the cornea may also play a role. Moreover, the various medications used by diabetic patients may exacerbate the dry eye state . Other postulations include the involvement of aldose reductase, the first enzyme of the sorbitol pathway. The oral administration of aldose reductase inhibitors has been shown to improve tear dynamics significantly .
DED was higher (49%) in the patients with previous LASIK surgery (n = 285), as refractive surgery affect corneal nerves either by severing or by ablation, resulting in high incidence of postoperative DED .
This study reveals the higher prevalence of DED among smokers (either active or passive), reaching 52.8%. A study conducted by El-Shazly et al. in Egypt to detect the effect of passive smoking on tear film status in children found that 74.2% had dry eye symptoms and signs. This is consistent with the results of Lee et al. in Indonesia, which revealed a 1.5-fold increase in DED in smokers. However, McCarty et al. found no association despite running multivariate logistic regression models in the Melbourne study. There have been discrepancies in associating MGD with specific clinical features of dry eye. Results from a Chinese and Taiwanese study showed no correlation of MGD with dry eye symptoms  or Schirmer's test , whereas in the Salisbury Eye Study MGD was associated with dry eye symptoms . Moreover, several population-based studies reporting dry eye ,,, have not reported its relationship with MGD.
| Conclusion|| |
The prevalence of DED among adult ophthalmic outpatients at Sohag University Hospital, Egypt, was 22.8%. Older age and female sex were the significant sociodemographic predictors of DED. The unique environmental characteristics may also have a role in the magnitude of the problem of DED. The importance of trying to outline the demographics of DED in our community lies in its irritative symptoms, which can be debilitating and result in both psychological and physical effects compromising the quality of life. In addition, DED should be taken more seriously both by the physician and by the patient to guarantee both high index of suspicion for the physician and compliance on the patient part. Future population-based surveys on DED types are warranted to unravel the subtypes of DED in our environment and to determine whether there are risk factors that can be avoided. 
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]