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Correlates of myopia in students of Bahauddin Zakariya University, Multan.

Byline: Mushtaq Hussain Lashari, Ruby Ayub, Muhammad Saleem Akhtar, Mazhar Ayaz and Zahida Tasawar

Abstract

The present study was conducted to determine the prevalence of myopia in young students of Bahaudin Zakariya University, Multan. A total sample of 620 students of both gender (male=295; female=325) was collected during 2014. The data was divided in two breeding pattern groups, five groups on account of age at myopia onset and different family size. Out of 620 subjects, 150 had myopia (male=85; female=65). The overall prevalence of myopia was 24.19%. The myopia prevalence was apparently higher in males 28.8% as compared to females 20%. It was observed that myopia was more in age group 21 (37.33%) and less in age group 18 (2.67%). Myopia was found to be higher in inbreeding group (cousin marriage) 56.67% when compared with out-breeding group 43.33% and was found significantly (P18 years and who gave informed consent was included in the study. Foreigner students and the ones diagnosed with other ocular diseases such as amblyopia, squint or cataract were excluded. The survey was completed by the help of a qualified optometrist. The distant visual acuity of each eye was measured using Snellen's E-chart at 6 m with standard lighting. An automatic refractometer (Topcon RM-A7000; Topcon Co., Tokyo, Japan) was used to obtain a measurement of the refractive error without cycloplegia, and the average value of three repetitions was recorded. Parameters used were gender, age, breeding pattern and family size.

All the required information was ascertained from an interview with the students having myopia. Two types of ages were ascertained; 1). Present age and 2). Age at myopia onset. On the basis of present age the sample was divided in six groups, 18, 19, 20, 21, 22, 23 and on account of age at myopia onset the sample was divided in five groups, 5, 10, 15, 20, 25. Breeding pattern of their parents was ascertained and on this basis the sample was categorized in two groups i.e. inbreeding and out-breeding. This data was classified in three groups with different family size, 5, 6-9 and 10. The results are mainly expressed as percentages. The data was analyzed statistically by routine statistical tests for the calculation of percentage. The comparison of various percentages for different parameters were executed by Chi-square test and P-values 0.05). The results regarding the different age groups showed prevalence of myopia was 2.67, 4.67, 23.33, 37.33, 24 and 8% in age groups 18, 19, 20, 21, 22 and 23years respectively. The prevalence of myopia was found highest in age group 21 and lowest in age group 18. It was found that the prevalence of myopia was significantly different in different age groups (c2=85.56; DF=5; P 0.05). The results regarding the age at onset of myopia showed significant (c2 = 86. 2; DF = 4; P 0.05) prevalence of myopia was 2, 30, 36.67, 30 and 1.33% in age groups <5, <10, <15, <20 and <25 respectively. The prevalence of myopia was found highest in age group <15 and lowest in age group 0.05). The prevalence of myopia was 5.33, 69.33, and 25.33% in family size groups 5, 6-9 and >10 respectively. The prevalence of myopia was found highest in family size group 6-9 and lowest in family size group <5. Myopia was significantly different in different family size groups (c2 = 34.27; DF = 2; P < 0.05).

Discussion

During the present study the overall prevalence of myopia was 24.19% among students from different academic and socioeconomic backgrounds in B.Z. University. The present findings are in agreement with previous study in US 25% and Western Europe 26%.5 This result is higher than similar reported studies in Pakistan 8.9%6 and 21.9%,7 in Malaysia 7.7%,8 and in Iran 3.5%.9

These variations may be explained by the different diagnostic criteria used by different authors, racial or ethnic variations in the prevalence of refractive errors, different lifestyles or living conditions. Perhaps a high level of prolonged near work and less time outdoors is the main reason. Recent studies presented robust support to the importance of time spent outdoors on the incidence of myopia.10

The difference could be due to either continued myopia progression or selection of more academic and more myopic students for postgraduate studies.2

The present study indicated that male (28.8%) and female (20%) had non significantly different prevalence of myopia. Our findings are comparable with the earlier work in KPK province, Pakistan.7

It was found that maximum prevalence of myopia was in the individuals who are 21 years of age. Kempen5has shown that myopia develops at all ages but the prevalence of myopia was significantly higher after the age of fourteen.

