|Year : 2020 | Volume
| Issue : 2 | Page : 80-83
Association between pterygium and dry eye among patients in Benghazi, Libya
Osama M Omran, Samar A Bukhatwa
Department of Ophthalmology, Faculty of Medicine, University of Benghazi, Benghazi, Libya
|Date of Submission||21-Nov-2019|
|Date of Acceptance||29-Apr-2020|
|Date of Web Publication||22-May-2020|
Dr. Samar A Bukhatwa
Department of Ophthalmology, Faculty of Medicine, University of Benghazi, Benghazi
Source of Support: None, Conflict of Interest: None
Background and Aim: Pterygium is a relatively common condition of the conjunctiva that affects people at different stages of life. Dry eye disease (DED) is a well-known associated morbidity with pterygium. The aim of this study was to investigate the association between pterygium and dry eye among otherwise healthy Libyan people. Methods: A case–control study was conducted on patients attending Al-Keish Polyclinic in Benghazi. Two techniques have been applied individually, in parallel and in series for all of the study participants, Schirmer's test and break-up time (BUT) test. Results: This study included 50 eyes belonged to 35 patients with a median age of 37 (range 26–65) years, and among those, 18 (51.4%) cases (25 eyes) had pterygium and a group of 17 (48.6%) cases (25 eyes) were control. Rates of DED diagnosis were highest using parallel testing (positive results in any of the tests) than with BUT and Schirmer's test individually and lowest using series testing (positive results in both tests). Eyes with pterygium showed obviously and statistically significant higher rates of positive test results. All controls were normal testing with Schirmer's test and hence in series testing. Conclusion: Testing for DED using parallel combined testing (BUT and Schirmer's test) relying on positive result of any of the tests increases sensitivity and may increase the value of the test for screening for dry DED among particular high-risk groups.
Keywords: Break-up time test, dry eye disease, pterygium, Schirmer's test
|How to cite this article:|
Omran OM, Bukhatwa SA. Association between pterygium and dry eye among patients in Benghazi, Libya. Libyan J Med Sci 2020;4:80-3
| Introduction|| |
Dry eye disease (DED) is a common worldwide multifactorial disease of the tears and ocular surface that causes tear film instability with possible damage to the ocular surface. The prevalence of dry eye in the world population ranges from 6% to 34%. It is more common in those aged over 50 and affects mainly women. Pterygium is frequently associated with DED, and many authors believe that pterygium might be a causative factor for DED. There is a suggested effect of pterygium on corneal biomechanical properties as a possible mechanism that might explain the relationship between pterygium and DED. A recent study suggested a low tear production in the eyes with nasal primary pterygium but no effect on intraocular pressure. Tests used to elicit signs of DED include determining the tear film break-up time (BUT), corneal fluorescein staining score, and Schirmer's tests.
As DED is expected to be common in dry areas such as Libya and frequently observed in ophthalmology outpatient clinics, as well as the importance of pterygium as a potential cause for partial loss of vision, the research in this area is warranted to fill a gap in our knowledge about the behavior of these two conditions in relation to each other at the local level. Therefore, the aim of this study was to investigate the association between pterygium and dry eye among otherwise healthy Libyan people attending the outpatient ophthalmology services.
| Methods|| |
An open-labeled case–control (comparative) study was designed, and the data were collected as primary data with direct interviewing and examining a sample of patients attending Al-Keish Polyclinic in Benghazi during the last 4 months of 2016. Ethical approval was obtained from the Research Ethics Committee, Department of Ophthalmology, Faculty of Medicine, University of Benghazi, and written informed consent was obtained from patients before their enrollment.
