Q&A When

Which of these measures of visual acuity would the nurse assess when testing the optic nerve?

What is a visual acuity test?

A visual acuity test is an eye exam that checks how well you see the details of a letter or symbol from a specific distance.

Visual acuity refers to your ability to discern the shapes and details of the things you see. It’s just one factor in your overall vision. Others include color vision, peripheral vision, and depth perception.

There are several different types of visual acuity tests, most of which are very simple. Depending on the type of test and where it’s conducted, the exam can be performed by:

an optometrist
an ophthalmologist
an optician
a technician
a nurse

No risks are associated with visual acuity tests, and you don’t need any special preparation.

You may need an eye exam if you feel you’re experiencing a vision problem or your vision has changed. A visual acuity test is one part of a comprehensive eye exam.

Children frequently take visual acuity tests. Early testing and detection of vision problems can prevent issues from getting worse.

Optometrists, driver’s license bureaus, and many other organizations use this test to check your ability to see.

Two commonly used tests are Snellen and random E.

Snellen

The Snellen test uses a chart of letters or symbols. You’ve probably seen the chart in a school nurse’s office or eye doctor’s office. The letters are different sizes and arranged in rows and columns. Viewed from 14 to 20 feet away, this chart helps determine how well you can see letters and shapes.

During the test, you’ll sit or stand a specific distance away from the chart and cover one eye. You’ll read out loud the letters you see with your uncovered eye. You’ll repeat this process with your other eye. Typically, your doctor will ask you to read smaller and smaller letters until you can no longer accurately distinguish letters.

Random E

In the random E test, you’ll identify the direction the letter “E” is facing. Looking at the letter on a chart or projection, you’ll point in the direction the letter is facing: up, down, left, or right.

These tests tend to be more sophisticated when performed at an eye clinic than in a nurse’s office. At an eye doctor’s office, the chart might be projected or shown as a mirror reflection. You’ll look at the chart through a variety of different lenses. Your doctor will switch out the lenses until you can see the chart clearly. This helps determine your ideal eyeglass or contact lens prescription, if you need vision correction.

Visual acuity is expressed as a fraction, such as 20/20. Having 20/20 vision means that your visual acuity at 20 feet away from an object is normal. If you have 20/40 vision, for example, that means you need to be 20 feet away to see an object that people can normally see from 40 feet away.

If your visual acuity is not 20/20, you may need corrective eyeglasses, contact lenses, or surgery. You might also have an eye condition, such as an eye infection or injury, that needs to be treated. You and your doctor will discuss your test results as well as any treatment or correction that might be necessary.

The nervous system is a very complex system which is vital to the functioning of the human body. The nervous system is comprised of the central nervous system (CNS) and peripheral nervous system (PNS). There are 31 pairs of spinal nerves and 12 pairs of cranial nerves. Below are the procedures for performing an assessment of the cranial nerves.

For more information about performing a nursing health assessment read the article Tips for A Better Nursing Health Assessment. This will help you proceed through an assessment including the nervous system as you move from head-to-toe.

During a complete health assessment of the nervous system, you will perform an assessment of the cranial nerves, motor function, sensory function, and reflexes. Below is a complete assessment of the cranial nerves. Read our article 5 Tips for Performing a Nursing Health Assessment of the Nervous System for assessment of the motor function, sensory function, and reflexes.

Cranial Nerves

DesignationNumberNerveTypeFunction

I	1	Olfactory nerve	Sensory	The nerve of smell
II	2	Optic nerve	Sensory	The nerve of vision
III	3	Oculomotor Nerve	Motor	Muscles of eye movement
IV	4	Trochlear Nerve	Motor	Muscles of eye movement
V	5	Trigeminal Nerve	Mixed	For the face and muscle for chewing
VI	6	Abducens Nerve	Motor	Muscles of eye movement
VII	7	Facial Nerve	Motor	Facial expression
VIII	8	Vestibulocochlear Nerve	Sensory	Hearing and balance
IX	9	Glossopharyngeal Nerve	Mixed	Throat and taste (tongue and pharynx)
X	10	Vagus Nerve	Mixed	The nerves of the thorax and abdominal region (heart, lungs, viscera etc)
XI	11	Accessory Nerve	Mixed, mostly motor	The nerve of the throat and neck muscles
XII	12	Hypoglossal Nerve	Mixed, mostly motor	The tongue muscles.

