Purpose: To evaluate the prevalence of refractive errors, strabismus and reduced contrast sensitivity in an unselected group of children with developmental delay (DD), and to propose extensions to the existing guidelines to assess the number of examinations required to optimally support children with DD.
Methods: A total of 923 children with IQ < or = 80, aged 4-15 years, from Copenhagen County, Denmark, were ophthalmically examined. The prevalence of refractive errors and strabismus and the presence of reduced contrast sensitivity were recorded and related to level of IQ.
Results: Among the 923 children, the following prevalences were found: significant hyperopia (> or = + 3 D) 15.3%; myopia (< - 0.5 D) 10.8%, and astigmatism (< - 1 cyl D) 20.6%. Strabismus was found in 26.8% of subjects (esotropia in 14.9%, exotropia in 10.3%, and other forms, including mixed types, in 1.6%). Refractive errors and strabismus were significantly correlated with low IQ. Reduced contrast sensitivity was correlated with age, visual acuity and level of IQ.
Conclusions: To our knowledge, this study is the largest on ocular disorders in children with DD. Hyperopia, astigmatism, anisometropia, strabismus and contrast sensitivity had a high prevalence, and all disorders were related to low IQ. According to the extended guidelines, an annual minimum of 565 examinations per 100 000 children (0-17 years) is required to optimally support children with DD.