Screening merits of the Lang II, Frisby, Randot, Titmus, and TNO stereo tests

Purpose: Previous works show a pronounced disagreement on the reliability of stereo tests as screening tools for amblyopia and strabismus. This study's aim was to compare the ability of the Lang II, Frisby, Randot, Titmus, and TNO stereo tests to detect amblyopia and strabismus with visual acuity testing and cover testing. Methods. A total of 1035 school children aged 12 to 13 years were examined in a field study in Monterrey, Mexico. In addition to the 5 stereo tests, the examination included visual acuity, cover testing, refraction (skiascopy), and inspection of the red reflex and posterior pole. Results. Sensitivity ranged from 17% to 47% (Frisby-Titmus-Lang II-Randot-TNO, in order of occurrence). Of the 60 subjects with strabismus and/or amblyopia, only 8 subjects were identified by all 5 stereo tests. A considerable number of subjects (25), the majority of whom were amblyopic (23 subjects), were not identified by any of the tests. All stereo tests showed higher sensitivities for strabismus than for amblyopia. Conclusion: None of the 5 stereo tests studied is suitable for screening for amblyopia or strabismus. The results of both ocularly normal subjects and subjects with strabismus and/or amblyopia are variable, and there is no way of separating normal response from abnormal response.