Limits and possibilities of the Lang stereotest

Abstract

Background: The Lang stereotest is a popular stereotest, which is frequently applied as a screening tool. It is easy to use, even in toddlers. Nevertheless, in clinical practice it is not always clear how the results should most appropriately be documented or interpreted. Specially for ruling out (micro)strabismus and/or amblyopia, it seems to be relevant to examine the state of knowledge regarding the limits and possibilities of the Lang stereotest more precisely. Material and methods: A literature search was conducted to collect and present the results of studies on the measurement accuracy and feasibility of the Lang stereotest in healthy subjects, in patients with strabismus and amblyopia. Results: Although the level of evidence is low, the results of some studies confirmed that neither Lang I nor Lang II are suitable for ruling out (micro)strabismus and/or amblyopia. Up to 36% of the children with (micro)strabismus achieved a positive result with Lang I. In subjects with amblyopia ex anisometropia, even 20–75% achieved a positive test result. The depth of the amblyopia seems to be responsible for this range. Conclusion: The Lang stereotest has undeniable advantages, especially in infants and toddlers. In particular, for this easy test it is necessary to critically interpret the answers. Simply pointing at the pictures may not be interpreted as a positive test answer. The implemented studies confirmed the Lang stereotest to be a suitable supplementary tool but using the Lang stereotest as a single screening tool never enables strabismus and/or amblyopia to be ruled out.