Are We Missing Amblyopia? The Answer: Preschool Screening
Amblyopia is a reduced visual acuity in one eye that is not related to obvious structural or pathological anomalies.1 Most authors do not include organic causes of reduced vision such as cataract, retrolental masses, scarred cornea, chorioretinitis, and tumors in the group of patients having amblyopia. Visual acuity must be measured under monocular conditions. If a child is allowed to use his one normal eye while the visual acuity is measured, the amblyopia will go undetected. By carefully occluding one eye while the vision is measured in the fellow eye, an accurate evaluation is obtained. The diagnosis is made when there is at least a two-line difference in Snellen test types between the two eyes, e.g., 20/20 in one eye and 20/30 in the opposite eye. A conservative estimate has shown that at least 2% of the population has amblyopia.2 Amblyopia is a common finding in children with strabismus.3 If a child has strabismus, the parents and the pediatrician notice that something is wrong with the child's eyes. But, what about the child who has amblyopia and straight eyes? What percentage of children with amblyopia have straight eyes, and how can we be sure not to miss the diagnosis in these patients? The answer is early preschool screening. The earlier the amblyopia is detected, the better the prognosis for successful treatment and the shorter the duration of intensive therapy. A prospective study was carried out to determine what percentage of children with amblyopia have straight eyes. The results also show what percentage of patients with amblyopia might be missed if we check visual acuity only in children with strabismus.