A previously speculated, yet unproven risk factor was demonstrated in the first large randomized clinical trial to examine the safety and efficacy of overminus therapy for intermittent exotropia (IXT). While children achieved significantly improved distance control during a 12-month period, an important myopic shift occurred in the treatment group, according to the JAMA Ophthalmology study. In fact, after 12 months of overminus therapy, the risk of greater than 1.00 D myopic change was almost 15 times that of the control group, the study reported. 

Researchers enrolled 386 children, (3 years to 10 years old, mean age 6.3 years), with IXT, moderate or poor distance control, and cycloplegic spherical equivalent refractive error of -6.00 D to +1.00 D. Participants were enrolled at 56 community- and academic-based clinical sites affiliated with the Pediatric Eye Disease Investigator Group (PEDIG), from January 2017 to January 2019. Participants were randomized 1:1 into overminus treatment and control groups and masked to their assignment.

Children in both groups were asked to wear their eyeglasses full-time. Those who received overminus therapy wore spectacles for 12 months at -2.50 D added to their spherical power, and from 12 months to 15 months, lenses at -1.25 D over the refractive error. In months 15 to 18, they returned to nonoverminus lenses. Participants in the control group wore eyeglasses reflecting their cycloplegic refraction and corrected for astigmatism during the total 18-month period. 


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Their mean distance control improved decidedly and was stable through 12 months of overminus therapy (P <.001), however after tapering from month 12 to 15 and wearing their regular spectacle prescription for 3 months, distance control did not persist and investigators reported no statistical significance at 18 months between the treatment and control groups (P =.09).

Further, while 2 of the 169 control patients(1%) displayed risk for >1.00 D of myopic change, 33 of 189 therapy group participants (17%) showed the same risk, resulting in a “risk ratio of 14.8.” The risk was especially evident for children who exhibited myopia at baseline. An independent data and safety monitoring committee became concerned, and overminus therapy was concluded early. For 331 subjects who finished their 18-month follow-up visit, 292 completed all parts of the study. 

At follow-ups, clinicians masked to group assignment performed a near stereoacuity test, IXT control assessments, cover-uncover test, and the prism and alternate cover test (PACT). Parents reported the percentage of time lenses were worn, and parents and children filled out symptom and quality of life surveys. After 12 months, IXT symptoms were similar between the two groups, with the exception that 71 of 189 (38%) children receiving therapy indicated “their eyes hurt sometimes or always,” compared with 37 of 169 (22%) control participants. 

In the control group, 11% of participants were lost to follow-up, compared with 4% in the therapy set, representing a limitation of this study. Additionally, in real-world practice, overminus lenses are typically a temporary therapy, with a slower, more gradual tapering-off, such as in 0.50 D steps, progressing when satisfactory control is shown. Still, these data point to a raised risk of myopic change during the therapy for which clinicians and parents may want to take into account as they consider overminus to better align children’s eyes.

Reference

Chen AM, Erzurum SA, Chandler DL, et al. Overminus lens therapy for children 3 to 10 years of age with intermittent exotropia: a randomized clinical trialJAMA Ophthalmol. Published online March 4, 2021. doi:10.1001/jamaophthalmol.2021.0082