Purpose: Children born preterm are believed to be at increased risk of visual impairment (VI). The increased survival rate of extremely preterm children may have changed the spectrum of diseases occurring postnatally. The aim of this study was to analyse the prevalence and causes of VI in an ex-preterm Danish population during the last 4 decades. Methods: The study was based on the National Register of Blind and Visually Impaired Children (NRVIC). Ex-preterms born at gestational age (GA) <32 weeks and enrolled in NRVIC at any time between 1988 and 2020 were included. The main cause of VI, the severity of VI and systemic comorbidities were analysed for temporal changes. Results: A total of 335 patients were included. The prevalence of VI decreased from 26/1000 preterm children in the 1980s to 15/1000 in 2000s. Blindness due to preterm birth is almost eliminated affecting 1/1000 today. Sequelae to retinopathy of prematurity (ROP) was the most common cause of VI (51% of cases) in the 1980s but decreased to 34% in 2010s, whereas non-ocular causes of VI increased from 1% to 36%, respectively. More than half of the children (64%) had combined comorbidities and 36% had isolated VI. Conclusion: The improved monitoring in neonatal intensive care units and management of ROP has reduced the prevalence of severe VI due to ROP and almost eliminated blindness over the last decades in Denmark. However, preterm children are still at risk of non-ocular causes of VI and comorbidities following the premature delivery.