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Cranial nerve II - the Optic nerve


Signs and Symptoms of Lesions

Blind spots; tunnel vision and/or day blindness, night blindness, color blindness.


Optic Nerve Test:

There are three steps in testing cranial nerve II.

1.  Visual Acuity – For normal vision, use Snellen’s card test.  For subnormal vision, count and move fingers. For markedly subnormal cases, use light perception and light projection.  Standard reading cards are used for near vision. 

Optic nerve test 1

2.   Red Eye Reflex – Through the use of a penlight or ophthalmoscope, the practitioner briefly shines a light into one of the individual’s eyes, observing for pupil constriction.  Should constriction not occur, consider ophthalmic disorders or possible multiple sclerosis.  Perform bilaterally.

Optic nerve test 2

3.   Visual field-test – With the practitioner sitting approximately 3 feet in front of the individual, the individual is requested to close one eye.  While the individual is staring at the practitioner’s nose, the practitioner holds one hand beneath and out of view of the individual.  While flipping the index finger, or using a pen, the practitioner gradually elevates their hand until the person states they see it.  Continuing to elevate the hand, the individual should remark exactly when they lose sight of the finger outside their visual field. This technique should be performed through vertical, horizontal and oblique planes while comparing one eye’s visual field against the other.


Optic nerve test 3

Do not be surprised in the performance of this test if individuals have blind spots (scotomas) or in other words, they view the finger from the periphery and during motion they lose sight of the finger only to regain sight of it before losing it again at the other periphery.  Central vision loss is common with conditions like Macular Degeneration and Retinitis Pigmentosa.  Loss of peripheral vision is common in Tunnel Vision or Tubular Vision.

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