Fixation Characteristics of Severe Amblyopia with Eccentric Fixation and Central Fixation Assessed by the MP-1 Microperimeter

Objectives: To investigate the fixation patterns in severe amblyopia with eccentric or central fixation by the MP-1 microperimeter. Design: Fixation test was performed on 38 patients with severe amblyopia using the MP-1 microperimeter, 20 patients with eccentric fixation (EF group), and 18 patients with central fixation (CF group). Fixation location and fixation stability were quantified by preferred fixation eccentricity and bivariate contour ellipse area (BCEA, deg(2)) respectively. Comparisons of BCEA between amblyopic and fellow eyes (FE) in both groups and between amblyopic eyes (AE) in both groups were analyzed. Linear regression analysis was used to investigate the risk factors for fixation instability in patients with eccentric fixation. Results: In EF group, the BCEA of AE was 14.68 +/- 19.21 deg(2), which was significantly larger than that of FE (1.294 +/- 1.840, F = 9.243, p = .007). Linear regression analysis showed that only preferred fixation eccentricity (beta = 6.536, 95% CI: 2.665 similar to 10.406, p < .005) was correlated with BCEA of AE. The BCEA of AE in the EF group was significantly larger than that of AE in the CF group (4.95 +/- 3.44 deg(2), t = 2.227,p < .05), although the BCVA was not significantly different between two groups (t = 0.129, p = .898). Conclusions: The fixation ability in amblyopia with eccentric fixation was found to be significantly worse than those with central fixation and preferred fixation eccentricity was the only predictor for the instability. MP-1 is an effective tool to quantify fixation features for diagnosis and follow-up of eccentric amblyopia patients.