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2.视神经 (CN II) （1）Examine both retinas carefully with an ophthalmoscope； （2）Visual Acuity. Test visual acuity for each eye separately (by covering one eye at a time) using an eye chart. （3）Color Vision. Test each eye separately for ability to distinguish colors. Test for red desaturation, a sign of subtle asymmetry in optic nerve function seen, for example, in optic neuritis by asking the patient to cover each eye alternately while looking at a red object and report any relative dullness of the color in one eye. （4）Visual Fields. Test visual fields for each eye by asking the patient to fixate straight ahead and to report when a finger can be seen moving in each quadrant. Alternatively, ask the patient to report how many fingers are being shown in each quadrant. More precise mapping of visual fields can be done in the laboratory for patients who will be followed over time （5）Visual Extinction. Test for visual extinction on double simultaneous stimulationby asking the patients how many fingers they see when fingers are presented to both sides at the same time. In visual extinction, a form of hemineglect , patients do not report seeing the fingers on the affected (usually left) side of the visual field, although they can see fingers when they are presented to that side alone. |
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