The Cure of Imperfect Sight by Treatment
Without Glasses - online book

The Original Bates Method, for correcting vision defects

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CHAPTER XI CENTRAL FIXATION
T HE eye is a miniature camera, corresponding in many ways very exactly to the inanimate ma chine used in photography. In one respect, however, there is a great difference between the two instruments. The sensitive plate of the camera is equally sensitive in every part; but the retina has a point of maximum sensitiveness, and every other part is less sen sitive in proportion as it is removed from that point. This point of maximum sensitiveness is called the "fovea centralis," literally the "central pit."
The retina, although it is an extremely delicate mem brane, varying in thickness from one-eightieth of an inch to less than half that amount, is highly complex. It is composed of nine layers, only one of which is supposed to be capable of receiving visual impressions. This layer is composed of minute rodlike and conical bodies which vary in form and are distributed very differently in its different parts. In the center of the retina is a small circular elevation known, from the yellow color which it assumes in death and sometimes also in life, as the "mac ula lutea," literally the "yellow spot." In the center of this spot is the fovea, a deep depression of darker color. In the center of this depression there are no rods, and the cones are elongated and pressed very closely together. The other layers, on the contrary, become here extremely thin, or disappear altogether, so that the cones are cov ered with barely perceptible traces of them. Beyond the center of the fovea the cones become thicker and fewer
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