Name

Étude de la fiabilité du test de LANG sur une population de 604 enfants d’âge préscolaire

The LANG stereoscopic test allows the control of stereoscopic vision in young children. It is based on the process of random points and cylindrical images. Stereoscopy is theoretically absent or reduced in strabismus and amblyopia. The exploration of stereoscopic vision would therefore make it possible to reveal visual defects such as significant refractive disorders: anisometropia, strabismus, organic or functional amblyopia. The aim of this work is to make our contribution to these data by studying the intrinsic and extrinsic validity of the LANG I and LANG II stereoscopic tests.

The study concerns a population of 604 children aged between 3 and 5 years old. The examinations were carried out in a nursery by trained professionals : 

- Subjective examination : visual acuity - Lang I and Lang II.

- Objective examination : cover-test - Automatic refractometry under cyclopentolate 0.50% Biomicroscopic and fundus examination.

Automatic refractometry has been selected as the Gold Standard for the analysis of the diagnostic characteristics of the LANG I and LANG II stereoscopic tests. We retained as negative test when the child gave two correct answers for LANG I and three correct answers for LANG II (the star is a monocular image). Anisometropia greater than 1 diopter is considered significant.

- The prevalence of spherical and/or cylindrical anisometropia is 7.6% or 46 children out of 604 children

- The sensitivity (Se) is 23.9% for LANG I and 21.7% for LANG II

- The specificity (Sp) is 83.8% for LANG I and 85.3% for LANG II

- The Negative Predictive Value (NPV) is 93% for LANG I and 92.9% for LANG II

- The Positive Predictive Value (PPV) is 10.8% for LANG I and 10.8% for LANG I

Lang I and Lang II tests can be performed very early. They show in a simple way the presence of stereoscopic vision. Thus, numerous suggestions have been proposed regarding their use as an alternative or complement to the measurement of visual acuity in the application of some preschool vision screening programs. However, for several reasons, primarily the uncertainty of the reference criteria, this screening method has not been widely adopted. For this, we wanted to make our modest contribution in this direction. Our results in relation to the specificity of LANG II (85.3%) are similar to those reported by OHLSSON (96%). The Negative Predictive Value is 93% for LANG I and 92.9% for LANG II. This makes it possible to predict the absence of anisometropia when the child responds correctly to the LANG I and/or LANG II tests.

Lang tests are easy to perform, requiring no special ophthalmological training. The images shown do not require any special glass to view. The studies reported on the validity of these tests are currently sparse. The results of these tests are considered uncertain for screening for amblyopia and/or strabismus. However, these 2 tests have significant specificity that can contribute as a complement to the measurement of visual acuity rather than as a replacement product in vision screening programs in preschool settings.