|Year : 1983 | Volume
| Issue : 6 | Page : 723-728
The epidemiology of high myopia-chanding trends
IS Jain, Sandeep Jain, Kanwar Mohan
Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
I S Jain
Deptt. of Opthalmology, PGIMER, Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Jain I S, Jain S, Mohan K. The epidemiology of high myopia-chanding trends. Indian J Ophthalmol 1983;31:723-8
The aetiopathogenesis of myopia is not well understood and many factors have been held responsible from time to time e.g. excessive convergence (Von-Graefe 1854) 1, excessive accommodation (Donders 1864) 2, congestion of ocular coats, disorders of ocular growth, avitaminosis and endocrine dysfunction (Duke Elder 1970) 3. The biological theory of myopia views that myopia is a result of genetically determined characteristics of various eye tissues whereas the use-abuse theory implies that continual near work causes myopia. The influence of hereditary factors has been studied extensively; some workers favouring it (Sourasky 4-1928, Duke Elders-1954) whereas others (Thompson 1910 6, Doyne 7-1923) holding the hereditary influence questionable. Various prenatal, perinatal and post natal environmental factors have been found to be operating in causation of myopia (Brian 1970) 8. The purpose of this paper is to elucidate the role played by various environmental and genetic factors in causation of high myopia and to find out any changing trends in epidemiology with the passage of time.
| Method and materials|| |
The following surveys and studies were conducted by the senior author I. S. Jain.
1. Survey of 4001 school children of both rural and urban origin.
2. Survey of 12743 persons living in two rural blocks of Haryana and Punjab.
3. Survey of urban population of Chandigarh which included 10509 persons.
4. A study of 124 families which included 142 high myopes (Myopia more than 6D) to investigate the mode of inheritance of high myopia.
From Jan. 1980-December 1981
5. A study of 14756 patients who attended eye OPD of one units in Eye Department of PGIMER, Chandigarh (mostly urban).
To find out any changing trends in eqidemiology of high myopia, the data of above surveys was compared with that of 1966 reported by the senior author.
| Observations|| |
Prevalence: Surveys from 1967-1972 have shown a higher prevalence of myopia in school children (4.79%), urban population of Chandigarh (6.9%) and patients attending Eye OPD-mostly urban (12.2%) in comparison to rural population (2.77%). 3.65% of the myope school children had high myopia versus 13.4% of urban and 15.7% of Eye OPD .myopic population [Table - 1].
Study of 5000 eye OPD patients in year 1966 has shown 15% incidence of myopia of which 16% had high myopia.
Age: 6-12 years age group formed the major bulk (71.87%) of the school children suffering from myopia. In both rural and urban populationincidence of myopia decreased after 3rd decade. In urban set up incidence of high myopia was found to increase up to 5th decade [Table - 2]. In the previous study in year 1966, maximum number of high myopes were in 2nd and 3rd decade.
Sex: A higher incidence of myopia was found in male school children whereas in rural and urban population no significant sex predominance was seen [Table - 3]. Also no sex predominance was found in urban high myopes. However male high myopes outnumbered females in ratio of 2:1 in year 1966 study.
Social status: (as indicated by per capita income)
Incidence of myopia was found to increase with increase in the social status of the patients [Table - 4].
A review of medical board cases from April 1979 to March 1982 has shown a higher incidence of myopia in doctors in comparison operative problems were encountered in a minority of eyes [Table - 7]. 6/12 or better vision could be achieved in 58.6% of eyes [Table - 9].
to class III and class IV employees [Table - 5].
In another study 405 of 638 (63.48%) of high myopes were persons engaged in strenous near work versus 233 of 638 (36.52%) of those not much involved in near work. Student community alone constituted 40.75% of the total high myopes.
Heredity: A total 727 members of 124 families were studied which included 142 high myopes and 103 low myopes.
No high myopia was found in the parents of 57 propositi out of a total of 67 propositi [Table - 6]. Also a low frequency of high myopia was found in siblings than in parents. 5 out of 219 siblings had high myopia against 11 out of 134 parents [Table - 6] and none out of 193 siblings against 59 out of 114 parents [Table - 7].
Surgery in high myopes
(a) Cataract surgery (58 eyes)
48 of the 58 eyes underwent intracapsular cataract extraction while 10 eyes had extracapsular cataract extraction. There was no operative complication and only few post operative problems were encountered in a minority of eyes [Table - 8]. 6/12 or better vision could be achieved in 58.6% of eyes [Table - 9].
