The Refraction and Accommodation of the Eye and Their Anomalies

Front Cover
Pentland, 1886 - 600 pages

From inside the book

Other editions - View all

Common terms and phrases

Popular passages

Page 455 - It ought to bo as broad as the thighs are long (the distance from the popliteal space to the back). 3. The front rounded edge of the bench ought to project two or three centimeters beyond the inner edge of the table. 4. The seat should be sufficiently high so that the child can, when writing, conveniently rest the forearms on the table, without raising the shoulders and without bending the neck or leaning forward. 5. The lower part of the child's back should be properly supported when the scholar...
Page xv - This amounts to the same with saying, that, in the case before us, the sine of the angle of incidence is to the sine of the angle of refraction in a given ratio.
Page 561 - The term presbyopia is, therefore, to be restricted to the condition, in which, as the result of the increase of years, the range of accommodation is diminished, and the vision of near objects is interfered with.
Page 35 - AA' and BB' at the points A' and B', which determine the position and magnitude of the image. Since the point A' lies above the prin cipal axis when the image is on the same side of the lens as the object, and...
Page 455 - In order that this requirement may be met it is necessary (l)That the bench be raised above the floor the length of the child's legs (measured from the popliteal space to the sole of the foot). (2) It ought to be as broad as the thighs are long (the distance from the popliteal space to the back). (3) The front rounded edge of the bench ought to project two or three centimeters beyond the inner edge of the table. (4) The seat should be sufficiently high so that the child can, when writing, conveniently...
Page 136 - Distance from the anterior surface of the cornea to the anterior surface of the lens, 3.6 millimeters ; distance from the posterior surface of the lens tc the retina, 15.
Page 455 - ... sufficiently high so that the child can, when writing, conveniently rest the forearms on the table, without raising the shoulders and without bending the neck or leaning forward. 5. The lower part of the child's back should be properly supported when the scholar is reading by means of a short chair back. These conditions vary with the growth of the child, and the above measurements should be repeated and the scholars assigned suitable seats at least as often as once in six months.
Page 478 - Laudolt has laid it down as a general rule, in all degrees of myopia, " that a myope must be prohibited from wearing a concave glass for any distance at which he can see clearly without accommodation.
Page 507 - Anisometropia exists whenever the two eyes demand, in order that each shall possess its maximum of visual acuteness, or in order to present to the observer the same clearness in their ophthalmoscopic images, two different numbers of spectacle glasses.
Page 21 - In other words, the directions of any incident ray, and of the corresponding emergent ray, pierce the first and second principal planes in two points situated on the same side of, and at the same distance from, the principal axis of the system. The second principal plane is the optical image of the first, and vice versa.

Bibliographic information