The Effect of Fixation Target on Fixation Preference Testing

Abstract

Purpose:

The purpose of this study is to determine whether the outcome of fixation preference testing in amblyopia is affected by the type of fixation target.

Methods:

Fifty patients with a history of amblyopia, either treated or untreated, and 30 normal patients were studied. Standard fixation preference testing was performed in patients with manifest strabismus of at least 10^Δ, and induced tropia testing with a 12^Δ vertical prism was used in all others. Each patient was tested with three different targets: a light, a wiggle-stick, and a large toy. Outcomes were compared to determine the agreement between the different targets and the sensitivity of each.

Results:

A high rate of sensitivity was achieved using each of the targets, regardless of the depth of amblyopia. The rates of exact agreement between the different targets were 66–78%. Close agreement was found in 80–86% of patients. The strength of fixation preference did not correlate with the magnitude of interocular acuity difference. Specificity in normal patients was 100% with all targets.

Discussion:

Sensitivity and specificity of fixation preference testing do not appear to be significantly influenced by the type of fixation target employed. Because fixation preference tends to be quite strong in amblyopia, regardless of the actual difference in interocular acuity, it may be a more reliable technique for diagnosis of amblyopia than for assessment of severity or monitoring of treatment.

• Amblyopia
• fixation preference
• induced tropia test