Development of grating acuity, letter acuity, and visual fields in small-for-gestational-age preterm infants

Visual acuity and visual field development were assessed longitudinally in 21 preterm children who were born small-for-gestational-age (SGA) and in 51 preterm children who were appropriate-for-gestational-age (AGA). Grating acuity was tested binocularly at 0-1 month and monocularly at 4, 9, 12, 18, 24, 30, 36 and 48 months corrected age, using Teller acuity cards. Visual fields were measured binocularly using kinetic perimetry at the same ages. Recognition (letter) acuity testing was attempted using the crowded HOTV test in all subjects who came in for testing at 36 and 48 months. Children in the SGA group were matched to children in the AGA group by gestational age (+/- 3 weeks) and type of perinatal medical complications. There were no significant differences in grating acuity or binocular visual field size between the SGA and AGA groups. 78% of acuity scores for individual SGA-AGA pairs fell within one octave of perfect agreement. Binocular visual field size for each SGA-AGA pair also showed good agreement. Fewer SGA than AGA subjects were able to perform recognition acuity testing, and those SGA subjects who were able to perform the test, showed consistently poorer recognition acuity than their AGA counterparts. Thus, being SGA does not pose an additional risk for the development of grating acuity or binocular visual field size over the first 4 years of life in preterm children. SGA preterm children may be at risk, however, for acuity deficits when acuity is measured with the more complex targets and the greater test distance used to measure recognition acuity.