July 2009

 

CATARACT/ IOL

 

Early surgery bodes best for bilateral congenital cataracts


by Maxine Lipner Senior EyeWorld Contributing Editor

 

 

Investigators peg 14 weeks as the critical period

Congenital cataract

For children with congenital bilateral cataracts, surgery within the first few weeks of life results in significantly better visual acuity than in cases where removal is delayed even slightly, according to Eileen E. Birch, Ph.D., senior research scientist, University of Texas Southwestern Medical School, Dallas. In the article published in the February 2009 issue of the Journal of the American Association for Pediatric Ophthalmology and Strabismus, investigators set out to determine what the optimum timing was for dense bilateral cataract removal in congenital cases.

Typically babies are screened for cataracts in the newborn nursery. While there’s a set protocol for unilateral cases, for bilateral patients there has been no clear-cut consensus on when to time the surgery. “Unilateral cataracts are considered almost an emergency situation, and babies will often have their surgery at two weeks of age,” Dr. Birch said. “For the bilateral cataracts we didn’t have a lot of information before this. Textbooks say to have the surgery by three months of age at the latest.” After that, experts find that vision diminishes drastically.

Studying bilateral cases

Dr. Birch was among those who helped to set the standards in unilateral cases. “Starting in 1985 we were studying unilateral cataracts,” she said. “I spent quite a lot of years figuring out what the optimal treatment protocol is for them.” In such cases Dr. Birch found that surgery by six weeks of age provided patients with good useful vision of 20/40 to 20/60. However, data on what to do about bilateral cataracts has been scarce. “Most of the studies that have been done, and there have been very few, show that there really was not an age effect. Most children with bilateral cataracts get a 20/60 or 20/80 level of vision regardless of when they undergo the surgery up to one year of age,” Dr. Birch said. Since there were few reports about the outcomes following early surgery, Dr. Birch and fellow investigators decided to concentrate their efforts there. “We thought we could focus on those kids who had their surgery in the first 10 weeks of life and see if there was an age effect that might improve on the 20/60 to 20/80 outcome,” she said.

The study of 37 infants with dense bilateral cataracts included 14 who underwent surgery by four weeks of age. Some of the 23 remaining children had surgery as late as 30 weeks of age. To gauge results, investigators used several models. “One model was that there’s no effect of age of surgery,” Dr. Birch said. “Another was that any delay in surgery gives you a progressively worse outcome.”

Investigators also considered that there might be a critical age after which the outcome depends upon the extent of the delay or that there might be a latency period before the period of delay that would become critical.

Early surgery urgent

Results appeared to resemble the second medical model. “We found that in the first 14 weeks of life there was a progressively worse outcome the longer the delay,” Dr. Birch said. “Results showed that the child lost one line of visual acuity for every three weeks that the surgery was delayed in the first 14 weeks of life.” However, this 14-week period appeared to be a dividing line. “Once we got beyond 14 weeks everyone had about the same acuity,” Dr. Birch said. She acknowledges, however, that there were no late surgeries beyond 30 weeks included here.

Although there is some animal data suggesting that very early deprivation for brief periods can have a profound and long lasting effect on vision, these findings were still a little unexpected. “I was thinking that there might be an early window,” Dr. Birch said. “I thought there would be a period like we found for unilateral cataracts where maybe for the first four to six weeks it wouldn’t matter when you did the surgery, but we didn’t find that.”

The early surgery did come with a price, however. Investigators found that children did experience more complications. “There were more children who developed glaucoma and secondary membranes and ended up having more surgery for those,” Dr. Birch said. “But in the end they still had good visual outcomes.”

Dr. Birch hopes that practitioners can take away from the work a better understanding of when to perform surgery in these bilateral congenital cases. “The best long-term visual acuity outcomes occurred when surgery was performed during the first four weeks of life,” she said. “So our conclusion was that you can minimize the deprivation amblyopia. Although you do increase the risk for some complications, they are treatable and the children had good vision outcomes.”

Going forward Dr. Birch thinks a larger study may be warranted. “This was an initial study of 37 children,” she said. “We may find subtle differences within the first 14 weeks of life when we have more children.” She continues to conduct studies on this and thinks that there might be more to come. “There may be an early grace period in those first couple of weeks of life that we haven’t discovered yet,” she said.

Editors’ note: Dr. Birch has no financial interests related to her comments.

Contact information

Birch: 214-363-3911, birch@retinafoundation.org

Early surgery bodes best for bilateral congenital cataracts Early surgery bodes best for bilateral congenital cataracts
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