The Method of Treatment Cessation and Recurrence Rate of Amblyopia

Abstract

Background and purpose: To date, much of the research regarding amblyopia has been focused on which therapeutic modality is the most efficacious in amblyopia management. Unfortunately, there is a lack of research into which method of treatment cessation is the most appropriate once therapy has been completed. The purpose of this study is to investigate if the cessation method affects the recurrence rate of amblyopia. Methods: This study was a prospective randomized clinical trial of 20 subjects who were wearing full-time occlusion and were at the end point of their therapy. The subjects were randomized into one of two groups: abrupt cessation or therapy tapering. All subjects were followed for 3 consecutive 4-week intervals, for a total of 12 weeks, to assess the short-term recurrence rate of amblyopia. Subjects who were in the tapered group had their occlusion reduced from full-time occlusion (all waking hours minus one) to 50% of waking hours at study enrollment (i.e., from 12 hours/day to 6 hours per day); occlusion was reduced by an additional 50% at the first 4-week study visit (i.e., from 6 hours/day to 3 hours), with occlusion being discontinued completely at the week 8 visit. All subjects who were in the abrupt cessation group had their full-time occlusion discontinued completely at the start of the study (i.e., from 12 hours/day to none). Additional assessments were also conducted at week 26 and week 52 post–therapy cessation to determine the longer term amblyopia regression rate. For the purposes of this study, recurrence was defined as a 0.2 (10 letters) or more logarithm of the minimum angle of resolution (logMAR) loss of visual acuity. Results: A recurrence of amblyopia occurred in 4 of 17 (24%; CI 9%–47%) participants completing the study by the week 52 study end point. There were 2 subjects from each treatment group who demonstrated a study protocol–defined recurrence. Conclusion: There was a 24% risk of amblyopia recurrence if therapy was discontinued abruptly or tapered in 8 weeks. In this small sample, the assigned cessation method did not affect the rate of amblyopia recurrence. It is recognized that the smaller sample size in our study prevents us from making definitive conclusions on the potential role that abrupt cessation has on the regression rate of amblyopia. The sample size was too small to reach an acceptable level of statistical power; therefore the generalizability of the findings to the broad population of all patients with amblyopia requires continuing research. This study therefore could be considered as a pilot study.

ACKNOWLEDGMENTS

This principal work was carried out at the IWK Health Centre in affiliation with Dalhousie University. This work was presented in part at the XI International Orthoptic Congress, Antwerp, Belgium.

Declaration of interest: The authors of this study have no commercial relationships relevant to the article's subject matter.