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She held in her hand his last bill unpaid; and though she had paid a score of his bills, yet her eyesight now was nearly gone. Her doctor called it "retinal failure"; and it had steadily advanced, whatever it was. Now she knew that there was no hope. She greeted the homecoming of her room-mate each nightfall with eagerness.
A network of associations is thus formed, whereby the sensation of each retinal point is connected with all the others in a manner which is that of points in a plane. Every visible point becomes thus a point in a field, and has a felt radiation of lines of possible motion about it.
The retina alone comprises three layers of nervous elements multipolar cells, bipolar cells, visual cells each of which has its individuality and is undoubtedly a very complicated organism: so complicated, indeed, is the retinal membrane in its intimate structure, that no simple description can give an adequate idea of it.
The fact is that we have to take into consideration two other factors in the process, which we call "seeing," besides the duration of the retinal impression or excitation. These are, first, attention, and second, judgment. We are apt to think that "seeing" is a simple, straightforward sort of thing, whereas it is really a strangely complex and delusive process.
For example, an illusory sense of direction arises by the simple action of closing one eye, say the left, and pressing the other eyeball with one of the fingers a little outwards, that is to the right. The result of this movement is, of course, to transfer the retinal picture to new nervous elements further to the right.
Bowman, one of our most excellent oculists, was then consulted. Mr. Bowman wrote to me as follows: "Such symptoms as exist point rather to disturbed retinal function than to any brain-mischief. It is, however, quite likely that what you fear for the brain may have had its counterpart in the nerve-structures of the eye, and as he is short-sighted, this tendency may be further intensified." Mr.
Other forms of retinal injury from too great or too prolonged exposure to light are "moon-blindness," due to sleeping with the eyes exposed to bright moonlight, and that due to lightning a case, e.g., being reported by Knies. Silex also reports such a case and reviews the reported cases, 25 in number, in ten of which cataract ensued.
What looks like the movement of something across the field of vision is made known to us either by the feeling of the ocular muscles, if the eye follows the object, or through the sequence of locally distinct retinal impressions, if the eye is stationary.
I assure you that within the next hour you'll know more about Project Brainchild than I've been able to find out in two years.... Now put your face in here and keep your eyes open. When you can see the target spot, focus on it and tell me." Mike the Angel put his face in the rest for the retinal photos. The soft foam rubber adjusted around his face, and he was looking into blackness.
The orbit is pierced through its posterior surface by an opening through which the nerve of sight, the optic, passes to the eyeball. We may think of the optic nerve holding the eyeball much as the stem holds the apple. It is the function of this most important nerve to transmit retinal impressions to the seat of consciousness in the brain, where they are interpreted.
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