March 2010

 

CATARACT /IOL

 

Lens implantation in infants: how young is too young?


by Tony Realini, M.D.

 

 
Congenital nuclear cataract

Above infant, before surgery (Insert is opposite, normal eye) Source: JL Derner, Jules Stein Eye Institute

Visual outcomes in eyes with congenital cataract depend as much, or more, on optical correction as on surgical technique. Options for optical correction vary by age in the pediatric population. In children under the age of 12 months, optimal methods of post-op optical correction have yet to be established through evidence-based methods.

“Implantation of IOLs at the time of cataract surgery has become the standard of care for children over 12 months of age,” said Scott Lambert, M.D., professor of ophthalmology and pediatrics, Emory University, Atlanta. “There is general reluctance, however, to use IOLs in patients under the age of 12 months.”

Dr. Lambert is the principal investigator of an ongoing multicenter, randomized clinical trial comparing visual outcomes in children receiving primary IOL implantation versus contact lens use following cataract extraction in children less than one year of age. Until the trial is completed, the debate over primary IOLs versus contact lenses continues.

The case for IOLs

There are several important advantages to IOLs in this age group, Dr. Lambert said. “IOLs provide a guaranteed partial optical correction at all time,” he said. “In contrast, contact lenses only provide optical correction when they are worn, which isn’t 100% of the time. Thus, IOLs are likely to be associated with less amblyopia than contacts.”

Another advantage of IOLs over contacts is reduced aniseikonia. “IOLs more closely approximate the optics of the crystalline lens because they are placed in the same optical plane as the natural lens,” he said. “Aphakic contacts can induce from 12%-17% angular magnification, resulting in aniseikonia.”

Primary IOL implantation also increases the likelihood of in-the-bag IOL placement, Dr. Lambert said. “Most children left initially aphakic will eventually undergo secondary IOL placement. It is technically much easier to place the IOL in the capsular bag at the time of cataract removal than it is later on. Thus, fewer lenses will need to be placed in the sulcus, where decentration and uveal erosion can be complications.”

In addition, he asserted that pseudophakia saves time when compared to contacts. “All parents have to spend some time caring for their child’s contacts,” he said. “They can be difficult to insert and remove for cleaning purposes, and they are expensive to replace if needed. Also, contact lens wear is stressful for parents and requires constant vigilance to ensure that the lens is still in place and that there are no signs of infection.”

Finally, he said, “There is now a growing body of literature reporting favorable visual outcomes after IOL implantation in young children, suggesting that IOLs can be safely implanted in neonates.”

The case for contact lenses

Monte Del Monte, M.D., professor of ophthalmology and pediatrics, University of Michigan Kellogg Eye Center, Ann Arbor, Mich., prefers not to perform primary IOL implantation in children under one year of age.

“This approach has several disadvantages,” he said. “For instance, the eye undergoes rapid growth through 12 months of age. As it does so, it also undergoes a very large myopic shift during the same time frame. This poses important questions. What size IOL should be implanted in a growing eye? Implanting an IOL before 12 months of age requires us to pick an IOL for life in the setting of a rapidly growing eye.”

Dr. Del Monte expressed concern regarding the determination of IOL power. “What power IOL should be implanted? How should the power be determined? Most of the IOL power formulas produce fairly consistent powers in the range of normal axial lengths, but they can vary quite a bit in shorter eyes. So the choice of formulas for IOL calculations matters a great deal in these small eyes. A related question is this: What post-operative refraction should you aim for?” Current recommendations range anywhere from +2 D to +8 D, he said.

Dr. Del Monte tackles optical correction after congenital cataract surgery in this age group differently. “My preferred technique is an extracapsular cataract extraction with a posterior capsulotomy and an anterior vitrectomy,” he said. “I make the anterior capsulotomy approximately 5 mm in diameter and the posterior capsulotomy approximately 5-6 mm in diameter. Then we start contact lens therapy on the first post-operative day.” He reserves IOL implantation as a secondary procedure, which he carries out after the child has reached approximately 1 year of age.

There are several advantages of delayed IOL implantation over primary IOL implantation, he said. “You don’t need a perfect capsulorrhexis if you aren’t placing an implant at the time of surgery. There are fewer intraoperative and post-operative complications. Fewer patients need early reoperations. There are no secondary cataracts. And perhaps most importantly, it is quite easy to change power as the eye grows.”

Dr. Del Monte acknowledged a few downsides to his approach. “Aphakic contact lenses are expensive,” he said. “There is a higher risk of allergy and infection in contact lens wearers. Glaucoma is common in these eyes, and contact lens wear limits surgical options for glaucoma management—blebs are not a good idea in eyes that require contact lens correction.”

Despite these limitations, Dr. Del Monte feels that his approach is the best way to manage optical correction in young patients undergoing cataract surgery. “This approach provides optimal optical correction throughout this important period of eye growth and visual development that occurs between birth and age three,” he said.

Editors’ note: Drs. Lambert and Del Monte have no financial interests related to their comments.

Contact information

Del Monte: madm@umich.edu
Lambert: slamber@emory.edu

Lens implantation in infants: how young is too young? Lens implantation in infants: how young is too young?
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