Remember that it is important to check a patient's peripheral vision when concerned about stroke, and when performing a neurological exam in general.
Recognizing grossly abnormal peripheral vision often suggests the presence of various types of visual field cuts and helps localize a stroke lesion.
When performing a general, very gross examination for peripheral vision abnormalities:
It is sometimes helpful to ask the patient to cover the eye that you are NOT checking for abnormality at the time.
Ask the patient to look straight ahead.
Ask the patient to tell you when they are able to see the long, narrow object (i.e. your finger, a pencil, etc.) that you slowly move forward into their view, starting from the point where the finger tips of the patient's laterally abducted arm would be (i.e. the object begins at a distance approximately equal to the patient's arm length).
Using this axis of reference, normal peripheral vision should occur at 45 degrees or less.