Inclusion and exclusion criteria
Case series of Libyan patients of both genders attending the ophthalmology clinic as nonoperated cases of pterygium, either unilateral or bilateral, were included. The control group has been chosen included eyes of patients with similar criteria but attending for another eye complaint rather than pterygium., Pterygium size was graded according to the following; Type I: extends <2 mm into cornea, Type II: involves up to 4 mm of the cornea, and Type III: invades more than 4 mm of the cornea and involves the visual axis. Only pterygia of Grades 2 and 3 were included. Cases with chronic disease such as diabetes, hypertension, or rheumatologic disorder; those on chronic or recent topical eye treatment; or those with prominent chronic eye disease might be related to xerophthalmia or recent ophthalmological surgery were excluded.
Two techniques have been used in parallel for all of the study participants, Schirmer's test and BUT test. A cutoff level of <5 mm in 5 min for Schirmer's test and in <10 s for BUT was applied as the definitions for DED. Parallel testing which means that any test positive means positive result regardless other test result was applied and labeled as “any test.” Further, series testing was applied which means that both tests are required to be positive to consider the result positive for DED and labeled as “both tests.” Tear function tests (i.e. Schirmer's and the BUT test) were performed by the same examiner.
Schirmer's (basic secretion) test was performed as described in the literature, following instillation of one drop of benoxinate hydrochloride 0.4% (Benox – E.I.P.I.CO., Egyptian Int. Pharmaceutical Industries Co, Egypt) by placing a sterile Schirmer's test paper (Ophthalmic diagnostic strip – Schirmer's tear test by Optitech Eyecare). BUT test was performed using fluorescein strips (OptiGlo strips by Ophtechnics Unlimited). The test was repeated three times, and the average value was recorded.
The statistical package for social science (SPSS) software version 20.0 (SPSS Inc., Chicago, IL, USA) has been used to analyze data. Interpersonal comparison was performed using Chi-square test (likelihood and Pearson's) and its alternative Fisher's exact test when nonapplicable. Fisher's exact test has been applied in the situation that expected frequencies are too small. Mann–Whitney U-test was used because of nonnormality of numerical variables when making eye to eye comparison. Any test result with P < 0.05 was considered statistically significant.
| Results|| |
A total number of 35 patients (50 eyes) were enrolled. A number of 18 (51.4%) cases (25 eyes) with pterygium and a control group of 17 (48.6%) cases (25 eyes) with other complaints other than pterygium were examined. In case of pterygium, bilateral eyes were examined in 7 (38.9%) patients; right eye only in 9 (50.0%) patients; and left eye only in 2 (11.1%) patients. Eyes examined as bilateral ones were 14 in number (56% of total pterygium eyes). In control group: bilateral eyes, eight patients (47.1%); right eye only, six patients (35.3%); and left eye only, three patients (17.6%). Eyes examined as bilateral eyes were 16 in number (64% of total control eyes). Male contributes for 83% of pterygium cases and 88% of control cases. There was no statistical difference between male and female according to pterygium cases. In pterygium cases, the median age was 37 years (range 26–65).
Analysis of indices of dry eye disease in the total study population
Analysis was applied to 50 eyes, 25 with pterygium and 25 without pterygium. Rates of DED diagnosis were highest using parallel testing (any test positive = DED) than with BUT and Schirmer's tests and lowest using series testing (both tests positive = DED). Eyes with pterygium showed obviously higher rates of positive test results. All of controls were normal testing with Schirmer's test and hence in series testing [Figure 1].
|Figure 1:Rates of dry eye disease according to different tests among the total study population|
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Schirmer's test was positive in 40% of eyes with pterygium but none among controls (P < 0.001). BUT test showed a higher rate of DED (88%) among pterygium eyes compared to 40% among controls, with odds ratio of 11 and 95% confidence interval; 2.6–46.8. Difference in the results of parallel testing (Schirmer's or BUT test positive) between pterygium and control groups was also statistically significant (P < 0.001). Moreover, difference in the results of series testing (Schirmer's and BUT test positive) between pterygium and control groups was statistically significant (P = 0.002).
