Atropine treatment of amblyopia: is a swap in fixation necessary?

To investigate the impact of fixation on vision outcomes in patients with amblyopia undergoing atropine treatment and the validity of the "cyclo-swap test" (CST) as a method of predicting atropine efficacy.

Sixteen children with amblyopia were included. The initial examination included a vision assessment and CST, in which fixation was assessed at 1/3 m, 6 m, and at distances less than 1/3 m. Children were treated for 10 weeks and reviewed at 5-week intervals with cessation of atropine 4 days prior. Vision and fixation were assessed at the follow-up visits. Children demonstrating no fixation swap initially were additionally observed after 1 week of atropine treatment under maximum cycloplegia.

Eight children demonstrated a fixation swap (FS group) to the amblyopic eye during the CST at either 1/3 or 6 m, and 8 demonstrated no fixation swap (NFS group). By the end of the 10-week treatment period, both groups demonstrated a mean visual acuity improvement of between 2 and 3 lines (FS = 0.22 log units; NFS = 0.27 log units). Six of the 8 children in the NFS group demonstrated improvement in vision, all of whom also demonstrated a fixation swap at some stage.

Vision improvement in patients using atropine is likely to be attributable to a fixation swap that occurs during the treatment phase. The CST performed at 1/3 and 6 m has little value in predicting improvements in vision; however, when performed at distances of less than 1/3 m, it may provide valuable clinical information about atropine efficacy.