title: Prevalence of myopia and its risk factors in urban school children in Delhi: the North India Myopia Study (NIM Study).
abstract: OBJECTIVE
  Assess prevalence of myopia and identify associated risk factors in urban school children.
  
  
  METHODS
  This was a cross-sectional study screening children for sub-normal vision and refractive errors in Delhi. Vision was tested by trained health workers using ETDRS charts. Risk factor questionnaire was filled for children with vision <6/9.5, wearing spectacles and for a subset (10%) of randomly selected children with normal vision. All children with vision <6/9.5 underwent cycloplegic refraction. The prevalence of myopia <-0.5 diopters was assessed. Association of risk factors and prevalence of myopia was analyzed for children with myopia and randomly selected non myopic children and adjusted odds ratio values for all risk factors were estimated.
  
  
  RESULTS
  A total number of 9884 children were screened with mean age of 11.6 + 2.2 years and 66.8% boys. Prevalence of myopia was 13.1% with only 320 children (24.7%) wearing appropriate spectacles. Mean myopic spherical error was -1.86 + 1.4 diopters. Prevalence of myopia was higher in private schools compared to government schools (p<0.001), in girls vs. boys (p = 0.004) and among older (> 11 years) children (p<0.001). There was a positive association of myopia with studying in private schools vs. government schools (p<0.001), positive family history (p< 0.001) and higher socio-economic status (p = 0.037). Positive association of presence of myopia was observed with children studying/reading > 5 hours per day (p < 0.001), watching television > 2 hours / day (p < 0.001) and with playing computer/video/mobile games (p < 0.001). An inverse association with outdoor activities/playing was observed with children playing > 2 hours in a day.
  
  
  CONCLUSIONS
  Myopia is a major health problem in Indian school children. It is important to identify modifiable risk factors associated with its development and try to develop cost effective intervention strategies.
authors.affiliation: Department of Ophthalmology, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Rohit
authors.initials: R
authors.lastname: Saxena
authors.affiliation: Department of Community Ophthalmology, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Praveen
authors.initials: P
authors.lastname: Vashist
authors.affiliation: Department of Ophthalmology, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Radhika
authors.initials: R
authors.lastname: Tandon
authors.affiliation: Department of Biostatics, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: R M
authors.initials: RM
authors.lastname: Pandey
authors.affiliation: Department of Community Ophthalmology, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Bhardawaj
authors.affiliation: Department of Ophthalmology, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Vimala
authors.initials: V
authors.lastname: Menon
authors.affiliation: Department of Biostatics, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Kalaivani
authors.initials: K
authors.lastname: Mani
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D009216:Myopia / Q000453:epidemiology*; D015995:Prevalence; D012307:Risk Factors; D012959:Socioeconomic Factors; D013334:Students / Q000706:statistics & numerical data; D014505:Urban Population / Q000706:statistics & numerical data