Effects of Various Risk Factors on Myopia Progression

Background: myopia has different prevalence rate worldwideand there is controversial points about its environmentalrisk factors. the prevalence of myopia in medicalinterns at shiraz medical school and its probable risk factorswere studied.method: in this retrospective cross-sectional study, threehundred interns (ih-year medical students) at shiraz universityof medical sciences were examined by auto refractometerand subjective refraction. we also administered a questionnaireto evaluate the age of the onset of myopia, the power ofthe first spectacles, and its power in the first year of medicalschool, parental refractive error, prematurity, mean amount oftime spent for studying, sleeping, and tv watching per dayamong myopic students and a comparable control group.results: ninety-two out of 300 (31%) interns had myopiaover 0.5 diopters with similar age, sex, time spent for sleepingand studying as 88 randomly selected non-myopic controls.parental myopia was reported in 54% of cases and 25%of controls (p(less than)0.05). 60% of myopic interns had more than0.75 diopters of progression during medical school years withsimilar age, sex, and time spent for sleeping and studying as40% with less than 0.75 diopters of progression. mean age ofonset of myopia was 17.00(plus-minus)2.88 years with mean initialamount of -0.96(plus-minus)0.45 diopters in former subgroup, but inthe latter subgroup, these were 13.84(plus-minus)2.99 years and 1.37(plus-minus)1.40 diopters, respectively (p(less than)0.05).conclusion: those students with myopia progression duringmedical study had later onset with less amounts of initial myopiathan those without progression during the same period.