This study found esotropia to be the most common type of strabismus developed by individuals who were born preterm. Photo: Shutterstock. Click image to enlarge.

As the number of children born preterm increases, so does the prevalence of associated postnatal ocular conditions, including retinopathy of prematurity (ROP), strabismus and nystagmus. Recent studies have identified rates of childhood strabismus prevalence as high as 42% in preterm individuals, including those with ROP. To identify potential risk factors in this population, a new study assessed the prevalence and associated factors for strabismus, as well as nystagmus, in preterm and full-term infants in adulthood using data from the Gutenberg Prematurity Eye Study. Among its conclusions was that low gestational age and refractive errors are independent risk factors for strabismus, with esotropia being the most common form.

In total, 892 eyes of 450 individuals were included from the Gutenberg Prematurity Eye Study, a retrospective cohort study including preterm and full-term adults between 18 and 52 years old (mean age: 28.6 years). Comprehensive ophthalmological examinations were conducted on all participants, and 16 unique perinatal and actual risk factors were assessed in multivariable analysis to evaluate their association with strabismus and nystagmus.

The cohort was divided into six groups based on gestational age and the presence of ROP. The inclusion criteria for each group, as well as the prevalence of strabismus and nystagmus in each, are described in the table below:

The researchers linked several factors to the presence of strabismus in the multivariable regression model, including gestational age (odds ratio: 0.90), anisometropia ≥1.5D (OR: 3.87), hypermetropia ≥2D (OR: 9.89) and astigmatism ≥1.5D (OR: 2.73). Other significant observations from the analysis included that esotropia was more common than exotropia and hypermetropia/hypometropia; most patients developed strabismus within the first 10 years of life; and perinatal adverse events were the strongest predictor associated with nystagmus (OR: 15.8).

“The earlier participants were born, the higher the prevalence of strabismus and nystagmus in adulthood,” the researchers noted in their paper on the findings, published recently in the British Journal of Ophthalmology. They also pointed out, “This is one of the few studies reporting data for esotropia, exotropia, hypertropia/hypotropia and nystagmus separately with individual risk factors, demonstrating that esotropia is the most frequent type of strabismus followed by exotropia and hypertropia/hypotropia.”

Because the data also showed that strabismus often occurs during early childhood in individuals who were born preterm, there may be a need “to evaluate whether screening in this high-risk population for amblyopia should be recommended,” the authors suggested.