Background Screening is the presumptive identification of individuals in a population at risk likely to be affected by an asymptomatic or subclinical condition who can benefit from further investigation.1 In children, eye screening is the process of detecting amblyopia, strabismus, significant refractive error and other vision disorders to ensure early intervention in order to guarantee optimal visual outcome during the critical period in early life. Aim To carry out an eye screening to assess the prevalence and determine the causes of visual impairment in preschool age children attending nursery and primary schools in Ilorin East Local Government Area of Kwara State, and to assess the utility of the Lea symbols chart as a screening tool in these children. Methods The study was a descriptive, cross-sectional school-based study in which data collection spanned from September 30, 2013 to February 14, 2014. A total of 464 children comprising 109 children from 5 public schools and 355 children from 7 private schools in Ilorin East Local Government Area were enrolled into the study by a multistage sampling procedure. Visual acuity (VA) of selected children was checked using the Lea symbols chart. Children meeting the referral criteria (modified from the American Academy of Ophthalmology Preferred Practice Pattern® Guidelines on Pediatric Eye Evaluations) of visual acuity worse than 20/30 (6/9.5), two lines of difference in visual acuity between the eyes; visible anterior and posterior segment anomalies; and untestable children with the Lea symbols thereafter had a comprehensive eye examination comprising a cycloplegic retinoscopy and dilated fundoscopy. Visual impairment was defined as the presence of an identifiable structural cause of reduced vision among children that failed or were untestable. Amblyopia was defined as a difference of two lines or more between the two eyes in best corrected visual acuity, in the presence of an amblyogenic risk factor. Amblyopia was also defined as improvement in visual acuity using a single optotype chart, in the absence of an organic lesion. Myopia was defined as spherical equivalent (SE) −0.50 diopters (D) or more. Hyperopia was defined as SE +2.00 D or more. Astigmatism was defined as cylinder power 1.00 D or more at any axis, and anisometropia was defined as a SE difference 1.00 D or more between the 2 eyes.