(1) Ultrasmall angles of strabismus may escape diagnosis by conventional methods of examination and are easily overlooked. Whenever stereoacuity is reduced in the presence of apparent ocular alignment with scotoma response on the 4 diopter base-out prism test, 58 p.309 the examiner must search for microtropia or other subtle anomalies of binocular vision. For the measurement of stereoacuity we prefer random dot stereo tests, such as the TNO, Randot, or Lang test. The Titmus stereotest may be used but has the disadvantage of providing monocular clues.
(2) The amblyopia in microtropia is, as a rule, mild and rarely deeper than 20/100.
(3) The Bagolini striated lens test 58, p.251 shows anomalous retinal correspondence.
(4) Fundus examination with a Visuscope 58, p.221 or a regular direct ophthalmoscope with a built-in fixation target shows parafoveal fixation.
(5) Absence of a shift on the cover test in the presence of eccentric fixation and anomalous correspondence is interpreted as an identity between the degree of eccentricity of fixation and the angle of anomaly. 28; 58, p.309
(6) Because fixation is foveolar and there is a minute shift on the cover test, no identity exists between the fixation behavior and the state of retinal correspondence.
(7) Microtropia may occur as a primary anomaly of binocular vision 37 but is more common as a secondary microtropia.
(8) Secondary microtropia occurs as an end stage of treatment of essential infantile esotropia 37, 61 (see 1.17, 1.18, and 1.19) but may also be associated with anisometropic amblyopia or amblyopia with a history of anisometropia. 28
(9) Reduced visual acuity of one eye when measured under binocular conditions with a polaroid test indicates foveal suppression of that eye.
(10) Subnormal binocular vision occurs in a primary form in family members of patients with essential infantile esotropia. 24, p.410
(11) More frequent than the primary is the secondary form of subnormal binocular vision, which is seen as an ideal end stage of the treatment of essential infantile esotropia.