Binocular single vision is tested by ?

Ans. is 'b' i.e., Synoptophore Grades of binocular single vision There are three grades of binocular single vision, which are best tested with the help of a synoptophore. 1. Grade-I - Simultaneous perception It is the power to see two dissimilar objects stimultaneously. It is tested by projecting two dissimilar objects (which can be joined or superimposed to form a complete picture) in front of the two eyes. For example, when a picture of a bird is projected onto the right eye and that of a cage onto the left eye, an individual with presence of simultaneous perception will see the bird in the cage. 2. Grade-II - Fusion It consists of the power to superimpose two incomplete but similar images to from one complete image. The ability of the subject to continue to see one complete picture when his eyes are made to converge or diverge a few degrees, gives the positive and negative fusion range, respectively. 3. Grade-III - Stereopsis It consists of the ability to perceive the third dimension (depth perception). It can be tested with stereopsis slides in synoptophore.