The world wide reports showed that myopia is rare before school age, gradually rises during school life and reaches its highest level of prevalence during the years of most intense study at the university.6,7 According to the results of present study, myopia was more prevalent in inbreeding group as compared to out-breeding group. This finding supports the previous reports,3 which have shown that myopia in parents may influence the genesis of myopia in their offspring and children with myopic parents are more likely to be myopic. There is tendency for myopia to run in families, children have about a 30 percent chance of developing myopia with one myopic parent and a 55 percent chance with two.3

The prevalence of myopia was found highest in family size group 6-9 and lowest in family size group 5. The literature survey indicated that work on the prevalence of myopia with respect to family size has not been carried out, so comparable data for this parameter is not available.

Many investigations have been carried out during the last 150 years to detect factors, which cause myopia. A factor that has been awarded particular attention in addition to hereditary factors is the influence of the environment, especially the amount of close work on the refractive state of the eye.4 Many theories were proposed to explain the appearance and progression of myopia. But the two most important theories are: 1) The biological theory of myopia or heredity theory and 2) The use-abuse theory of myopia or close work theory.4 The biological hypothesis of myopia views myopia as the result of genetically determined characteristics of eye tissues, whereas the use-abuse theory views myopia as the result of regular use of the eye at a close to focal length, near work. The use-abuse theory means that myopia is preventable whereas the biological theory does not.5

In conclusion, the results of the present study revealed that multiple factors probably combine to cause myopia. We suggest that myopia is partly inherited and partly environmental. An individual's genetics, together with their exposure and susceptibility to environmental factors, probably all have an effect on the structure of the eye. When both parents are nearsighted, their children have a greater than average chance of developing myopia.

Disclaimer: None.

Conflict of Interest: None.

Funding Sources: None.

References

1. Resnikoff S, Pascolini D, Mariotti SP, Pokharel GP. Global magnitude of visual impairment caused by uncorrected refractive errors in 2004. Bull World Health Organ 2008; 86: 63-70.

2. Holden BA, Sulaiman S, Knox K. The Challenge of Providing Spectacles in the Developing World. Community Eye Health 2000; 13: 9-10.

3. Yu L, Li ZK, Gao JR, Liu JR, Xu CT. Epidemiology, genetics and treatments for myopia. Int J Ophthalmol 2011; 4: 658-69.

4. Sherwin JC, Hewitt AW, Coroneo MT, Kearns LS, Griffiths LR, Mackey DA. The association between time spent outdoors and myopia using a novel biomarker of outdoor light exposure. Invest Ophthalmol Vis Sci 2012; 53: 4363-70.

5. Kempen H. Approximately one-third of people older than 40 have vision disturbances. Arch. Ophthalmol 2004; 122: 495-505.

6. Alam H, Siddiqui MI, Jafri SI, Khan AS, Ahmed SI, Jafar M. Prevalence of refractive error in school children of Karachi. J Pak Med Assoc 2008; 58: 322-5.

7. Abdullah AS, Jadoon MZ, Akram M, Awan ZH, Azam M, Safdar M, et al. Prevalence of uncorrected refractive errors in adults aged 30 years and above in a rural population in Pakistan. J Ayub Med Coll Abbottabad 2015; 27: 8-12.

8. Hashim SE, Tan HK, WanHazabbah W, Ibrahim M. Prevalence of refractive error in Malay primary school children in suburban area of Kota Bharu, Kelantan, Malaysia. Ann Acad Med Singapore 2008; 37: 940.

9. Fotouhi A, Hashemi H, Khabazkhoob M, Mohammad K. The prevalence of refractive errors among schoolchildren in Dezful, Iran. Br J Ophthalmol 2007; 91: 287-92.

10. Sun J, Zhou J, Zhao P, Lian J, Zhu H, Zhou Y, et al. High Prevalence of Myopia and High Myopia in 5060 Chinese University Students in Shanghai. Invest Ophthalmol Vis Sci. 2012; 53: 7504-9
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Publication:Journal of Pakistan Medical Association
Geographic Code:9PAKI
Date:Dec 31, 2017
Words:1585
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