...retina. In a near-sighted person the curvature of the cornea and crystalline lens is so great that the rays of light are brought to a focus in front of the retina. The object is therefore not distinctly seen. This is remedied either by holding the object nearer to...

...Of the abnormal conditions of the globe, we have, 1st, Brachymetropia—shortsightedness—in which the rays of light are brought to a focus in front of the retina, in consequence of the abnormal distance at which the latter is placed from the lens; 2d, the opposite...

...spectacles perfectly intelligible. In the case of a near-sighted person, the defect in his sight is that rays of light are brought to a focus in front of the retina, the cornea and crystalline lens making the rays converge too much. To remedy this, it is necessary...

...(Short sight}.—The anteroposterior axis of the eyeball is of too great a length, so that parallel rays of light are brought to a focus in front of the retina instead of upon it. In order to obviate this we employ concave lenses, which render the parallel rays...

...(Short sight).—The anteroposterior axis of the eyeball is of too great a length, so that parallel rays of light are brought to a focus in front of the retina instead of upon it. In order to obviate this we employ concave lenses, which render the parallel rays...

...surface in the present instance prevented, of course, any reunion of the rays into a single focus. When the rays of light are brought to a focus in front of or behind the retina, as in the ordinary anomalies of refraction, we can bring the focus to its proper...

...is due to an abnormal elongation of the eye ball, and too great a degree of convexity of the lens. The rays of light are brought to a focus in front of the retina, and the images are indistinct and blurred (Fig. 116, 4). The eye is naturally accommodated for a near point,...

...(Short sight).—The anteroposterior axis of the eyeball is of too great a length, so that parallel rays of light are brought to a focus in front of the retina instead of upon it. In order to obviate this we employ concave lenses, which render the parallel rays...

...cases of myopia the eyeball is too long from before badwards, so that when the accommodation is at rest rays of light are brought to a focus in front of the retina. The posterior part of the globe of the eye in myopia protruding so far backward that, although the...

...of myopia the eyeball is too long from before backwards, so that when the accommodation is at rest rays of light are brought to a focus in front of the retina. The posterior part of the globe of the eye in myopia protruding so far backward that, although the...