Some Brazilian babies with Zika-related birth defects show eye problems

A study published Tuesday found that one-third of babies with a birth defect linked to the Zika virus also display eye abnormalities that could affect their vision.

The 29 babies in the study were born with microcephaly, a condition that results in abnormally small heads and incomplete brain development. Brazil noted a sharp increase in microcephaly cases about six months after the first reported cases of Zika in that country.

In the Jan. 30, 2016 photo, Solange Ferreira bathes her son Jose Wesley in a bucket at their house in Bonito, Pernambuco state, Brazil, 

Ten of the 29 infants showed eye abnormalities, according to the study, led by researchers at the Federal University of São Paulo in Brazil and published in JAMA Ophthalmology.

Nearly 80% of the babies' mothers reported suspected Zika symptoms while pregnant, including rash, fever, joint pain, headache and itch. Of those who reported illness, 78% experienced symptoms in the first three months of pregnancy, according to the study. Four of five people with Zika infections show no symptoms.

In an accompanying editorial, Lee Jampol and Debra Goldstein of Northwestern University's Feinberg School of Medicine suggest doctors perform thorough eye exams on all babies with microcephaly in areas with Zika outbreaks.

"We're very concerned about this," said Jampol, a professor of ophthalmology at Northwestern. "There hasn't been enough testing yet to know what these babies' vision is going to be."

Most of the babies eyes showed damage to the retina, the area in the back of the eye that receives images and sends signals to the brain about what is seen. One baby had a hole in the iris, the colored part of the eye, although it's not clear if that was coincidence or related to the microcephaly and Zika infection, Jampol said.

In addition to the eye abnormalities, the babies could suffer vision problems due to the brain damage caused by microcephaly, Jampol said.

"As more babies are examined, we'll have a better idea of the range of damage that occur to the retina," he said.

Although scientists can't definitively say prenatal Zika infections cause microcephaly, the World Health Organization says evidence suggests a strong association. Jampol said "it's very highly likely" that Zika caused the babies' eye problems.