. Refraction and motility of the eye, with chapters on color blindness and the field of vision . Fig. 118. reattached and continue its function, and the individualwith the aid of experience revises his judgment as to themeaning of retinal sensation from this area, and things nolonger seem distorted (Metamorphopsia). Fig. 118 shows a field often found in neurasthenia inwhich owing to fatigue of the retina when continuallytested, the field keeps getting gradually and regularlysmaller, recovering its function after a slight rest. Centralvision may also show similar evidences of fatigue, but there
. Refraction and motility of the eye, with chapters on color blindness and the field of vision . Fig. 118. reattached and continue its function, and the individualwith the aid of experience revises his judgment as to themeaning of retinal sensation from this area, and things nolonger seem distorted (Metamorphopsia). Fig. 118 shows a field often found in neurasthenia inwhich owing to fatigue of the retina when continuallytested, the field keeps getting gradually and regularlysmaller, recovering its function after a slight rest. Centralvision may also show similar evidences of fatigue, but therelations between white and the colors is a constant hysteria, on the other hand, the field is sometimes THE FIELD OF VISION. 349 absurdly small without apparently interfering with orienta-tion, and irregular and inconstant defects may be Fig. 119. The color fields are often reversed and larger than the fieldsfor white. It can readily be seen that defects in the visual fields 350 REFRACTION AND MOTILITY OF THE EYE. may not only be due to defects in one or both eyes, prevent-ing retinal stimulation, but that even when peripheral partsare normal, there may be lesions in the conductionapparatus or others further back which prevent theirreception by the brain itself. For this reason a carefulstudy of the diagram which shows the paths of theseimpulses is advisable, The retinal fibres unite to form the optic nerve whichafter penetrating the lamina cribrosa, passes through looseconnective tissue to the apex of the orbit where it emergesthrough the optic foramen. This is really a short bonycanal, which the nerve fits snugly so that at this point it isparticularly subject to compression and constriction. In the optic groove of the sphenoid the nerve uniteswith its fellow from the other side to form the the optic tra
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Keywords: ., boo, bookcentury1900, bookdecade1920, booksubjecteye, bookyear1920