Analysis of indices of dry eye disease in gender subgroups
In males subgroup, both Schirmer's and BUT test results were statistically significant (P = 0.001 and P = 0.003, respectively). Using parallel testing (Any test positive = DED) and series testing (Both test positive = DED) in males were also statistically significant (P = 0.001 and P = 0.004, respectively) [Figure 2]. Among females, BUT test and parallel testing were positive in all cases of pterygium, but no significant differences could be elicited [Figure 3].
|Figure 2: Rates of DED according to different tests among the male's subgroup|
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|Figure 3:Rates of DED according to different tests among the female's subgroup|
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| Discussion|| |
In this study, the rates of DED diagnosis were highest using parallel testing (positive results in any of the tests) than with BUT and Schirmer's test and lowest using series testing (positive results in both tests). Eyes with pterygium showed obviously higher rates of positive test results. All controls were normal testing with Schirmer's test and hence in series testing. No difference in the pterygium rate across male and female groups was detected. Although the number of females in the study was considerably small, researches on whether gender is related to pterygium have been uncertain. Nevertheless, Detorakis and Spandidos reported a slightly higher incidence in males in many countries.
Schirmer's test in this study was positive in 40% of eyes with pterygium but none among controls. This rate was higher than world population as reported by Valim et al. Although abnormal Schirmer's test results in the pterygium patients have been conflicting, Manhas et al. found that Schirmer's test values were significantly reduced in the eyes with pterygium than control. Many other researchers also found that Schirmer's test value with anesthesia was decreased significantly in eyes with pterygium when compared with a healthy eye.,, On the other hand, other studies found no significant difference in Schirmer's test between pterygium patients and controls.,,
In the present study, BUT test showed a higher rate of DED that was 88% among pterygium eyes compared to 40% among controls. The results were higher than world population estimates. Unlike the Schirmer's test results in the various studies, results of tear BUT have shown abnormal values in almost all the previous studies as it can be seen with the results of El-Sersy TH, Bekibele et al. and Rajiv who reported that BUT values were significantly reduced in cases of pterygium when compared with control eyes indicating the inadequacy of tear film in these patients.,, Rajab suggested several mechanisms that can cause the reduced tear BUT test in eyes with pterygium, such as compromised eyelid blinking, that may cause dehydrated epithelium, thus leading to shorter tear BUT test; in addition, the presence of pterygium causes irregularity in the surface epithelium that can compromise the surface tension and tear stability. He proposed that the abnormality of tear BUT test, which was found more frequently in the eyes with pterygia than eyes without pterygia, suggests that there may be an abnormality of mucin which may be a predisposing factor for the pathogenesis of pterygium or that pterygium itself causing abnormalities of mucin.
Combining tests in parallel increased sensitivity to DED among pterygium eyes as 92% but not among controls. Nevertheless, the difference is still significant. Male subgroup showed also a higher DED rate which was 90.9% among pterygium eyes compared to 45.5% among controls. Series testing decreased sensitivity for DED to the rate of 36% among pterygium which is still at the upper limit of worldwide population compared to 0% among controls. Further, among male subgroup, DED was 36.4% among pterygium eyes and 0% among controls. The result was statistically significant and consistent with the findings reported by Valim et al. The prevalence rate of DED was lower with Schirmer's score (17.8%) than with tear BUT test (34.2%), and a difference between the two tests was also found in another study, though only significant among specific particular groups according to etiology. Sensitivity of Schirmer's test may be changed with modified technique.
Limitations and drawbacks of the study include that the number of females was small, and the total number of study population was also very small, so studies with higher sample size will be considered with control eyes belonging to the same person with pterygium in the other eye to eliminate systemic factors.
| Conclusion|| |
This study has demonstrated that DED is a common significant problem that most prevail among pterygium patients. It can lead to vision-threatening complications. Thus, treatment of dry eye should also be part of pterygium management. Testing for DED using BUT test seems very sensitive while testing with Schirmer's test shows very high specificity among patients with pterygium. Parallel combined testing relying on positive result of any of the tests increases sensitivity and may increase the value of the test for screening for DED among particular high-risk groups.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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