March 2008




Optical outcomes for babies

by Maxine Lipner Senior EyeWorld Contributing Editor



What to look for in determining how premature babies will likely fare

To most reliably predict visual potential in low birth weight babies, several exams are often needed Source: National Eye Institute

For low birth weight babies relying on a single exam alone can be a mistake when trying to predict visual potential, recent study results published in December 2007 issue of the Journal of American Association for Pediatric Ophthalmology and Strabismus indicate. With several exams practitioners can get a much better picture.

Low birth weight limbo

While low birth weight babies are a lot more inclined to have visual difficulties, for those without apparent clues such as severe retinopathy of prematurity (ROP) or retinal detachment it can sometimes be difficult to predict how they will ultimately do, according to Anna R. O’Connor, Ph.D., lecturer, University of Liverpool, Liverpool, England. “One of the reasons we particularly wanted to look at these extremely low birth weight children is because they have such a wide range of visual outcomes,” Dr. O’Connor said. She recently launched the study while at the Retina Foundation in Dallas, Texas, where they have an ongoing project looking at low birth weight children.

“We might not be able to change their outcome but parents want to know as much information as they can,” Dr. O’Connor said. “When they are so young, to be able to say that they’re going to have a long term deficit or that there’s a good chance that they will improve with time, I think that that is valuable information for parents.”

While of course a condition such as severe ROP portends poorly for an infant, if a low birth weight child is free of this disease or has a mild case it does not necessarily put him or her in the clear. “ROP is only the second most frequent cause of visual impairment in the extreme low birth weight child,” Dr. O’Connor said. “The first is neurological.” When the visual condition is the result of a neurological problem the long term impact isn’t always immediately apparent. For such conditions it has been necessary to often wait until the child is older to determine the severity of the problem, according to Dr. O’Connor.

Several exams needed

In the recent prospective, longitudinal study, investigators concentrated on 139 children who weighed less than 1,000 grams at birth, and who was currently over the age of three. For these children investigators had both early and later information Dr. O’Connor explained. When investigators reviewed the data they found that one measurement was not enough to predict visual outcomes—rather it was more important to look at the pattern that emerged over the course of several months. “It’s more important to assess these children on a couple of visits when they’re young and that gives you a lot more information than just one visit on its own,” Dr. O’Connor said. It is the rate of development as calculated by the slope of the early visual acuity measurements that is most predictive of a poor late visual acuity outcome. “If the slope was abnormal then there’s a 5.5 times greater risk of having an abnormal outcome in the long term,” Dr. O’Connor said. One measurement alone wasn’t enough to be useful to practitioners or to parents. “We have normative data for these (visual) tests, but there’s such a wide range of what is normal in these children who are born prematurely that they can just come out in the normal range somewhere, even if it might be low down,” she said. “So, one measurement is just not very informative.”

However, if several measurements were taken then looking at the slope of the development as plotted on a graph was far more helpful. “If the slope of change is relatively flat then that’s a very poor prognostic factor for the long term,” Dr. O’Connor said. “Whereas, if the child has a sharp development then that’s sort of in line compared to normal—that’s a very good prognostic factor for their long term outcome.” Dr. O’Connor was a bit surprised that the severity of specific visual conditions didn’t play a greater role. “We thought that the severity of the ROP condition might be the most indicative factor of their long term outcome, but it wasn’t,” she said. “It was interesting to see how strong a predictor looking at the slope of development actually was.”

Being able to offer families an indication of how severely their child’s vision may be affected is important for maximizing vision, believes Dr. O’Connor. “With a lot of these cases getting the information early can help to put in place support services,” she said. “A lot of these children are not going to have normal vision, but if they can get the right glasses and the right treatment we can help them to maximize what they’ve got.” For example, such children can be given low visual aids such as magnifying glasses if appropriate, according to Dr. O’Connor. Also, if it is apparent that a child is likely to have very low vision, they can be taught Braille at an early age when they are more apt to pick it up rapidly.

Predicting how these young patients are going to fare is only going to become more important with time, Dr. O’Connor believes. “This is a population that is not going to go away—they’re survival rates are increasing,” she said. “So, this is something that we need to take particular care over.”

Editors’ note: Dr. O’Connor has no related financial interests related to his comments.


O’Connor: 44-151-794-5733,

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