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Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Chapter II. HYPEROPIA. No. 1, Showing the hyperoplc eye in which parallel rays of light do not form a focus until they have passed the retina. No. 2, with the convex lens before the eye the light forms a focus on the retina. THE defects of the eye are first divided into two classes, according to the length of the eye-ball from the cornea to the retina. First?Hyperopia, or far sight, due to a short eye-ball. Second?Myopia, or near sight, due to a long eye-ball. Hyperopia is again divided into latent (concealed) and manifest. In latent hyperopia, the defect being concealed, the vision is apparently normal, the patient being able to read the finest print and to see distant objects clearly also. In manifest hyperopia there is dimness of vision for reading, and if there is considerable hyperopia there is dimness in distant vision also. This dimness of sight in manifest hyperopia ia very annoying, but it is not such a strain on the nervous system as latent hyperopia; but in most cases whenever there is manifest hyperopia there is some latent also, as the nerves and muscles of the eye are ever striving to give the best vision possible. To do this they must overcome as much of the hyperopia as possible, and as part of it is overcome, then part of it is latent. Now let us look at the condition of the nerves and muscles of the hyperopic eye. We know that in the normal eye the nerves and muscles are at rest when looking at distant objects, but in the hyperopic eye we will learn that the nerves and muscles are under constant strain, both for distant and close vision. We will illustrate by showing how the light will focus at certain distances from a bi-convex lens. Take a + 6 D. lens and hold it in front of a piece of white paper or card board and let the light from...