What's the best non-surgical treatment for exotropia?

Take home: Observation, patching, and the use of overminus lenses are three treatment approaches for intermittent exotropia; observation appears reasonable based on current research.

Observation appears to be a very reasonable option at this point for children with intermittent exotropia (IXT), said Jonathan M. Holmes, MD, Mayo Clinic, Rochester, Minn.

Dr. Holmes summarized recent research related to the non-surgical management of IXT including observation, patching, and overminus glasses.

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Dr. Holmes focused his analysis on larger and more recent trials and observational studies.

Regarding observation, Dr. Michael Clarke’s research group in England enrolled 460 children in a prospective study in which more than half of the children were only observed.¹

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“He found that 85% of children had no change in their level of control if just observed over a 2-year period,” Dr. Holmes said.

In patients only observed, the mean near stereoacuity improved, and the mean angle of deviation did not change. Less than one percent of patients in Dr. Clarke’s study developed constant IXT. However, there was one caveat: “This study was not population-based, and children were not randomized to their treatment assignment,” Dr. Holmes said.

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In a study led by Dr. Holmes² that included 95 children observed over two years, the rate of deterioration of near stereoacuity (three or more octave levels) was only 2% at year one and 7% at year two.

Importance of retesting stereoacuity

His study also revealed the importance of retesting stereoacuity. “After we thought they had deteriorated, the majority returned to baseline stereoacuity, stressing the need for a retest of stereoacuity when following children with IXT,” he said.

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Part-time patching is also a treatment option for IXT. Dr. Holmes presented information from a randomized trial led by the Pediatric Eye Disease Investigator Group (PEDIG)^3,4 where children ages 1 to 10 years old were randomized to observation including glasses or patching three hours a day.

The primary outcome was assessed at six months. The study found a low rate of deterioration in younger children (1 and 2 year olds) in both the observed group (4.6%) and the group with patching (2.2%).⁴ This difference was not statistically significant. In older children (3 to 10 years old), the deterioration rate was 6% in the group that was observed and 0.6% in the group with patching.³

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Although this was a larger difference, 4 of 10 deteriorations were questionable because three had started treatment prematurely and one of the patients who was deemed to have constant exotropia actually had excellent stereoacuity, suggesting the exotropia was not constant, Dr. Holmes said.

The PEDIG study was scheduled to reach a 3-year completion at the end of December 2015, so further results will be available soon, Dr. Holmes said.

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Another treatment option for IXT is overminus lens therapy, based on the idea of stimulating accommodation with additional minus power in the glasses, or allowing fusional vergence, with associated accommodation, where the overminus lenses allow clearer vision.

The PEDIG group recently finished a pilot study-as yet unpublished-that included children who were 3 to 7 years old. The children were randomized to overminus lenses versus observation. The observed children used plano glasses for masked assessment of outcome, if not prescribed non-overminus glasses at the start of the study.

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“We found that children assigned to overminus had better control at the end of the 8-week study, while wearing their glasses, than the observation group,” Dr. Holmes said.  A question from this study that remains unanswered is whether the overminus group children still have better control over the long term and particularly after treatment is discontinued.  A longer-term study is in the planning phase.

Unanswered questions

Questions that are still unanswered regarding IXT include whether long-term observation has any harmful effects, such as entrenched suppression and whether children with monofixational IXT behave differently and warrant a different approach. “It is also important to remember to assess the psychosocial effect of IXT in older children, and, if so, surgery rather than non-surgical management is very reasonable,” Dr. Holmes said.

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Dr. Holmes concluded that observation appears reasonable in many cases of childhood IXT based on current research. Part-time patching does not appear to have a great benefit and children dislike it, and overminus spectacle treatment may be helpful. Other nonsurgical treatments such as orthoptics and vision therapy are awaiting well-designed studies.

References

1. Buck D, Powell CJ, Sloper JJ, Taylor R, Tiffin P, Clarke MP. Improving Outcomes in Intermittent Exotropia (IOXT) Study group. Surgical intervention in childhood intermittent exotropia: current practice and clinical outcomes from an observational cohort study. Br J Ophthalmol. 2012;96:1291-5.

2. Holmes JM, Leske DA, et al. Stability of near stereoacuity in childhood intermittent exotropia. J AAPOS. 2011;15:462-467.

3. Pediatric Eye Disease Investigator Group, Cotter SA, Mohney BG, Chandler DL, Holmes JM et al. A randomized trial comparing part-time patching with observation for children 3 to 10 years of age with intermittent exotropia. Ophthalmology. 2014;121:2299-2310.

4. Pediatric Eye Disease Investigator Group, Mohney BG, Cotter SA, Chandler DL, Holmes JM, et al. A Randomized Trial Comparing Part-time Patching with Observation for Intermittent Exotropia in Children 12 to 35 Months of Age. Ophthalmology. 2015 122:1718-25.

Presentation title: Current Nonsurgical Treatment of Intermittent Exotropia

Jonathan M. Holmes, MD

E: holmes.jonathan@mayo.edu