title: Refractive errors of medical students in Turkey: one year follow-up of refraction and biometry.
abstract: OBJECTIVE
  This study was conducted to determine the prevalence of refractive errors in Turkish medical students as well as to determine the change in refractive status of medical students within 1 year. Besides general refractive characteristics of the students, the possible relationship between the occurrence of myopia and several factors was also determined.
  
  
  METHODS
  Two hundred and seven medical students (114 female/93 male) were checked for their refractive status as determined by cycloplegic autorefraction. In addition to keratometric and biometric measurements students also answered a detailed questionnaire. One year later, medical students who participated to the study were re-examined.
  
  
  RESULTS
  Myopia occurred in 32.9% of medical students with low myopia (spherical equivalent between -0.75 diopters [D] and -2.99 D) being the most common type (81%). The frequency of myopia was not significantly different between female and male medical students (37.7 and 26.8%, respectively; p=0.13). Adult onset myopia (onset at age 18 years or older) comprised 14.7% of all myopia cases. Myopic students were significantly more likely to report parental myopia. The percentage of myopes and nonmyopes reporting having one or two myopic parents was 51.5 and 28.8%, respectively (p=0.002). Parental myopia was also an independent risk factor associated with the occurrence of myopia on multivariate analysis (odds ratio [OR]=3.69, 95% confidence interval [CI]=1.98-6.87). Nonmyopes also reported a significantly higher prevalence of outdoor activity before and at age seven (68.4%) than did myopes (48.6%), (p=0.009). Outdoor activity during early childhood was found to be protective for myopia on multivariate analysis (OR=0.44, %95 CI=0.23-0.82). There was no significant difference between myopes and nonmyopes with respect to amount of close-up activity. No significant shift of refraction occurred within 1 year.
  
  
  CONCLUSIONS
  About one-third of Turkish medical students had myopia. Parental myopia was more common among myopic students and was a risk factor for the occurrence of myopia suggesting a familial predisposition. Outdoor activity in early childhood has had a protective role against the development of myopia in this study sample.
authors: Department of Ophthalmology, Marmara University School of Medicine, Istanbul, Turkey. sumruo_md@yahoo.com
authors: Sumru
authors: S
authors: Onal
authors: Ebru
authors: E
authors: Toker
authors: Ziya
authors: Z
authors: Akingol
authors: Gul
authors: G
authors: Arslan
authors: Semra
authors: S
authors: Ertan
authors: Can
authors: C
authors: Turan
authors: Onur
authors: O
authors: Kaplan
mesh_terms: D000293:Adolescent; D000328:Adult; D000867:Anterior Chamber / Q000473:pathology; D001699:Biometry / Q000379:methods; D003315:Cornea / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D012189:Retrospective Studies; D017678:Sex Distribution; D013337:Students, Medical; D014421:Turkey / Q000453:epidemiology; D014822:Vitreous Body / Q000473:pathology