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Macula, optic nerve defects common in congenital Zika syndrome
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All infants with suspected congenital Zika syndrome have been found to have vision impairment, S. Grace Prakalapakorn, MD, PhD, assistant professor of ophthalmology and pediatrics at Duke University, said during the Zika Virus and Your Eyes webinar hosted by Prevent Blindness.
“Zika virus infection during pregnancy and its effects are historic,” Emily Petersen, MD, Pregnancy and Birth Defects Task Force at the CDC, said in her overview of the virus. “Never before in history has there been a situation where a bite from a mosquito could result in a devastating malformation.”
Zika overview
Petersen said that the last infectious pathogen that caused an epidemic of congenital defects was rubella, more than 50 years ago.
Currently in the U.S., there are 2,200 pregnancies with possible Zika virus infection. Ninety-eight infants have been born with a birth defect potentially related to congenital Zika virus infection, and eight births have been lost, she said.
The CDC collaborates with state, local and tribal health registries, the U.S. Zika Pregnancy Registry and U.S. Zika Active Pregnancy Surveillance System to understand the magnitude of infection. In the U.S. territories and freely associated states there are more than 4,500 pregnancies with possible Zika infection.
Zika is a signal-stranded RNA virus and is closely related to dengue, yellow fever, Japanese encephalitis and West Nile viruses, Petersen said.
Many people are asymptomatic. When symptoms do occur, Zika virus clinical disease is usually mild and includes fever, rash, joint pain, conjunctivitis and other symptoms such as headache and muscle pain, with symptoms lasting from several days to a week. Severe disease is uncommon, and fatalities are rare.
However, Petersen emphasized that there are serious implications for Zika virus infection during pregnancy.
The CDC recommends that pregnant women should not travel to areas with a risk of Zika.
“If a woman must travel, she should talk to her health care provider beforehand and take strict steps to prevent mosquito bites and prevent sexual transmission and talk with a health care provider afterward, even if asymptomatic,” Petersen explained.
Currently, there is no evidence to suggest that past Zika virus infection poses an increased risk of birth defect for future pregnancies once the virus has cleared the body, she added.
Petersen recommends Zika Care Connect, a resource from the CDC and the March of Dimes.
The site includes tools for women affected by Zika to identify qualified providers, and for providers it houses professional resources from the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists.
Ocular effects in infants
A few studies have evaluated the visual function among cohorts of infants with microcephaly due to suspected congenital Zika syndrome, Prakalapakorn said. Most ocular abnormalities occur in infants with microcephaly, but the abnormalities have also been identified in those without microcephaly in the anterior and posterior parts of the eye, she said.
While 40% exhibited ocular abnormalities, 100% of the children tested had vision impairment.
Cortical visual impairment might be the most common cause of blindness among children with congenital Zika syndrome, she added.
“Cortical visual impairment is a decreased visual response due to a neurological problem affecting the visual part of the brain,” Prakalapakorn said. “Among infants with microcephaly and presumed congenital Zika virus infection, the most commonly found structural ocular abnormality involves the macula and optic nerve.”
In macula findings, macular mottling, loss of foveal light reflex and chorioretinal atrophy is common. Optic nerve hypoplasia, optic nerve cupping and optic nerve pallor are common signs of damage to the nerve, she continued.
Other findings include retinal lesions, subretinal hemorrhage, pigmentary clumping, vascular tortuosity, congenital glaucoma, cloudy corneas, microphthalmia, cataract, strabismus, intraocular calcification, involuntary eye movement and displacement of the lens.
“To date, no active inflammatory lesions have been reported in infants with congenital Zika infection, whereas they have been reported in other diseases,” Prakalapakorn said.
Ocular manifestations and severity of findings vary among infant patients.
Currently the CDC recommends evaluating before discharge any infants whose mothers have risk factors for maternal Zika virus infection, traveled to or reside in an area of Zika virus transmission, had sex with a partner who traveled to or resided in such an area, for which maternal test results are not available, and where there is concern about infant follow-up.
“All infants with laboratory evidence of congenital Zika or with abnormal findings consistent with congenital Zika syndrome should be seen before 1 month of age,” Prakalapakorn said. “If the ophthalmologic exam before 1 month of life is normal, another complete exam is recommended at 3 months of age.”
Examining an infant at risk
The initial ocular exam should include visual acuity assessment, IOP measurement, slit lamp and dilated fundus examination.
She recommends the wince-to-light test and fix-and-follow tests in pre-verbal children. For those younger than 3 months of age, the wince-to-light test can be done, even on closed eyelids with a strong light, such as a pen light, she said.
Children who experience vision impairment or loss should be referred to a low vision specialist and development services early in life for early intervention, “to help babies improve and maximize their abilities,” Prakalapakorn concluded. – by Abigail Sutton
Reference:
Anderko L, et al. Zika virus and your eyes [webinar]. October 18, 2017. https://cc.readytalk.com/cc/s/meetingArchive?eventId=s8z4xbhhsn2h. Accessed October 18, 2017.
Disclosures: Petersen is an employee with the CDC. Prakalapakorn reports no relevant financial disclosures.