Cranial Nerve I – Olfactory Nerve

The olfactory nerve is the sensory nerve of smell. Before beginning, have some type of aromatic substance available such as coffee, toothpaste, peppermint or soap to use as part of the assessment.

Begin by testing the patency of each nostril.
The patient should be able to identify the odor on each side of the nose.
Avoid noxious stimulants such as ammonia and alcohol wipes.

Cranial Nerve II – Optic Nerve

Next, test the optic nerve. The optic nerve is responsible for visual processes. Assessment of the optic nerve involves the testing of visual acuity, visual fields, and the ocular fundi.

Testing visual acuity involves testing near and distant vision. Visual fields are tested by confrontation. Confrontation measures peripheral vision. Test of the ocular fundi requires the use of an ophthalmoscope.

Testing Near Vision

You may test a patient’s near vision by asking the patient to read from a magazine or a newspaper.
Observe how far or close the patient holds the object away from the face.
Also, note the position of the patient’s head.

Testing Distant Vision

Use a Snelling chart. Proceed in the following manner.
Have the patient cover one eye with a card or an eye cover.
Have the patient read from the left to the right down the chart starting at the top line.
Instruct the patient to read to the smallest line of letters they can see.
Have the patient cover the other eye and repeat the steps above.
Next, ask the patient to read from top to bottom of the chart to the smallest line that they can see with both eyes uncovered.
If the patient wears corrective lenses or contacts for distant vision, test them first with eyeglasses or their contact lenses. Then, test them without their glasses or contact lenses.
The results of the tests are recorded as a fraction. The numerator indicates the distance from the chart which is normally 20 ft. The denominator indicates the distance at which the person with normal vision can read the last line. The lines on the chart are numbered.

Normal vision is 20/20. This means the patient is 20 feet away from the chart and can read the line numbered 20.

If the patient’s vision is 20/30 then the patient reads at 20 ft what a person with normal vision reads at 30 ft.

Observe the patient while they are reading the chart. If a patient is unable to read more than one-half of the letters on a line record the number of the line above.

Testing visual fields

Confrontation

Have the patient sit or stand about 2-3 ft away from you at eye level.
Tell the patient you will be testing their peripheral vision.
Have the patient cover one eye with a card.
Cover your eye on the same side as the patients.
Have the patient look into your uncovered eye.
Hold a penlight in your hand above your heads and move the object into the field of vision.
Do this from at least four different directions, downward toward the nose and upward toward the nose, etc.
Have the patient say “now” when they first see the object.
Repeat this procedure on the other eye.
If the patient cannot see the object at the same time as you, there may be some peripheral vision loss. This test assumes the nurse has normal peripheral vision. And remember the patient has a possible neurological dysfunction.

Test the ocular fundi.

An ophthalmoscope is used to examine the fundus of the eye. This is mostly an advanced skill performed by physicians and nurse practitioners but it is good to know what is occurring doing an ophthalmic examination.
During this procedure, you will normally locate the optic disc.
Describe the color and shape of the optic disc.

Cranial Nerve III – Oculomotor, Cranial Nerve IV – Trochlear, and Cranial Nerve VI – Abducens.

The oculomotor nerve, trochlear nerve, and abducens nerve (cranial nerves III, IV, and VI) all work together, therefore, are assessed together.

During this test, you will assess direct and consensual pupillary reaction to light, convergence, accommodation of the eyes and the six cardinal points of gaze.

Testing Consensual Pupillary Reaction to Light

To perform the direct and consensual pupillary reaction test, dim the lights in the room.
Explain to the patient that you will be shining a light directly at each eye.
Explain to the patient that they must stare straight ahead during this procedure.
Moving in from the patient’s side, shine the light directly into one eye.
Observe for constriction of the illuminated eye.
This is a direct pupillary reaction to light.
Also, observe the simultaneous reaction of the other pupil. or constriction of the pupil not illuminated.
This is consensual constriction.
The illuminated eye should be a little faster and greater than the consensual reaction.
Also, during this procedure inspect the patient’s pupil.
The pupil should be round, equal in size and shape and in the center of the eye.

