Prevalence of Conditions Causing Visual Impairment in Students at the Oklahoma School for the Blind

Abstract

In the United States, approximately 0.15% to 0.17% of the population aged 18 years or younger is visually impaired (Nelson & Dimitrova, 1993; Wall & Corn, 2004). Studies of schools for students with visual impairments and state-wide pediatric low vision programs (DeCarlo & Nowakowski, 1999; Ingelse & Steele, 2001; Wilkinson & Stewart, 1996; Wilkinson & Trantham, 2004) as well as national surveys (Kong et al., 2012; Steinkuller et al., 1999) investigated the prevalence of conditions responsible for vision loss in children and youths. This study reports on the conditions that are responsible for causing visual impairment (that is, blindness or low vision) in students enrolled at the Oklahoma School for the Blind (OSB). We compared our findings to a study conducted 27 years previously at the same location (Miller & Edmondson, 1988). Methods This was a retrospective study of data from students enrolled at OSB. Permission was granted by the Northeastern State University Institutional Review Board and officials at OSB. OSB staff members gathered date of birth, gender, diagnosis primarily responsible for vision loss, and best-corrected visual acuity information from students' medical files and in some cases consulted us when they needed clarification. Whenever possible, the visual information was taken from examination records from the clinic operated at OSB by the Northeastern State University Oklahoma College of Optometry (NSUOCO). Students' names were not recorded. Records from all 93 students enrolled at OSB during the 2013-2014 academic year were reviewed and are represented in this study. Students enrolled at OSB are required to meet at least one of three admission criteria (Oklahoma School for the Blind, 2015): corrected visual acuity of 20/70 or less; visual field no greater than 20 degrees in the better eye; or visual impairment which, even with the best correction, adversely affects performance in a regular class. We used the same diagnostic categories as were used in the previous study (Miller & Edmondson, 1988), but for the categories of Congenital malformations and Other we also reported specific diagnoses. RESULTS The student population we studied was 57.0% male and 43.0% female, similar to that examined by Miller and Edmondson (1988), which included 90 students who were 55.6% male and 44.4% female. Gender distribution between the two studies was not statistically significant ([X.sup.2] = .04, p = 0.85). Our students were on average about 2 years older than in the previous study (14.2 years vs. 12.2 years in 1987), but the age difference was not statistically significant ([X.sup.2] = 3.85, p = 0.28) (see Table 1). Most of the visual acuities in our study were measured in the clinic operated by NSUOCO, where the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart was used and visual acuity was interpolated from the total number of optotypes correctly identified (Ferris, Kassoff, Bresnick, & Bailey, 1982). Visual acuities in 1987 were evaluated with the Feinbloom chart. Due to gaps between acuity categories in the 1987 study, we rounded the visual acuity of our students who fell in those gaps to the nearest category and reported them accordingly. Furthermore, we included two additional visual acuity categories that were not utilized in 1987 to provide more detail about students in the lower end of the visual acuity spectrum. In our study, 40 of 93 students (43.0%) had visual acuity worse than 20/400, the usual definition of blindness internationally, and 54.8% had visual acuity worse than 20/200. In 1987, 54.4% of students had distance visual acuity worse than 20/200. With Yates correction applied, the differences in visual acuity between the two studies were not statistically significant ([X.sup.2] = 7.13, p = 0.31) (see Table 2). The primary purpose of our investigation was to compare the prevalence of conditions causing visual impairment at the same school in 1987 and 2014. …