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ORIGINAL ARTICLE
Year : 2020  |  Volume : 47  |  Issue : 3  |  Page : 176-179

Correlation between ocular sun exposure and pterygium: A hospital-based study


1 Department of Ophthalmology, Dr. D.Y Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra, India
2 Department of Pathology, Dr. D.Y Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra, India

Date of Submission01-May-2020
Date of Acceptance18-Jul-2020
Date of Web Publication21-Jan-2021

Correspondence Address:
Dr. Banyameen Iqbal
Department of Pathology, Dr. D.Y Patil Medical College, Hospital and Research Center, Pimpri, Pune - 411 018, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jss.JSS_34_20

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  Abstract 


Background: The term “pterygium” comes from the Greek word “Pterygos,” which means “wing.” The major predisposing factors are the hot and dry climate and long periods of ultraviolet light exposure. Epidemiological studies have revealed that the prevalence of pterygium is inversely related to latitude, and that it is greater among outdoor workers than indoor workers. Although sun exposure has been accepted as a risk factor for pterygium, there is no objective diagnostic tool to measure the total amount of sun exposure of an individual. Materials and Methods: This is a prospective study carried out for a period of 1 year on 100 eyes with pterygium. Demographic variables including age, sex, residence, education, income, smoking, alcohol drinking, exercise, and especially sun exposure were collected from interviewing the patients as per the pro forma. Their occupation was categorized according to the fields of profession. A detailed eye examination which included slit-lamp examination, visual acuity, refractive status, and size of the pterygium was recorded. The size of the pterygium was measured in millimeters from its apex to the limbus using the slit-lamp beam. Pterygium was graded, depending on the extent of the corneal involvement, and all the patients were divided into five grades (Grades I to V). Results: Out of 100 pterygia, 89' were located nasally, whereas only 11' were temporal. Nearly 84' of the total pterygia were found in unilateral eyes, whereas only 16' were seen in bilateral eyes. The male-to-female ratio was 1.8' (65 males: 35 females). Nearly 35' of the pterygia were seen in middle-aged males (41–60 years), followed by 20' in 21–40 years' age group. Grade III pterygium was seen in 15' of male patients in 41–60 years' age group, whereas only 8' were seen in the same age group in females. Maximum number of patients having pterygium 10' (Group B) and 15' (Group C) showed a maximum duration of daylight exposure of 8 and 10 h, respectively. Conclusion: This study shows that outdoor work and sunlight exposure are positively associated with the development of pterygium. Besides sun exposure, other factors which favor pterygium formation such as dusty environment, smoking, and genetics should also be taken into consideration, and further research should be done to ascertain their role in pterygium formation. Public education should focus on encouraging people to take appropriate protective measures, such as wearing sunglasses and brimmed hats when outdoors, and to avoid unnecessary sunlight exposure.

Keywords: Outdoor work, pterygium, sun exposure


How to cite this article:
Mushtaq I, Maghdum R, Bhavsar D, Iqbal B. Correlation between ocular sun exposure and pterygium: A hospital-based study. J Sci Soc 2020;47:176-9

How to cite this URL:
Mushtaq I, Maghdum R, Bhavsar D, Iqbal B. Correlation between ocular sun exposure and pterygium: A hospital-based study. J Sci Soc [serial online] 2020 [cited 2021 Feb 25];47:176-9. Available from: https://www.jscisociety.com/text.asp?2020/47/3/176/307596




  Introduction Top


The term “pterygium” comes from the Greek word “Pterygos,” which means “wing.”[1] Although usually small and benign in nature, pterygia are common; cause considerable irritation, astigmatism, and cosmetic concerns; and often recur after surgical removal.[2] Its incidence is more in tropical and subtropical regions between 30° latitude north and south of the equator. The incidence of pterygium in India is on an average 5.2' (ranging from 0.075' in Punjab to 10.42' in Maharashtra).[3],[4]

The major predisposing factors are the hot and dry climate and long periods of ultraviolet (UV) light exposure. Epidemiological studies have revealed that the prevalence of pterygium is inversely related to latitude, and that it is greater among outdoor than indoor workers. Although sun exposure has been accepted as a risk factor for pterygium, there is no objective diagnostic tool to measure the total amount of sun exposure of an individual.[5]

Patients who are younger than the age of 15 years rarely acquire a pterygium. Although the prevalence of the lesion increases with age, the highest incidence occurs between the ages of 20 and 49 years.[6] Pterygium is commonly seen in India, which is a part of the “pterygium” belt. Some studies found a statistically significant association between the UV light exposure (both UV-A and UV-B) and the development of pterygium in a large group of Chesapeake Bay fishermen.[7] UV light exposure may not be the only factor which is associated with the development of pterygium. One study of pterygium, which was done among welders who were exposed to increased levels of UV light, showed a direct relationship between the lengths of their employments and the incidence of pterygium.[8]


  Materials and Methods Top


This is a prospective study carried out for a period of 1 year ranging from January 2017 to December 2018. One hundred eyes with pterygium, presenting in the ophthalmology outpatient department, in a tertiary care hospital in western Maharashtra, India, were included in the study. Ethical and scientific committee approvals for conducting the study were taken. Well-informed consents from the patients enrolled in the study were also obtained.

