Patients who underwent the therapy also had greater myopic shift compared to those that did not.
Pediatric patients who undergo overminus lens therapy for intermittent exotropia see some improvement in distance exotropia control, but they also experience greater myopic shift and the benefits of the therapy appear to go away once treatment is stopped.
Exotropia is a common form of strabismus in children; by some estimates it accounts for one quarter of all early childhood misalignment. While patients with the intermittent form of the disease experience normal alignment most of the time, the condition can result in long-term visual difficulties if left untreated.
A multicenter team of investigators, the Pediatric Eye Disease Investigator Group, wanted to figure out whether overminus lens therapy might be a sufficient therapy to spark long-term improvement and potentially avoid the need for corrective surgery. To find out, they launched a first-of-its-kind randomized clinical trial in patients with intermittent exotropia (IXT) between the ages of 3 and 10.
The trial involved patients at 56 clinical sites who were seen between 2017 - 2019. A total of 386 children were enrolled in the study, and each had a mean distance control score of 2 or worse and a refractive error of between 1.00 and -6.00 diopters. The primary outcomes were mean distance IXT control scores after 12 months of treatment, and scores at 18 months, which was 3 months after the end of treatment.
A total of 386 children were recruited into the study; 196 were put into an overminus therapy cohort and the remaining 190 patients were put in a non-treatment cohort. The patients were an average of 6.3 years old, and most (59%) were female.
The therapy initially showed benefits. At 12 months, the patients who had undergone the therapy had superior mean distance control compared to those without the therapy (1.8 vs 2.8 points, respectively, for an adjusted difference of -0.8).
Yet, the benefits of the therapy were short-lived. At 18 months, after the conclusion of therapy, the patients in the two groups had similar results. Those who had received the therapy had a mean distance control difference of 2.4 points, while those who did not receive overminus therapy had a difference of 2.7 points, for an adjusted difference of just -0.2 points.
Furthermore, myopic shift from baseline was greater in the overminus group than in the nonoverminus group after 12 months (-0.42 diopters vs -0.04 diopters, for an adjusted difference of -0.37 dipopters). Seventeen percent of the children in the overminus group had a shift of greater than 1.0 diopters, compared to just 2 patients (1%) in the nonoverminus group.
The investigators, including first author Angela M. Chen, OD, MS of the Southern California College of Optometry at Marshall B. Ketchum University, Fullerton, concluded that the therapy did not confer long-term benefits to patients.
“The beneficial effect of overminus lens therapy on distance exotropia was not maintained after treatment was tapered off for 3 months and children were examined 3 months later,” they concluded.
The study, “Overminus Lens Therapy for Children 3 to 10 Years of Age With Intermittent Exotropia,” was published online in JAMA Ophthalmology.