Early study results show no visual benefit for IOL implantation after congenital cataract removal

The study will follow patients for 5 years after initial cataract removal to compare primary with delayed IOL implantation.

M. Edward Wilson

Early results from a study testing IOLs in pediatric patients showed no difference in visual outcomes and a higher rate of complications among IOL recipients compared with patients who remained aphakic. However, study monitors advocated caution in attempting to interpret results.

In the multicenter Infant Aphakia Treatment Study (IATS), patients with unilateral congenital cataract were randomized to receive cataract surgery followed by either lens implantation or correction with contact lenses until a later date when an IOL would be implanted. The initial report of no difference in visual acuity is based on an analysis at 1 year of follow-up; the study is designed to follow patients for at least 5 years.

Primary IOL implantation may offer the potential of visual correction that more closely mimics the natural crystalline lens. Moreover, having at least some portion of the refractive correction constantly in place may be beneficial to amblyopia therapy, said M. Edward Wilson, MD, one of the members of the IATS steering committee.

“Now, it might be at the cost of a little more surgical trauma, but what we were investigating was if we implanted an IOL, will the vision be better, and if it is better, what is the price we are going to pay? And price not only in surgical trauma, but also in how well we could predict the growth of the eye,” Dr. Wilson said.

However, it is unknown whether primary implantation may be associated with a higher risk of postoperative complications that might offset any perceived benefit. Implantation of an IOL after congenital cataract has not been studied previously in a randomized, controlled, multicenter trial.

At 1 year follow-up from initial cataract surgery, grating visual acuity was 0.80 logMAR among the 57 patients in the group left aphakic and treated with a contact lens after cataract removal. Among the 57 patients who received a primary IOL implantation, visual acuity was 0.97 logMAR, but the difference was not statistically significant.

More reoperations

According to the study, after 1 year of follow-up, only 12% of patients in the contact lens group required reoperation for any reason, compared with 63% in the primary IOL group (P < .001).

“I’ve been careful to tell people that have asked me about the study that, because we’ve had many more returns to the operating room in the IOL arm, that people should use caution in recommending IOLs in the first 6 months of life until this study is completed,” Dr. Wilson said.

It is important to consider, he added, that the majority of reoperations in the IOL group constituted cleanup of fluffy material that most likely entered the visual axis after breaking off of a Soemmering’s ring. Additionally, Soemmering’s ring is more likely to form in infants, and so the study group may have been predisposed to potential complications.

During all cataract surgeries, attention was given to thorough cleanup of the capsular bag, and a posterior capsulorrhexis was formed in all cases, regardless of whether IOL implantation was to be primary or delayed.

“We know that even with meticulous cleaning, there are at least a few cells left. What they do is create new lens fibers, and we recognize that as Soemmering’s ring,” Dr. Wilson said.

Yet, the use of an IOL in young patients predisposed to Soemmering’s ring may be an additive risk factor in the formation of disturbances in the visual axis, thus necessitating a second operating room visit for cleanup.

“What we’ve discovered is that when you don’t put an IOL in, the anterior capsulorrhexis and the posterior capsulorrhexis seal, and they trap that Soemmering’s ring so it doesn’t really cause a problem. But the capsule sticks to itself better than it does to acrylic,” Dr. Wilson said.

As a result, Soemmering’s ring may be better trapped inside the capsule, as well as more easily removed, in aphakic patients at the time of secondary implantation. For patients in the primary IOL group, however, the proliferating material may escape to the pupillary space, necessitating an additional operation in some cases.

At the same time, the study is still in the early stages, and so interpretation may be unwarranted at this point and extrapolation not possible. After 5 years’ follow-up beyond the initial surgery, more accurate visual acuity testing can be performed and the breadth of complications in both groups can be ascertained.

“Despite those reoperations, the visual acuity is not worse, and the glaucoma risk so far is not worse,” Dr. Wilson said. “I think the returns to the operating room are a problem, but there are also some surgeons that say we need to follow them longer, because the aphakic patients are going to get a return to the operating room to get the implant put in sooner or later.” – by Bryan Bechtel

Reference:

• The Infant Aphakia Treatment Study Group. A randomized clinical trial comparing contact lens with intraocular lens correction of monocular aphakia during infancy: grating acuity and adverse events at age 1 year [published online ahead of print May 10, 2010]. Arch Ophthalmol. doi:10.1001/archophthalmol.2010.101.

• M. Edward Wilson, MD, can be reached at Storm Eye Institute, 167 Ashley Ave., Charleston, SC 29425; 843-792-7622; fax: 843-792-1166; e-mail: wilsonme@musc.edu.