Testing accommodation and convergence of pupil response.

For accommodation and convergence, you will be testing the muscles of the eye.
Ask the patient to stare straight ahead at a distant point.
Hold a penlight about 4 to 5in from the patient’s nose, then ask the client to shift the gaze from the distant point to the penlight.
The eyes should turn inward. This is convergence.
The pupils also should constrict as the eyes focus on the penlight.
The pupillary change is accommodation, a change in the size to adjust vision from far to near.

A normal response to pupillary testing is recorded as PERRLA, (pupils equal, round, react to light, and accommodation).

Testing the six cardinal fields of gaze.

There are two methods used for this assessment. The first is the “H” Method. The second is the “Wagon Wheel” Method. These procedures test eye movement and the muscles of the eye.

During the procedure, you will be assessing the patient’s ability to follow your movement with their eyes. Assess the patient eyes while performing the procedure. You are looking for the presence of any abnormalities such as nystagmus in one or both eyes. Nystagmus is the rapid back and forth jerky movement of the eyeball with the rapid lateral movement of the eyeball.

The “H” Method

For this procedure, you will need a penlight used as an object for the patient to focus on.
Stand about two feet in front of the patient.
Explain to the patient that they must keep their head still and follow the penlight as you move it in several directions in front of their eyes.
You will be drawing an “H” in front of the patient.
First, start with the penlight midline.
Have the patient focus on the penlight.
Now, move the penlight to the left, then straight up and then straight down. (This movement will form the left half of the “H”)
Now drop the penlight from that position and reposition it at the midline again.
Have the patient refocus on the penlight.
Now move the penlight to the right then straight up and then straight down. (This movement should form the right side of the “H”)

The Wagon Wheel method

For this procedure, you will need a penlight used as an object for the patient to focus on.
Stand about two feet in front of the patient.
Explain to the patient that they must keep their head still and follow the penlight as you move it in several directions in front of their eyes.
You will be drawing a wagon wheel or a star shape.
Have the patient focus on the penlight.
Now, start at midline and move the penlight in the direction to form a star or a wagon wheel.
Example. Move penlight from the middle to–>right upper to–>middle to–> right lower to–> middle to–>left upper to–>middle to–> right lower until you have made at least six straight lines.
Always return the penlight to the center position before changing directions.

Cranial Nerve V – Trigeminal Nerve

The trigeminal nerve is the main nerve of the face. You will be testing the sensory function of the nerve. You will be looking for a loss of sensation, pain or any fine rapid muscle movements called fasciculations.

Test the sensory function of the nerve.

Ask the patient to close both eyes.
Touch the patient face with a wisp of cotton.
Have the patient to say “now” every time they feel the cotton.
Repeat this on the patient’s chin and forehead to assess all three branches of the nerve.

Next test the corneal reflex.

A patient’s contact lenses will need to be removed.
Have the patient look straight ahead.
Use a wisp of cotton to touch the patient’s cornea from the side.
The patient should blink.

Next, test the motor function of the nerve.

You are assessing for any pain, muscle spasms or deviation of the mandible.

Let the patient know you will be touching their face.
Palpate the patient’s masseter and temporalis muscles and ask the patient to clench their teeth tightly.
Note the strength of the muscle.
Next, ask the patient to open and close the mouth several times.
You are looking for symmetry of movement of the mandible and any deviation from the midline.

Cranial Nerve VII – Facial Nerve

The facial nerve is a motor nerve. This nerve supplies the motor fibers used for facial expressions and, also the salivary and lacrimal glands.

First, you will be assessing the symmetry of facial movement.

To test this nerve you will be asking the patient to make several facial expressions.
Have the patient perform the following facial expressions.
1. Smile showing their teeth
2. close both eyes
3. puff their cheeks
4. frown
5. and raising their eyebrows.

Second, test the muscle strength of the upper and lower facial muscles.

Have the patient close both eyes tightly and keep them closed.
Attempt to open the eyes by retracting the upper and lower eyelids simultaneously.
Then, ask the patient to puff their cheeks.
Apply pressure to the cheeks attempting to force the air out through the lips.

