Children born preterm are at increased risk of reduced visual acuity, refractive errors, strabismus and amblyopia, complications of ROP, CVI, visual field abnormalities and reduced contrast sensitivity. Photo: Getty Images.

Prematurely born children are at risk of numerous complications that affect the visual system. Retinopathy of prematurity (ROP) and cerebral visual impairment (CVI) are among two major causes of childhood blindness and visual impairment in industrialized nations, and large countries are seeing increasing childhood blindness from ROP alone, adding to the burden of disease worldwide. The purpose of this study is to review the long-term impacts of prematurity, ROP and CVI on vision in children who were born preterm, and numerous risk and complications were found.

Topics reviewed include the burden of vision loss in prematurely born children worldwide, a description of ROP and CVI, effects on visual acuity, refractive errors, strabismus and binocularity, visual fields and contrast sensitivity, and risk factors for visual complications.

Children who are most at risk of visual complications are those with the smallest gestational age at birth and birth weight in general. “Although ROP severity and the presence of neurological impairments including CVI play a large role in the development of poor visual outcomes, premature birth alone without CVI or severe ROP increases the risk of future visual complications,” the authors explained. “Awareness of signs and symptoms of CVI are important in the management of affected children.”

Three prospective population-based studies in the past decade show the long-term risks to the visual system. In Norway, among 52 six to seven-year-olds born between 22- and 27-weeks gestation, subnormal vision down by one to two Snellen lines was present in 46% in their best eye, strabismus in 10%, all esotropia (half of those affected did not have ROP or neurological events), mild myopia in 8%, latent strabismus in 51% (all exophoric except one) and nystagmus in two of those with strabismus. In that cohort, 15% had stage 3 ROP or higher, 1% were diagnosed with peripheral vision loss and 26% had intraventricular hemorrhage.

In the UK and Ireland, among 128 19-year-old participants born at 22- to 25-weeks gestation, strabismus was recorded in 36%, nystagmus in 13% compared to 0% for each in the control group and refractive errors in 50% (note that the latter was found in 41% in age matched full-term adults). In that group, 48% did not develop ROP and 13% were treated with laser or cryotherapy.

In Sweden, 59 adults 25 to 29 years of age born less than 34 weeks gestation manifested strabismus in 12% (all with onset less than four years of age, 7% with esotropia and 5% with exotropia), reduced stereoacuity in 36% (vs 2% in the control group), and reduced accommodation and contrast sensitivity in those with subnormal vision.

“Recognizing the risks for CVI, with careful history and examination targeting these complications is critical to optimize the visual outcomes and management of these children and adults with complicated medical histories,” the authors concluded. “A multi-disciplinary approach to the management of individuals born preterm can enable the implementation of strategies that can positively impact their general development, learning abilities and activities of daily living.”