Liz Szabo

USA TODAY

A small study suggests that the range of serious eye problems in babies affected by the Zika virus is more extensive than previously known.

The study focused on three Brazilian baby boys with microcephaly, a condition in which infants are born with abnormally small heads and, in most cases, incomplete brain development. All three had eye problems that could impair their vision, and all of their mothers had suspected Zika virus infections during the first trimester of pregnancy, according to the study, published online Wednesday in Ophthalmology.

Doctors found three types of eye problems not seen before: bleeding in the retina, the area in the back of the eye that receives images and sends signals to the brain; missing blood vessels in the retina, where cells may have died; and torpedo-shaped lesions in the macula, the central part of the retina,

Doctors will need to follow the babies closely, because these conditions can lead to blindness, said Darius Moshfeghi, the study's senior author and a professor of ophthalmology at the Stanford University of School of Medicine.

Earlier studies of Brazilian babies also found abnormalities in the optic nerve, which brings visual information from the retina to the brain, as well as withering of the retina and the choroid, a blood vessel-rich part of the eye that brings oxygen and nutrients to the retina. A February study, published in JAMA Ophthalmology, found that 10 of 29 Brazilian babies with microcephaly had eye problems.

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

Doctors don't know exactly what caused the babies' eye problems. It's possible that the damage was caused by the microcephaly, which is linked to a variety of eye problems, said Moshfeghi, who co-wrote the study with researchers from Sao Paolo, Brazil.

It's also possible that the Zika virus, which is known to target the fetal brain, attacked these infants' eyes, Moshfeghi said.

Until doctors learn more, ophthalmologists should examine all babies with microcephaly who are born in areas with Zika outbreaks, Moshfeghi said. Doctors don't yet know if Zika can cause eye problems in babies without microcephaly.

The new study could help doctors caring for babies affected by the Zika virus, said pediatric ophthalmologist Michael Repka, a spokesman for the American Academy of Ophthalmology and a professor of ophthalmology at Johns Hopkins University. The number of babies with Zika-related eye problems is likely to increase as the outbreak spreads, he said.

The American Academy of Ophthalmology plans to update its statement on caring for patients with the Zika virus based on this study.

At least 544 Americans in the continental U.S. have been infected with Zika, including 157 pregnant women. All of the cases were related to travel, according to the Centers for Disease Control and Prevention.

More than 830 cases of Zika have been diagnosed in U.S. territories, where Zika is spreading among local mosquitoes. Those cases include 122 pregnant women, according to the CDC.