Preterm Births Associated With Corneal Aberrations

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Researchers in Germany report that extreme prematurity itself—not necessarily the occurrence of retinopathy of prematurity (ROP)—is associated with increased higher-order aberrations of the cornea in former preterm infants.¹ These findings were unexpected, said lead author Achim Fieß, MD, at the University Medical Center in Mainz.

Study design. The prospective cross-sectional study compared the corneal shape of 226 former preterm infants, of a gestational age (GA) of ≤ 32 weeks, with 259 randomly selected children who had been born at full term (GA ≥ 37 weeks).

The researchers evaluated differ­ences in various corneal aberrations in relation to gestational age and ROP occurrence in these children. The various aberrations included astig­matism, coma, spherical aberration, and root-mean square of higher-order aberrations.

The subjects ranged in age from 4 to 10 years, an age group selected because little is known about the association between prematurity and altered cor­neal shape in early childhood, Dr. Fieß said. “We decided to investigate this age group to provide new insights for corneal aberration development in this decisive time frame of vision develop­ment.”

Dr. Fieß added that the study was possible only because of modalities, such as Scheimpflug imaging, which allows no-contact examination of the anterior segment. This is ideal for ob­serving children in detail.

Findings. In general, total corneal aberrations, both lower- and higher-order, increased as gestational age declined, with effects observed mainly on the anterior surface of the cornea.

Yet because infants on the older end of the preterm spectrum (GA of 29-32 weeks) had corneal aberrations com­parable to those children born at full term, the researchers refined the age parameters into moderate and extreme prematurity. It was extreme prematu­rity that was associated with increased higher-order and lower-order aberra­tions of the total cornea.

Clinical implications. While corneal aberrations may be one of several factors contributing to increased refractive error and low visual function, particu­larly in former extreme preterm infants, the visual effects of aberrations are expected to be small compared to myo pia or astigmatism, Dr. Fieß said. “Our finding, therefore, is less important for guiding treatment than it is for sug­gesting a further reason for low visual acuity and refractive error in former preterm children.”

Does the effect persist? Dr. Fieß is currently investigating the effect of low birth weight on ocular morphology in an adult cohort. This may determine whether corneal aberrations persist into adulthood in former preterm infants.

In the meantime, he said, “Our study highlights that, in particular, gestational age less than 29 weeks affects corneal shape. Extreme early prematurity is one decisive factor affecting corneal aberra­tions.”

—Miriam Karmel

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1 Fieß A et al. Invest Ophthalmol Vis Sci. 2017;58(14):6374-6378.

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Relevant financial disclosures—Dr. Fieß: None.

For full disclosures and the disclosure key, see below.

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