Brazil Zika Virus

Cassiana Severino holds her daughter, Melisa Vitoria, born with microcephaly, at the IMIP hospital in Recife, Pernambuco state, Brazil. Babies in Salvador, Brazil, were examined for eye abnormalities. (Felipe Dana/Associated Press)

Babies born with microcephaly in Brazil may have vision-threatening lesions in their eyes, say doctors investigating the country's Zika virus outbreak.

In Tuesday's issue of JAMA Ophthalmology, doctors describe eye abnormalities in 29 infants who were examined with their mothers at a hospital in Salvador, Brazil, in December 2015.

Of the mothers involved, 23 (79 per cent) reported suspected Zika virus signs and symptoms — including rash, fever, joint pain, headache and itch — during pregnancy, most of them during the first trimester.

"Findings from this case series demonstrate that 10 of 29 infants (34.5 per cent) born with presumed [Zika]-associated microcephaly have vision-threatening lesions," Dr. Rubens Belfort, Jr., of the Federal University of São Paulo, Brazil, and coauthors said.

In the study, doctors ruled out other infectious causes of microcephaly through clinical exams and blood tests. 

Studies are underway to test whether Zika virus infection causes microcephaly — for example, by comparing babies born to women who were infected with those born to women who weren't infected.

Dr. Lee Jampol and Dr. Debra Goldstein, of Northwestern University Feinberg School of Medicine in Chicago, wrote a journal commentary that accompanied the report.

They said the report implicates congenital Zika infection in "chorioretinal scarring" — the retina and membrane covering the white of the eyeball that supplies blood to the retina, Jampol and Goldstein said. 

The association between the increase in microcephaly, or small heads, and the Zika outbreak is still presumptive because blood tests for the virus weren't available in Brazil at the time of the outbreak. There could also be confusion with other causes of microcephaly, the commentators said.

They said eye lesions are presumptively associated with the virus.

"Based on current information, in our opinion, clinicians in areas where Zika virus is present should perform ophthalmologic examinations on all microcephalic babies," Jampol and Goldstein said. "Because it is still unclear whether the eye lesions occur in the absence of microcephaly, it is premature to suggest ophthalmic screening of all babies born in epidemic areas,".

When the West Nile virus first spread across the U.S., other retina issues were seen, they noted. The species of mosquito that spread West Nile In Canada was different from the one south of the border.