AN EYESIGHT ANOMALY.

Gisborne Times, Volume XLVIII, Issue 4475, 16 February 1917, Page 3

AN EYESIGHT ANOMALY.

Strange as it may seem, few of the two-eyed animals have true binocular vision. Most of them have their eyes situated on the two opposite directions; and, while it is true that, by reason of the sweep of their vision they eaii seen not only to right- and left’, but more or less to the front and rear, it is also true that, in order to get a keener view of what is before, an animal will often turn its head, directing one eye toward the object of contemplation. It must be that it centres its attention upon what the directed eye is seeing, and ignores what the other eye beholds. And doubtless the same thin a: is done even when the head is held naturally. Here are seen objects to left and right: the attention may be directed to either the one or the other. Now (says a writer in the Scientific© American) all this is monocular vision, in spite of the fact that two eyes are open and seeing; it is only one eye that is engaging the attention. A very few of the-lower animals, like some of the monkeys, seem to possess the true binocular vision—that is, they centre both eyes on the same object at the same time, and blend the two images into one. The dog is not one of these, in spite of the forward position of its eyes ; it is but a- single'eye that the dog centres upon the object of interest. Man, on the other hand, possessing a well-develop-ed faculty of using both eyes upon the same object with successful results, probably leads the entire procession i'n the matter of binocular vision. Some believe that, in the evolution of life, binocular vision is a recently acquired faculty on the part oi man, and they point to its imperfections as indicative of its recent origin ; it has not yet had time to attain its full development. For there exist more imperfections in binocular seeing than most people suppose. Oculists are finding that a considerable percentage of mankind do not habitually use binocular vision. While they have two eyes, they see consciously with but one. Only one eye at- a- time is concentrated upon the object to he observed; the other looks as it may. Like the off eye of the lower animal, its impressions are ignored bv the mind. This is true not only of people whose eyes are divergent or willed; in many cases where the eyes are normally forward, one of the two organs shirks duty, either constantly or bv alternation with the other.