IMPORTANCE This follow-up study of extremely preterm (EPT) children (<27 weeks gestational age [GA] at birth) revealed major eye and visual problems in 37.9%(147 of 388) of all EPT infants and in 55.4%(67 of 121) of the most immature subgroups at 6.5 years of age. These major eye and visual problems were strongly associated with treatment-requiring retinopathy of prematurity (ROP). OBJECTIVES To investigate the ophthalmologic outcome of a national cohort of EPT children at 6.5 years of age and to evaluate the impact of prematurity and ROP. DESIGN, SETTING, AND PARTICIPANTS All surviving EPT children born in Sweden between April 1, 2004, and March 31, 2007, were included and compared with a matched term control group, as part of a prospective national follow-up study. MAIN OUTCOMES AND MEASURES Visual acuity, refraction in cycloplegia, and manifest strabismus were evaluated and compared with GA at birth and with treatment-requiring ROP. RESULTS The study cohort comprised 486 participants. The mean (SD) GA of the children who were included was 25 (1) weeks, and 45.7%(222 of 486) were female. At a median age of 6.6 years, 89.3%(434 of 486) of eligible EPT children were assessed and compared with 300 control group children. In the EPT group, 2.1%(9 of 434) were blind, 4.8%(21 of 434) were visually impaired according to the World Health Organization criteria, and 8.8% (38 of 434) were visually impaired according to the study criteria. Strabismus was found in 17.4% (68 of 390) and refractive errors in 29.7%(115 of 387) of the EPT children compared with 0% (0 of 299) and 5.9% (17 of 289), respectively, of the control children (P<.001). Altogether at 6.5 years of age, 37.9%(147 of 388) of the EPT children had some ophthalmologic abnormality compared with 6.2%(18 of 290) of the matched control group (95% CI of the difference, 26.1%-37.2%). When treatment-requiring ROP was adjusted for, no significant association between GA and visual impairment could be detected. For refractive errors, the association with GA remained after adjustment for treatment-requiring ROP (odds ratio, 0.72; 95% CI, 0.58-0.91 for each 1-week increment). CONCLUSIONS AND RELEVANCE In a Swedish national cohort of EPT children at 6.5 years of age, major eye and visual problems were frequently found. Treatment-requiring ROP was a stronger impact factor than GA on visual impairment and strabismus, but not on refractive errors, as a whole. In modern neonatal intensive care settings, ophthalmologic problems continue to account for a high proportion of long-term sequelae of prematurity.