PURPOSE: To investigate the longitudinal development of refraction and strabismus in a national cohort of children born extremely preterm (EPT) and find relations to perinatal events and neurodevelopmental outcomes.

METHODS: All surviving children born <27-gestation weeks in Sweden during April 2004-March 2007, and full-term born matched controls were invited to participate in the 12-year ophthalmological follow-up of the Extremely Preterm Infants in Sweden Study (EXPRESS). Refractive error after cycloplegia and manifest strabismus were studied in relation to gestational age, intraventricular haemorrhage (IVH), retinopathy of prematurity (ROP), ROP treatment, cerebral palsy, cognitive disability and visual impairment.

RESULTS: Refractive error was measured in 309 EPT children and 184 controls, and strabismus was assessed in 332 EPT and 188 controls. In the EPT group, 13.6% (n = 42) had significant myopia, 24.6% (n = 76) had significant hyperopia, and 27.5% (n = 85) had significant astigmatism. The development of spherical refractive error in EPT from 2.5 to 12 years was similar to controls, though the dispersion of values was broader in the EPT group. Myopia was related to ROP treatment; astigmatism was related to ROP treatment and severe IVH. Hyperopia was higher in EPT children without ROP treatment compared to controls. Strabismus was found in 18% (61 of 332) EPT children, 68% had esotropia and 32% exotropia, and was associated with ROP treatment and IVH.

CONCLUSION: EPT birth affects emmetropisation longitudinally, with most EPT children remaining hyperopic, except those treated for ROP. A rising trajectory of strabismus contributes to the complex ophthalmological disabilities challenging children born EPT.