Approximately 7% of children in the United States younger than 18 years have a diagnosed eye disorder, and 1 in 4 children between two and 17 years of age wears glasses. Routine eye examinations during childhood can identify abnormalities necessitating referral to ophthalmology, which optimizes children's vision through the early diagnosis and treatment of abnormalities. The U.S. Preventive Services Task Force recommends vision screening at least once in children three to five years of age to detect amblyopia or its risk factors to improve visual acuity. The American Academy of Family Physicians supports this recommendation. The American Academy of Pediatrics recommends screening starting at three years of age and at regular intervals in childhood, and that instrument-based screening (e.g., photoscreening, autorefraction) is an alternative to vision charts for testing visual acuity in patients three to five years of age. Eye examinations include visual acuity testing, external examinations, assessing ocular alignment and pupillary response, and assessing for opacities with the red reflex examination. Common abnormalities include refractive errors, amblyopia (reduction in visual acuity in one eye not attributable to structural abnormality), and strabismus (misalignment of the eye). Rare diagnoses include retinoblastoma (often detectable through loss of red reflex), cataracts (detectable by an abnormal red reflex), and glaucoma (often manifests as light sensitivity with corneal cloudiness and enlargement).