Pinguecula is a benign, round, protruding lesion in the interpalpebral fissure adjacent to the limbus but not over the cornea. It is usually bilateral, more often at the nasal rather than the temporal limbus. Pinguecula develops because of an alteration of healthy tissue, where stromal collagen is replaced with thicker fibers.1–5 Although pinguecula resembles lipid deposition, histopathological studies show that it is composed of degenerate, basophilic, and subepithelial tissue similar to pterygium.6 The etiology and pathogenesis of this common degenerative disease of the conjunctiva are still unclear.7 Several causes such as age,8–12 ultraviolet (UV) radiation,8–12 elevated cholesterol metabolism,13 dust exposure,14 elastotic degeneration,15 alcohol intake,8 and dry eye3 have been implicated in the development of pinguecula.
It was shown that tear-film function alteration was a possible change inducing pinguecula formation.3 Wearing contact lens (CL) can cause CL-related dry eye and alterations of the tear film, which affect nearly half of all CL wearers.16,17 To our knowledge, only one study has explored the relationship between wearing CL and pinguecula formation in which the authors did not evaluate the participants regarding dry eye disease.18 In this study, we aimed to investigate the effects of CL on the frequency of pinguecula. Besides, pinguecula may cause dry eye symptoms, such as burning sensation, itching, stinging, blurred vision, and foreign-body sensation. We further evaluated the effects of pinguecula on such ocular symptoms.
MATERIAL AND METHODS
The authors adhered to the Declaration of Helsinki and all state laws, and the patients were asked to give consent before being enrolled in the study. This study was approved by the local ethics committee of the Ministry of Health at Dokuz Eylül University. In this study, 233 cases of 285 soft CL users who gave consent to the study were enrolled between July 2017 and June 2018. A group of 230 age-matched nonwearers without any ophthalmologic disorders other than refractive problems served as controls. A questionnaire including ocular surface disease index (OSDI), age, sex, and duration of CL wear was implemented before all subjects were examined.
Ocular Surface Disease Index Questionnaire
Before the ocular examination, all participants were required to complete the OSDI questionnaire, a 12-item patient-reported outcome questionnaire designed to quantify visual disability due to dry eye. Subjects were evaluated in three different subscales: ocular symptoms (e.g., “do your eyes feel gritty?”), vision-related function and limitations (e.g., “do you have problems with your eyes that limit you in reading?”), and environmental triggers (e.g., “have your eyes felt uncomfortable in windy conditions?”) during a 1-week recall period. Each answer was scored based on the frequency of symptoms using a 5-point scale from 0 (indicating no problem) to 5 (indicating a significant problem). Responses to all questions were combined for a composite OSDI score ranging from 0 to 100, with higher scores indicating more severe symptoms. The same ophthalmologist (H.D.) explained the questionnaire to participants if they had difficulty in reading and assisted when required.
The ocular examinations were performed at the same location by the same ophthalmologist (H.D.) using the same instruments. A comprehensive anterior segment examination, including eyelids, lacrimal system, conjunctiva, cornea, sclera, iris, and lens, was performed under a slit-lamp microscope. Pinguecula must be distinguished from pterygium, pseudopterygium, and conjunctival neoplasm; therefore, the diagnosis of pinguecula was made when the typical yellowish lesion that forms on the nasal or temporal conjunctiva was present. Apart from routine slit-lamp examination, tear film break-up time test (TBUT) and Schirmer I test (ST) were also performed. The examination was performed in conformity to the procedures described in a previous report.19 Patients with systemic disease, previous ocular surgery, ectropion, entropion, and proptosis, and patients using regular topical medication were excluded from the study.
The paired or unpaired Student's t-test was used to compare the mean values between the two groups, and the chi-square test was used to compare categorical data. The level of significance was set at P<0.05 for all analyses, which were performed with the Stat View statistical software package (Abacus Concepts, Berkeley, CA).
Table 1 shows the characteristics of CL wearers and the controls. No significant differences were found between two groups concerning age and sex. The prevalence of pinguecula was 27.8% (n: 65) in the CL group and 26.5% (n: 61) in the control group (P=0.841) (Table 2). The prevalence of pinguecula was found to increase with age in both groups (Table 2). The prevalence of pinguecula in men and women was the same in the CL group (P=0.902), whereas the prevalence was higher in men in the control group (P=0.013). In the CL group, in 84.7% of the patients, pinguecula was present in both eyes and 66.1% was localized on nasal conjunctiva. In the control group, 83.7% of the patients had pinguecula in both eyes, and it was localized on nasal conjunctiva in 68.8%. There was no significant difference in the location of pinguecula between CL wearers and nonwearers in each age group (P>0.05).
The mean CL-wearing time was 12.8±5.9 years. Figure 1 shows the prevalence of pinguecula according to the CL wear time. There was no significant difference in the prevalence of pinguecula when users were divided into three groups according to the time of CL wear (P=0.575).
The TBUT scores were lower in the CL group than the control group (Table 3). In both groups, the TBUT scores were lower in patients with pinguecula. The OSDI scores were higher in the CL group (Table 3). There was no significant difference regarding the OSDI scores between patients with pinguecula and healthy participants in the CL group; however, the OSDI scores were significantly higher in patients with pinguecula in control group (Table 3). There were no significant differences in the ST between CL wearers and controls, and between patients with pinguecula and healthy participants.
