Abstract
Background: Refractive errors are one of the most leading causes of visual impairment worldwide. It is caused by eye’s inability to focus the light properly therefore causing a blurred vision. There are three major types: myopia, hyperopia, and astigmatism. We aim to determine the prevalence of refractive errors among medical students at Qassim University, to identify types of refractive errors and to assess the association between near work hours per day and the presence of refractive errors.
Methods: This cross-sectional study was conducted at Qassim university, Saudi Arabia, outpatient clinics. Using sample size calculation sample size of 362 students was approximated. Students were examined in the ophthalmology clinic at Qassim university outpatient clinics for the presence and the degree of refractive error. Students were interviewed by trained interviewers about demographic data, general health status, and history of refractive errors and associated risk factors.
Results: A total of 603 medical students participated in the study of which 568 (94.0%) had refractive errors and the remaining 35 (6.0%) students were Plano (normal). The most refractive errors in the examined sample were myopia and astigmatism (56.3% and 22.4%, respectively) and these were more prevalent among the age group of 19-22 years old. Myopia was the common errors of refraction among female and more among the fifth year. There was a significant increase in astigmatism among juniors in medical school (p = 0.002). Also,the most significant risk factors among studied sample which increases in myopia and astigmatism were daily
outdoor activities less than or equally to 1 hour (p = 0.04 and p = 0.05, respectively) and the daily outdoor activities more than 3 hours during childhood (p = 0.05).
Conclusion: The prevalence of refractive errors among studied sample was 94% which is one of the highest rates reported, myopia is the most common, regular screening program and checkup for early detection and correction is recommended to prevent impairment of the vision.

Key words: Refractive errors, myopia, hyperopia, astigmatism, medical students