Demographic variables including age, sex, residence, education, income, smoking, alcohol consumption, exercise, and especially sun exposure were collected from interviewing the patients as per the pro forma. Their occupation was categorized according to the fields of profession as office workers, service industry, agriculture, technician, laborer, or none (including homemaker and student). The area of residence was categorized as urban and rural. Education was categorized into high school education of =12 years or higher education. Smoking status was divided into current smokers and nonsmokers (including ex-smokers), and alcohol consumption status was divided into heavy drinkers and moderate drinkers to nondrinkers. Sunlight exposure was categorized as an average of <2, 2–5, or >5 h of sunlight per day.

A detailed eye examination which included slit-lamp examination, visual acuity, refractive status, and size of the pterygium was recorded meticulously. Patients with a history of trauma and/or a previous eye surgery and patients having a history of corneal scars or any other eye surgery were not included in the study.

All patients were examined using slit-lamp biomicroscopy. The size of the pterygium was measured in millimeters from its apex to the limbus using the slit-lamp beam. Pterygium was graded, depending on the extent of the corneal involvement, and all the patients were divided into five grades (Grades I to V):

  • Grade I – Just touching the cornea
  • Grade II – Encroaching 1 mm onto the cornea
  • Grade III – Encroaching 2 mm onto the cornea
  • Grade IV – Encroaching 3 mm onto the cornea
  • Grade V Encroaching >3 mm onto the cornea.


Depending on the basis of age, the patients were divided into four groups (Groups A to D):

  • A: 0–20 years
  • B: 21–40 years
  • C: 41–60 years
  • D: >61 years.



  Results Top


Out of 100 pterygia, 89' were located nasally, whereas only 11' were temporal. Nearly 84' of the total pterygia were found in unilateral eyes, whereas only 16' were seen in bilateral eyes. The male-to-female ratio was 1.8' (65 males: 35 females). A significant gender difference was seen with almost twice the number of males as compared to females. Maximum number of pterygium (35') was seen in middle-aged males (41–60 years), followed by 20' in 21–40–years' age group [Table 1].
Table 1: Age and sex distribution among the patients

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Grade III pterygium was seen in 15' of male patients in 41–60 years' age group, whereas only 8' were seen in the same age group in females. Similarly, only 10' and 6' of Grade III pterygia were seen in males and females in 21–40 years' age group, respectively. On the other hand, only 10' and 6' of the cases in Grade II group were males and females, respectively [Table 2].
Table 2: Comparison of age groups with the grade of pterygium

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Correlation of pterygium size with the duration of outdoor working hours was also noted in different age groups [Table 3]. It is worth mentioning here that as the duration of working hours increases, the frequency and the grade of pterygium also increase, although not proportionately. There are some other factors which are responsible for the formation of pterygium besides the UV ray exposure. In our study, we found a negligible number of patients (2') having pterygium in the age group of <20 years, who were having 3 h or less of UV exposure. Maximum number of patients having pterygium 10' (Group B) and 15' (Group C) showed maximum duration of daylight exposure of 8 and 10 h, respectively.
Table 3: Relationship of average working hours (outdoor) with age and grade of pterygium

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  Discussion Top


The most important risk factor in the development of pterygium is UV ray exposure, although it may not be the only factor. In our study, we also found that the incidence of pterygium formation is proportional to the daily sunlight exposure (UV rays). This finding is comparable to the findings of other workers worldwide.[9],[10],[11],[12]

Other than sunlight exposure, other factors responsible for the causation of pterygium as concluded by some other studies are dust exposure in outdoor workers.[10],[11] In our study also, we found more number of pterygium patients to be outdoor workers rather than indoor workers.