The triggering factors in the pathogenesis of pinguecula are not well-determined; however, several factors have been associated with pinguecula formation, including age,8–12 UV radiation,8–12 dust,14 and alcohol.8 To the best of our knowledge, only one study has explored the effects of CL wearing on pinguecula prevalence where it was shown that both the prevalence and grade of pinguecula were higher in CL wearers than those who are not.18 However, in that study, the authors did not evaluate the participants concerning dry eye disease. They also reported that the prevalence of pinguecula increases with longer duration of CL wear. They attributed this increase to constant friction and inflammation of the conjunctiva caused by the CL edge. In accordance, they reported a higher prevalence of pinguecula in those wearing hard CL, which causes more inflammation and friction compared with soft CL. In our study, there was no difference in pinguecula prevalence between soft CL wearers and nonwearers, and CL-wearing time did not affect the prevalence of pinguecula. The reason for these conflicting results might be the improvements in CL technology. Mimura et al.18 reported their study in 2010, and there have been many improvements in CL technology since then. It was previously reported that new generation soft CLs cause less inflammation than and do not disrupt the tear film stability as much as the older ones due to their lower modulus and higher oxygen permeability.20 Furthermore, new generation CLs provide more protection against UV light, which is a well-known risk factor for pinguecula formation.
In agreement with previous studies, pinguecula was usually bilateral, more often at the nasal than the temporal limbus.6 The reason for nasal localization of pinguecula might be that UV light affects nasal conjunctiva more than temporal conjunctiva.21 It was reported that pinguecula prevalence was higher in men than women because men spent more time outside, and they are exposed to sunlight more than women. Viso et al.8 reported similar sun exposure time and similar pinguecula prevalence for women and men. In our study, there was no difference between men and women in the CL group regarding pinguecula prevalence; however, pinguecula prevalence was higher among men than women in the control group. We did not evaluate participants in terms of occupation; however, we might speculate that those in the CL group might have a higher socioeconomic status considering the costs of CLs and most of them might have in-office jobs, whereas a higher proportion of the control group might have outside jobs. As a result, those in the control group might have spent more time outside and exposed to sunlight more.
The effects of CL wearing on tear-film stability have been shown in many studies.16,17,22 It has been reported that there was no difference between CL wearers and controls regarding the ST scores, and that the TBUT scores were lower and the OSDI scores were higher among CL wearers compared with the controls.6,20,21,23 In our study, the comparison of the ST, TBUT, and OSDI scores of CL wearers and controls yielded similar results.
There are conflicting results regarding the ST results in patients with pinguecula. Oguz et al.3 reported that there was no difference in the ST scores between patients with pinguecula and healthy subjects, whereas Le et al.24 reported that there was a decrease in the ST scores in pinguecula patients. In agreement with Oguz et al., we found no significant difference in the ST scores between pinguecula patients and healthy subjects.
There are consistent results regarding the TBUT scores in pinguecula patients. In agreement to Oguz et al., we found that the TBUT scores were significantly lower in those with pinguecula than the controls in both CL wearers and nonwearers. The lower TBUT scores might be caused by several mechanisms in such eyes: normal eyelid blinking might be compromised in the eyes with pinguecula, and this may lead to desiccated epithelium resulting in less wettability and a shorter TBUT. Furthermore, pinguecula causes an elevation and irregularity on the surface epithelium; thus, the tear layer becomes thinner. This thinning may alter the balance between lipid and mucus layers in the tear film, which is very important for tear film stability. When tear film is disrupted, it evaporates rapidly and results in a shorter TBUT.
The OSDI questionnaire is a survey in which participants are subjectively evaluated regarding dry eye symptoms. There are many studies, which suggest CL wearing induces dry eye disease.16,17,22 Consistent with them, the OSDI scores were higher in CL wearers than nonwearers in our study. Pinguecula causes symptoms such as itching, stinging, and foreign-body sensation similar to dry eye disease. We expected and found higher OSDI scores in patients with pinguecula compared with the control group. However, in the CL group, there was no difference between patients with pinguecula and healthy participants regarding the OSDI scores. The reason for this might be that soft CLs cover the limbus and the pinguecula to some extent, and it may decrease the symptoms related to pinguecula. Furthermore, it has been reported that changes in corneal nerve plexus occur, and corneal sensitivity decreases with continuing CL wearing.25,26 As a result, it may prevent the effects of pinguecula on cornea causing uncomfortable symptoms. Further longitudinal studies are needed to evaluate the CL effects on pinguecula symptoms.
This study has some limitations. Because it is a cross-sectional study, we are not able to fully understand the relationship between dry eye disease and pinguecula. Longitudinal studies are needed to understand whether tear-film instability is a precursor to pinguecula, or pinguecula causes tear film instability. Sunlight exposure and education level are related to pinguecula prevalence; however, we did not evaluate our patients regarding confounding factors such as their education level and occupation.8–10,24 The CL-wearing patients might be more likely to have a better education level; it is possible that they are exposed to sunlight less than control subjects, and these may affect the results of this study.
In conclusion, this is the second study that evaluates the effects of wearing CLs on pinguecula prevalence. Contrary to the previous study, we found that wearing CLs does not affect the prevalence of pinguecula. Furthermore, we evaluated dry eye disease concerning CL use and pinguecula. There was no difference in the ST score regarding CL and pinguecula. The TBUT scores were found to be lower in patients with pinguecula and in patients who wear CL. Despite the lower TBUT, there was no increase in the OSDI scores in patients with pinguecula in the CL group. We think that CL might decrease the symptoms of pinguecula because it covers the pinguecula and decreases the sensitivity of cornea.
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Keywords:© 2019 Contact Lens Association of Ophthalmologists, Inc.
Contact lens; Pinguecula; Dry eye disease