Article
Lang-I-Test: random-dot stereopsis with Anisometropia up to 3 dpt
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Authors
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M. Gräf
- Zentrum für Augenheilkunde, Justus-Liebig-Universität Gießen, Gießen
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R. Becker
- Zentrum für Augenheilkunde, Justus-Liebig-Universität Gießen, Gießen
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D. Rost
- Zentrum für Augenheilkunde, Justus-Liebig-Universität Gießen, Gießen
| Published: | September 22, 2004 |
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Outline
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Objective
The Lang-stereotest is a useful tool in pediatric screening for strabismus and amblyopia. The test is also being used in ophthalmologic-orthoptic diagnostic. Patients with manifest strabismus usually cannot recognize the random-dot-stereographs of the test. However, any isometropic ametropia will hardly be detected by the test. We wanted to investigate the threshold anisometropia where the stereographs of the Lang-I-stereotest become invisible.
Methods
An artificial anisometropia was generated by unilateral application of spherical lenses. Fifteen volunteers aged 18-53 years were examined. The refraction was corrected. All the persons had normal visual acuity and were aquainted with the Lang-stereotest. Ten persons got concave lenses of increasing power in steps of 0.5 dpt in front of one eye. In 5 persons and in 5 additional volunteers, the same procedure was repeated using convex lenses. The persons had to describe the perceptibility of the 3 stereographs at a distance of 0.4 m. Three answers were possible, (1) recognition of the stereographs, (2) perception of any contour at the site of the stereographs, and (3) no apparent contour at all.
Results
The stereographs were recognized up to a hypermetropization of one eye of 2.5 dpt. Starting at 3.0 dpt, the recognition of the 3 stereographs was severely disturbed. At an anisometropia of about 3.5 dpt, even the contours visible at the site of the stereographs disappeared. Using convex lenses, there were corresponding thresholds of recognition and detection of the stereographs. The inter-individual scatter of these thresholds was low.
Conclusions
The Lang-I-stereotest cannot reliably detect an anisometropia. The stereographs become invisible at an anisometropia of about 3 dpt. Thus, global stereopsis proved by the Lang-stereotest does not exclude an amblyogenic anisometropia and a possible refractive amblyopia.
