Visual Acuity in Premature Infants

Abstract

Purpose: To measure grating visual acuity in premature infants and compare it with that in full-term infants. Methods: The visual acuity of 73 premature and 73 full-term infants was tested at 6 months of age by the Teller Acuity Card procedure. All premature infants had undergone indirect funduscopy for the detection of retinopathy of prematurity (ROP). Seven infants had developed ROP. The mean gestational age of the premature infants was 33 ± 1.4 weeks as compared with 39.9 ± 0.9 weeks in the full-term infants. The mean birth weights of the 2 groups were 1,906 ± 412 and 3,244 ± 420 g, respectively. Results: Impaired binocular visual acuity was found in 53.4% of the premature infants, but in only 11% of the full-term infants (p < 0.0001). Impaired monocular visual acuity was found in 13.7% of the premature infants as compared with 2.7% of the full-term infants. Within the premature infant group, monocular visual acuity was impaired in 42.9% of those with ROP and in 10.6% of those without ROP (p = 0.0497). Pathological refraction was found in 33.3% of the prematures without ROP and in 14.3% of the prematures with ROP. This difference was not statistically significant. Visual acuity of preterm infants was not different from full-term infants when examined at 6 months of postconceptual age. Conclusions: Both monocular and binocular visual acuities as measured by the Teller Acuity Cards are worse in premature infants than in full-term infants at the same chronological age. Poor visual acuity in premature infants can be attributed mainly to immaturity of the visual system.