Abstract
Purpose :
There are no reported studies investigating fixation stability before and after amblyopia therapy. The purpose of this study was to determine if fixation stability improved in patients with amblyopia who had standard amblyopia therapy resulting in an improvement in acuity.
Methods :
Eight adult patients (age range 18 – 60; average 34.5 ± 16.66) with amblyopia (BCVA 20/40 or worse) due to anisometropia (N = 3) or anisometropia and strabismus (N = 5) were enrolled in the study. The patients received a comprehensive eye examination and wore their best correction for at least four weeks prior to baseline testing. They were instructed to patch their non-amblyopic eye for 2 hours per day (5 days per week). While patching, they were to perform near training exercises on the Amblyopia iNET program for 30 minutes and do any near work for the remaining 1.5 hours. The patients had a baseline amblyopia evaluation and came in for 12 weekly study visits, at which time their visual acuity was measured with the E-ETDRS protocol. At 12 weeks, the treatment was tapered off over one month and the patients came in for a final amblyopia evaluation at 24 weeks. Fixation stability was determined for the amblyopic eye with the Tobii TX300 eye tracker at baseline and week 24. The patients monocularly fixated the center of an “X” (2o vertical height) for 60 seconds. The bivariate contour ellipse area (BCEA in deg2 = πχ2σxσy(1-ρ2)1/2) was determined for 10 seconds of the fixation data beginning at 1 second after the trial start. The Chi-square value (χ2) corresponded to a probability of 0.95.
Results :
The amblyopia therapy resulted in a significant improvement in visual acuity (0.51 logMAR to 0.35 logMAR; paired t-test, p = 0.016). The average acuity improvement for the 8 patients over the 24 weeks was 8 letters or 1.6 logMAR lines. The averaged (SD) BCEAs at baseline and week 24 for all of the patients approached a significant level (p = 0.072, t = 2.12; 6.02 ± 3.96 and 3.00 ± 1.90, respectively). The average vertical variability of the ellipse decreased from baseline to week 24 (p = 0.01, t = 3.30) but the horizontal variability did not (p = 0.15, t = 1.63).
Conclusions :
The amblyopia therapy resulted in a statistically significant improvement in the visual acuity but the change in the BCEA only approached significance. However, the variability in the vertical direction of the ellipse decreased suggesting an improvement in fixation stability.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.