(b) Retinal detachment surgery (67 eyes)
Successful anatomical apposition could be achieved in 94% of eyes. 6/18 or better vision was achieved in 34,4% of eyes [Table - 10].
| Discussion|| |
Various hereditary and environmental factors have been postulated to understand the aetiopathogenesis of myopia. In the present study a higher incidence of myopia was found in school children (4.79%) and urban population (6.9-12.2%) in comparison to rural population (2.77%). When compared with 1966 year figures, there has been no significant difference in the prevalence of simple as well as high myopia in eye OPD population (Mostly urban). A higher incidence in school children and urban set up supports the near work postulate; the former two groups being actively engaged in enar work. This has also been amply proved by the studies of other workers (Yamaji et al 1972, Richter et al 1980). 71.87 of total myopic children were 6-12 years age group. In rural and urban population the prevalence of myopia decreased after 3rd decade perhaps because of decline in near work activities especially studies. However high myopia showed decline after 5th decade indicating the role of factors other than near work. Study in year 1966 has shown high myopia to be twice more common in males than females whereas in the present studies (1967-1972 and 1982), there was equal affection of both the sexes. This may perhaps be due to more involvement of females in academic activities now than a decade and half ago. The factor of near work in causation of myopia is also supported by our observation as 63.48% of high myopic patients were students and professionals engaged in near work; the former alone constituted 40.75% of high myopic population. A higher incidence of myopia with increase in social status of the patients [Table - 4] can be attributed again to the literary achievements and involvement in near work. Near work has been explained to cause myopia by increasing axial length of the eye ball by means of accommodation and convergence mechanisms have been demonstrated to cause increase in pressure in the posterior of the eye as well as traction on sclera resulting in an increase in axial length of the eye ball (Gold schmidt 1981).
In the study of 124 families to elucidate inheritance of high myopia, no high myopia was found in the parents of 57 propositi out of a total out of question. Further there is a significantly lower frequency of high myopia (3 out of 180) among the sibling of the propositi when neither parent has high myopia than when there is high myopia in one or both parents (2 out of 39) indicating that irregular dominance is not very likely. Goldschmidt 1963 also reported similar results. Inheritance of high myopia being autosomal receissive also appears wrong because in our study 5 out of 219 siblings had high myopia against 11 out of 134 parents. In recessive inheritance the frequency should be high in siblings than in parents. So from familial investigation it is concluded that high myopia has no common genetic background.
Further the senior author has observed many low myopes (47 out of 638-7.3%) with no hereditary basis progressing to high myopia which again lays stress on the environmental factors like age, sex, urbanisation, literary achievement, socio-economic status etc. rather than heredity alone being the prime aetiological factor. The genetic factors modified by environmental factors thus seem to best explain the aetiopathogenesis of high myopia and points towards the multifactorial mode of inheritance.
The vitreous being degenerative, the fear of vitreous loss has deferred many surgeons from undertaking intracapsular cataract extraction in high myopes and the fear of post operative shallow anterior chamber has further added to their nervousness. However those who dared, have not come across much difficulty. Our observations have also proved that this fear is unfounded as we faced no operative complication in any of the 48 eyes where lens was extracted intracapsularly and very few minor post operative problems were encountered in a minority of eyes. Also the visual results have been satisfactory (6/12 or better vision in 58.6% eyes) inspite of the associated degenerative fundus changes. Retinal detachment also posed no special problem in management and successful anatomical apposition could be achieved in 94% of eyes with 6/18 or better vision in 34/3% eyes.
| Summary|| |
An analysis of 4001 school children, 12743 persons living in rural area, 10509 persons of urban set up; & 14756 patients attending eye OPD of PGIMER, Chandigarh (mostly of urban origin) is reported. A higher incidence of myopia was found in school children and urban population, high social status persons and those involved in near work activities laying stress on the factor of near work in the causation of myopia. Study of 124 families to elucidate the inheritance of high myopia revealed no common genetic background for high myopia. It is concluded that genetic factor modified by environmental factors determine the development of myopia. When compared with figures of year 1966, incidence of high myopia has remained almost same though more involvement of females has brought the male-female affection equal in comparison to males predominance a decade and half ago. Fear of complications in cataract extraction and retinal detachment surgery in high myopia has been proved unfounded.
| References|| |
Von-Gracie, A 1954, A.F.O., 1:283 (1-167).
Donders, F.C. 1954, On the anomalies of accommodation and refraction of the eye. The New Syndrenham Society, London, p. 283-448, 557-654.
Duke Elder, W.S., System ofOphtalmology Vol.5, p 300.
Sourasky A. 1928, Br. Jr. Ophthal.. 12: 197-212.
Duke Elder, W.S 1954, Practice of Refraction, Philadelphia, The Blackiston Company, 18: 77-92.
Thompson, Ophthal. Rev. 29,321 (1910).
Doyne, P.G., Themyopic child, Clin. J. 52: 157 (1923).
Brian J. Curtin, Survey of Ophthal Vol. 15/1; 1-19 (1970).
Jain, I.S. and Singh, Kapalmit, Orient Arch. Ophth. 5, 67-75 (1967).
Yama Ji and Yashida S., Folia Ophthal. Japn. 23: 267 91972).
Richler A and Bear J.C., Acta Ophthalmol. (KbH) 58: 468-478 (1980).
Gold Schmidt Ernst, Acta Ophthalmol 59:
Goldschmidt, 1968, Acta Ophthalmol, Supplimentum, 98.
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6], [Table - 7], [Table - 8], [Table - 9], [Table - 10]
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