Visual Acuity and Stereoacuity

Visual acuity improvement in infancy and early childhood is attributable to neural development as well as ocular structural changes (see Chapter 16).

Two major methods are used to quantitate visual acuity in preverbal infants and toddlers: preferential looking (PL) and visual evoked potential (VEP). See Chapter 1 for a description of these methods. VEP studies show that visual acuity improves from approximately 20/400 in newborns to 20/20 by age 6–7 months. However, PL studies estimate the visual acuity of a newborn to be 20/600, improving to 20/120 by age 3 months and to 20/60 by 6 months. Further, PL testing shows that visual acuity of 20/20 is not reached until age 3–5 years. The discrepancy between measurements obtained by these 2 methods may be related to the higher cortical processing required for PL compared with VEP. Stereoacuity reaches 60 seconds of arc by about age 5–6 months (see Chapter 7).

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.