The mosquito-borne disease suspected of causing serious birth defects is expected to spread to all countries in the Americas except Canada and Chile and remains a global health emergency, according to the World Health Organization.

The mosquito-borne disease suspected of causing serious birth defects is expected to spread to all countries in the Americas except Canada and Chile, according to the World Health Organization.

The mosquito-borne disease suspected of causing serious birth defects is expected to spread to all countries in the Americas except Canada and Chile, according to the World Health Organization.

Some Brazilian babies born with birth defects linked to Zika virus also have severe eye problems in addition to brain damage, doctors reported Tuesday.

The doctors found eye damage in more than one-third of babies they studied in December at a hospital in Salvador, Brazil’s third-largest city. The babies all were born with a rare condition known as microcephaly, which results in head and brain abnormalities.

The findings, detailed Tuesday on the website of the journal JAMA Ophthalmology, provide the strongest evidence to date that the ­mosquito-borne virus is also linked to potentially threatening vision problems, researchers said.

[‘The risk to Puerto Rico is significant,’ CDC director says]

Lee Jampol, a professor of ophthalmology at Northwestern University’s Feinberg School of Medicine, said that lesions found in the babies’ retinas could have far-reaching effects for families trying to care for the infants and the next generation.

“We know these babies are at risk for real problems with their vision,” said Jampol, who also co-authored a commentary on the study. “The main message here is that it’s likely that Zika is going to spread further, and you’re going to have to pay attention to these babies,” he said in an interview.

Experts have raised the possibility that the virus is associated with other neurologic problems. Yale University epidemiologist Albert Ko, who is also researching the potential effects of the virus in Brazilian newborns, said researchers are also seeing some babies with microcephaly who have impaired hearing.

[Zika expert: ‘Microcephaly may be tip of the iceberg’]

In Brazil, the epicenter of the outbreak in the Americas, Zika has been linked to a surge of microcephaly cases. CDC officials have said the association between the virus and microcephaly has become stronger. So, too, has a link between Zika and Guillain-Barré syndrome, which can lead to paralysis in adults. Several South American countries have identified cases of that rare condition.

The JAMA study involved 29 infants and their mothers who were examined at Roberto Santos General Hospital in Salvador, Brazil. Twenty-three of the mothers said they suspected a Zika infection during pregnancy, most of them in the first trimester. Of the 29 infants born with microcephaly, 10 of them, or more than one-third, had “severe ocular abnormalities,” the study found.

The most common problem affected their retinas.

“Imagine you have a big TV screen,” said Rubens Belfort Jr., a study co-author, in an interview. “That’s the retina. In these babies born with microcephaly, many areas of the screen will never work because they have dark spots.”

Three D.C. residents caught the Zika virus while traveling in Latin America, including one pregnant woman. (WUSA9)

Some of the babies are still being cared for in intensive care units, said Belfort, a physician at the Federal University of Sao Paulo in Brazil. In one case, the mother was 16 and the father was 17. Their baby has microcephaly and severe damage to both retinas.

“The baby will probably be blind, maybe deaf, and have other cognitive issues,” Belfort said. “It’s a big problem. What is going to happen to the mother? The damage goes much beyond the eye or the child.”

[What is Zika and what are its risks as it spreads?]

Belfort and researchers found the linkage between the virus and eye damage in two earlier studies examining different populations of babies. The researchers have ruled out other possible causes of microcephaly, such as infections with rubella or toxoplasmosis.

The possibility of causes other than Zika for the microcephaly and eye damage are “very small,” Belfort said. “When you start to see the same changes in different populations, it makes it probable.”

In Brazil, researchers are planning to follow all the babies as they grow to monitor their vision. They also plan to examine more patients — babies with microcephaly and babies with normal-size heads — in other parts of Brazil’s northeast, hardest hit by the virus.