Binocularity degrees 28 7.3 ALL RIGHTS RESERVED © DIAGNOSTICS 1° degree - Simultaneous perception or Biocularity The development of Binocularity occurs gradually, and it is possible to divide it into different steps. Worth distinguished three phases and named them "degrees of development of binocular vision": 1° degree - Simultaneous perception or Biocularity: the simultaneous perception of the two eyes without the possibility of binocular fusion. Through this phase it is possible to investigate the presence or absence of suspension or suppression and to detect heterophoria. Test example: Test with prism Von Graefe. 2° degree - Flat fusion or Binocularity: two images strike the two retinas in corresponding points, after having reached the occipital visual cortex, and are associated in a single image that represents the fusion of the two primitive images. Test examples: Worth's lights or Red Filter Test. 3° degree - Stereopsis: a visual-perceptive process which, starting from two slightly different monocular retinal images, leads to the sensation of depth. It occurs only at the level of the striated cortex where the re-elaboration of the information of the two eyes occurs. Examples of stereotests; Lang, Titmus, Butterfly. Ref. 08307 Prism of 6 prismatic diopters (∆) useful to detect the first degree of biocularity. The prism must be paced with a vertical base in front of one of the eyes while the person is fixing a point-like target projected from a distance. A prism of this power cannot be compensated for by vertical fusion reserves, therefore, under normal conditions, the person should report vertical diplopia. Otherwise it could be a case of suppression. Before proceeding with further investigations, move the prism to the other eye or flip the base PRISM 6 ∆ 1 pc.
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