Eyeworld

EW NEWS & OPINION 14 Surgical astigmatism may not need treatment in pediatric cases A stigmatic errors resulting from pediatric cataract surgery through a 6.5-mm limbal incision ultimately resolve within 3 months of surgery, according to Erick D. Bothun, M.D., assistant professor, University of Minnesota, Minneapo- lis. In the December 2010 e-edition of the Journal of the American Associa- tion of Pediatric Ophthalmology and Strabismus, investigators found that astigmatism typically returned to pre-op levels following large-incision cataract surgery. After large-incision cataract sur- gery, astigmatism is essentially uni- versal, finds Dr. Bothun. "It's typical that there's some degree of astigma- tism when we suture up a wound with multiple sutures," he said. "In addition to potentially creating some astigmatism, we're oftentimes working with some underlying astig- matism that the patient has, so after a large incision it's typical that we'll find some degree of it." Self-correcting astigmatism Typically astigmatism is something that is considered to be static in so- ciety. "Astigmatism in any individ- ual is usually corrected long term with spectacles or with certain re- fractive techniques," Dr. Bothun said. "Thus the understanding of what to do with astigmatism after cataract surgery is to treat it." Inves- tigators realized that in the pediatric literature as well as in their own practices, even for children with high degrees of post-op astigmatism, it would often go away. With this in mind, investigators decided to launch a retrospective study looking back at large-incision cataract cases involving children up to the age of 18. Included here was a total of 93 eyes of 72 children who underwent cataract extraction with IOL implantation through a 6.5-mm limbal incision. Large-incision lenses were placed in patients' eyes through 2002, at which point the practice started routinely using fold- able IOLs. "The age at which we're putting in an intraocular lens con- tinues to get lower and lower," Dr. Bothun said. "But primarily these lenses were placed in children be- yond age 1, typically age 2 through the teenage years." Investigators then compared pre-op astigmatism to post-op results at 3 months. They found that pre- op, the mean astigmatism was 1.2 D. Although on the first post-op day this had jumped to 6.6 D, by the 3- month post-op mark it had returned to 1.2 D. "The most significant result was that operatively induced astigma- tism typically resolved after cataract surgery in children," Dr. Bothun said. "That resolution typically took place in the first 3 months after sur- gery." Investigators found that the astigmatism that was left was consis- tent with the astigmatism that the patient had prior to the surgery. "The surgery is inducing some great degree of astigmatism, but it's resolv- ing over the first 3 months and going back to the pre-op findings," he said. This return to pre-op astigma- tism levels was seen in all of the children across the board. For the study, the children were divided into two groups—those younger than age 9 and those older than age 9 up through age 18. "The improvement in astigmatism was seen not only in the younger children but also in the teenagers," Dr. Bothun said. "We compared the younger and the older kids, and the younger kids had the same resolution as the older kids." Elastic sclera Dr. Bothun theorized that it is the forgiving nature of the sclera in chil- dren that makes the difference. "Children have more elastic sclera that stretches easier than that of adults," he said. "This is modeled the most in children with glau- coma—their eyes stretch out and get bigger over time." The same thing likely happens with sutures. "It is our understanding histologically that when we place a suture and cre- ate a tight spot that's perpendicular to the suture on the cornea and on the sclera, the stretching in that di- rection happens proportional to the tightness of the suture," Dr. Bothun said. "The tighter the suture, the tighter the sclera, and the more it stretches and evens out to the pre- operative status." Children's eyes respond differ- ently than those of adults. "We're getting a stretching of the sclera and a relaxing of the tissue tension at the suture site that is different than in adults," Dr. Bothun said. "In adults, we place a suture and create astigma- tism." Dr. Bothun hopes that practi- tioners come away from the study April 2011 by Maxine Lipner Senior EyeWorld Contributing Editor Through the eyes of a child: Post-op astigmatism resolves with time tail, but they couldn't examine vita- min C alone. This was the first trial that was able to look at vitamin C alone." Confounding variables While observational studies sug- gested possible benefits to vitamin supplementation, none was shown in this prospective, randomized trial. Dr. Christen is not surprised that outcomes here were different. "In observational studies, the problem is that people choose what treatments to take so there's a lot of potential for confounding," Dr. Christen said. "Those people who have healthier diets on average tend to have other lifestyle factors that are also health- ier, so it's tough to tease out. If people take in more fruits and veg- etables to get the high vitamin C, they're probably doing a lot of other things that decrease the risk of cataract." Although in observational stud- ies investigators try to control for such factors, this is not always possi- ble. "The benefit of a randomized trial is that because you randomly assign treatment, the two groups— the active and the placebo groups— tend to be virtually identical on all of the other potential risk factors," Dr. Christen said. "We really are ze- roing in on the effect of treatment in a randomized trial." Overall, despite the fact that in- vestigators concluded that there was no long-term benefit in vitamin E or vitamin C supplementation, Dr. Christen still encourages patients to consume a healthy diet. "There are many components of fruits and veg- etables," he said. While investigators try to zero in on specific nutrients such as E and C, there might be other components in the food itself that are at work. With this in mind, Dr. Christen stressed the importance of a healthy diet. "Healthy diet is still highly recommended," Dr. Christen said. EW Editors' note: Dr. Christen has no fi- nancial interests related to his com- ments. Contact information Christen: wchristen@rics.bhs.harvard.edu Cataract continued from page 13 In pediatric cases involving astigmatism resulting from large-incision cataract surgery, treatment may not be necessary Source: Erick D. Bothun, M.D. continued on page 16

• Cover