In our study, we found the increase in incidence as well as grade of pterygium as the age of the patient increases. This might indicate the cumulative effect of exposure to sunlight over the years, whereby solar radiation may initiate ocular tissue changes that later promote the development of pterygium in the later years. Our study was in accordance with the studies done by other authors.[13],[14]

Effect of previous or present use of protective sunglasses against pterygium formation is highly debatable. Several studies done in this regard show mixed results with no to high protective index of the use of sunglasses which block UV-A and/or UV-B radiations.[9],[13] Moreover, the use of protective glass lenses in comparison to plastic lenses is also shown to be less effective in the protection against pterygium as glass is known to be less effective in blocking UV-B radiation.[15]

Genetic attributes and variable lifestyle behavior such as smoking and working in a dusty environment may also contribute to pterygium formation besides sun exposure.[13],[15]

A major limitation of our study was that the data on the average daily UV light exposure in patients were solely dependent on the patient's inputs and there were no means available to us to accurately measure the actual duration of sunlight exposure. Second, the relatively small sample size might have made some factors, such as smoking, insignificant, in contrast to some previous studies where the sample size was large enough.


  Conclusion Top


This study shows that outdoor work and sunlight exposure are positively associated with the development of pterygium. Public education should focus on encouraging people to take appropriate protective measures, such as wearing sunglasses and brimmed hats when outdoors, and to avoid unnecessary sunlight exposure. Meanwhile, further research is required to enable us to better understand the relative contributions of different risk factors such as smoking, dusty environment, and genetics.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of inter?est.



 
  References Top

1.
Coster D. Pterygium-an ophthalmic enigma. Br J Ophthalmol 1995;79:304-5.  Back to cited text no. 1
    
2.
Errais K, Bouden J, Mili-Boussen I, Anane R, Beltaif O, Meddeb Ouertani A. Effect of pterygium surgery on corneal topography. Eur J Ophthalmol 2008;18:177-81.  Back to cited text no. 2
    
3.
Mushtaq I, Magdum R, Buch A, Iqbal BM, Arun S, Malhotra J. Study to correlate clinical and histopathological characteristics of pterygium in predicting its recurrence. J Med Soc 2017;31:190-4.  Back to cited text no. 3
  [Full text]  
4.
West S, Muñoz B. Prevalence of pterygium in Latinos: Proyecto VER. Br J Ophthalmol 2009;93:1287-90.  Back to cited text no. 4
    
5.
Li Z, Wu S, Mai J, Xu K, Sun Y, Song Z, et al. Prevalence of and risk factors for pterygia in a rural Northern Chinese population. Ophthalmic Epidemiol 2014;21:378-83.  Back to cited text no. 5
    
6.
Lin A, Stern G. Correlation between pterygium size and induced corneal astigmatism. Cornea 1998;17:28-30.  Back to cited text no. 6
    
7.
Paton D. Pterygium management based upon a theory of pathogenesis. Trans am Acad Ophthalmol Otolaryngol 1975;79:603.  Back to cited text no. 7
    
8.
Moran DJ, Hollows FC. Pterygium and ultraviolet radiation: A positive correlation. Br j Ophthalmol 1984;68:343-46.  Back to cited text no. 8
    
9.
Rosenthal FS, Bakalian AE, Lou CQ, Taylor HR. The effect of sunglasses on ocular exposure to ultraviolet radiation. Am J Public Health 1988;78:72-4.  Back to cited text no. 9
    
10.
Mackenzie FD, Hirst LW, Battistutta D, Green A. Risk analysis in the development of pterygia. Ophthalmology 1992;99:1056-61.  Back to cited text no. 10
    
11.
Nakaishi H, Yamamoto M, Ishida M, Someya I, Yamada Y. Pingueculae and pterygia in motorcycle policemen. Ind Health 1997;35:325-9.  Back to cited text no. 11
    
12.
Wong TY, Foster PJ, Johnson GJ, Seah SK, Tan DT. The prevalence and risk factors for pterygium in an adult Chinese population in Singapore. The Tanjong Pagar Survey. Am J Ophthalmol 2001;131:176-83.  Back to cited text no. 12
    
13.
Khoo J, Saw SM, Banerjee K, Chia SE, Tan D. Outdoor work and the risk of pterygia: A case-control study. Int Ophthalmol 1998;22:293-8.  Back to cited text no. 13
    
14.
Threlfall TJ, English DR. Sun exposure and pterygium of the eye: A dose-response curve. Am J Ophthalmol 1999;128:280-7.  Back to cited text no. 14
    
15.
Tan D, Lim AS, Goh HS, Smith DR. Abnormal expression of the P53 tumour suppression gene in the conjunctiva of patients with pterygium. Am J Ophthalmol 1997;3:404-5.  Back to cited text no. 15
    



 
 
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  [Table 1], [Table 2], [Table 3]



 

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