Detecting "lazy eye" earlier
Device identifies vision loss in children as young as 2, when it’s most treatable
July 7, 2011
Boston, Mass.--A simple, seconds-long screening exam with a handheld scanning device may enable pediatricians to identify “lazy eye,” a loss of vision in a structurally normal eye, in children as young as 2, report ophthalmologists at Children's Hospital Boston, who tested the device in 202 children.
Lazy eye or amblyopia, affecting 3 to 5 percent of all children, is the leading cause of vision loss in childhood. But it can be hard to detect in young children, who are the most responsive to treatment, because they cannot reliably communicate what they’re seeing or read eye charts.
"The eyes of a child with amblyopia can look perfectly fine, even while one eye is slowly losing vision," says senior author David Hunter, MD, chief of ophthalmology at Children's Hospital Boston. "Once a child reaches school age, treatment is less likely to restore useful vision. We'd really like to begin treating them when they're three years old - or younger."
Amblyopia usually results from a misalignment of the eyes (strabismus) or one eye having a weaker focusing power (anisometropia). In both cases, one eye is underused, and vision deteriorates as the brain loses its ability to interpret visual information from that eye. If the problem is detected early, ideally before age 4 or 5, doctors can reverse it by patching the stronger eye or blurring it with eyedrops, forcing the child to use the weaker eye.
Clinical testing of a prototype of the device, known as the Pediatric Vision Scanner, is described in the July 7 issue of the journal Investigative Ophthalmology and Visual Science. As children look at a blinking red light, a low-power laser scans their eyes to measure their alignment (known as binocularity), taking five readings over 2.5 seconds.
Hunter and colleagues tried out the scanner in 154 patients at Children's ophthalmology clinic and 48 children with normal vision, aged 2 to 18. Children with readily identifiable strabismus, other eye disease or developmental delay were excluded.
A binocularity score below 60 percent (fewer than three focusing successes in five attempts) was considered a “refer,” indicating a need for further examination. Among 2-to 6-year-old children, binocularity scores averaged 9 percent for those with amblyopia and 8 percent for those with strabismus, versus 89 percent in the control group. The scanner could detect amblyopia even in the absence of measurable strabismus, and documented improved binocularity in these children after treatment.
“We designed the device to detect strabismus, but the fact that the device could detect any form of amblyopia was completely unexpected – and a key advance for making more accurate referrals,” says Hunter, also a professor of ophthalmology at Harvard Medical School.
Overall, the scanner had an overall sensitivity and specificity of 96 percent for detecting amblyopia or strabismus as compared with gold-standard ophthalmologic tests. Hunter hopes the device will be adopted into general pediatric practice and used to screen toddlers and preschoolers for amblyopia during annual well-child visits. Eye exams done just before entry to school, mandated in some states, come too late to treat amblyopia most effectively, he says.
“This technology has the potential to give pediatricians the tool they need to quickly and easily identify those kids most in need of a specialist eye exam as soon as they develop a problem,” Hunter says. “As a result, we expect that health insurers and government agencies will embrace this test, which should reduce the cost of care while at the same time improving quality and efficiency, potentially saving vision in hundreds of thousands of children.”
The scanner is the result of 20 years of research funding from a variety of agencies. A lighter, more user-friendly prototype of the device is currently undergoing clinical testing at several independent centers.
Research fellow Sjoukje Loudon, MD, was first author on the paper, along with co-authors Caitlin Rook, CO, Deborah Nassif, PhD, and Nadya Piskun, PhD. The device was developed with the help of David L. Guyton, MD, and Boris I. Gramatikov, PhD, of Johns Hopkins University, and Robert Winsor, MSEE and Knute Ray, BS, formerly of the Space Telescope Science Institute.
[NOTES TO REPORTERS: Patients and video are available: http://www.youtube.com/watch?v=Zc_Yi4R0WsU]
Children’s Hospital Boston is home to the world’s largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 1,100 scientists, including nine members of the National Academy of Sciences, 11 members of the Institute of Medicine and nine members of the Howard Hughes MedicalInstitute comprise Children’s research community. Founded as a 20-bed hospital for children, Children’s Hospital Boston today is a 396 bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children’s also is the primary pediatric teaching affiliate of Harvard Medical School. For more information about research and clinical innovation at Children’s, visit: http://vectorblog.org.
- ### -