Third, test the sense of taste.

Gather 3 cotton-tipped applicators.
Moisten them and dab one in a sample of sugar, the second in salt and the third in lemon juice.
Touch the patient’s tongue with an applicator one at a time and ask the patient to identify the taste.
Use water to rinse the mouth between tests.

Cranial Nerve VIII – Vestibulocochlear Nerve

The vestibulocochlear nerve is a sensory nerve and is responsible for transmitting information about balance and hearing from the inner ear to the brain.

Assess the vestibulocochlear nerve using the Rinne test, the Weber test, and the Romberg test.

The Rinne test compares bone conduction with air conduction. It tests for tinnitus and deafness.

The Weber test provides lateralization of the sound. Lateralization is roughly defined as localized to one side in the presence of another side. Also, it is used to check for hearing and if a person hears better in one ear than another.

And the Romberg test assesses coordination and equilibrium. A tuning fork and your watch are used for the Weber and Rinne test.

Performing the Rinne test.

While holding the tuning fork by the handle, gently strike the fork on the palm of your hand. This will start the tuning fork vibrating.
Place the base of the tuning fork on the patient’s mastoid process.
Next, ask the patient to tell you when they no longer hear the sound.
Note the number of seconds.
Then, immediately, while the tuning fork is still vibrating, move the fork in front of the external auditory meatus. It should be 1 to 2 centimeters from the meatus.
Ask the patient to tell you again when they no longer hear the sound.
Note the number of seconds again.
Compare the time note of air conduction and bone conduction.
Normally the sound is heard twice as long by air conduction than by bone conduction.
So Air conduction should be 2 X longer than bone conduction. (Ex. Air conduction 30 seconds, bone conduction 15 seconds)

Performing the Weber test.

While holding the tuning fork by the handle, gently strike the fork on the palm of your hand. This will start the tuning fork vibrating.
Place the base of the vibrating fork against the patient’s skull. Use the midline of the anterior portion of the frontal bone or the forehead.
Ask the client if the sound is heard equally on both sides or better in one ear than the other.
A normal finding is that the patient hears equally in both ears.
Chart this as “no lateralization.”
If a patient hears the sound in one ear better than the other, the sound is lateralized. Ask the patient which ear and document.

Performing the Romberg test.

For this test stand near the patient and be prepared to support them if they lose their balance.
Ask the patient to stand with feet together and arms at side.
First, begin with eyes open, then have them close their eyes.
Wait for about 20 seconds.
The patient should be able to maintain this position with only a little swaying.
Document this as a negative Romberg. This means it is normal.

Cranial Nerve IX – Glossopharyngeal and Cranial Nerve X – Vagus Nerve

The glossopharyngeal nerve is a mixed nerve. The motor fibers carry motor information from the throat to the brain. And the sensory fibers carry impulses from the pharynx and tongue (taste buds).

The vagus nerve is the largest of the cranial nerves. This nerve provides sensation from the throat, as well as organs of the chest and abdomen, taste from the tongue and back of the throat, and muscle function of the palate.

Testing the motor activity of these nerves.

Explain to the patient that you are going to place a tongue blade in the mouth.
Have the patient open their mouth.
Use a tongue blade to depress the patient’s tongue.
Ask the patient to say “ah.”
Observe the movement of the soft palate and uvula.
The soft palate should rise. The uvula should remain midline.

Next, test the gag reflex.

This test assesses the sensory aspect of cranial nerve IX and the motor activity of cranial nerve X.

Explain to the patient that you are going to place a tongue blade in the mouth and lightly touch the throat.
Touch the posterior wall of the pharynx with a tongue depressor.
Observe the pharyngeal movement.

Finally, test the motor activity of the pharynx.

Ask the patient to drink a small amount of water.
Note the ease or difficulty of swallowing.
Also, note the quality of the voice. Is there any hoarseness while speaking?

Cranial Nerve XI – Accessory Nerve or Spinal Accessory Nerve

The accessory nerve is a mixed nerve but mostly the motor nerve of the sternocleidomastoid and trapezius muscles. During this assessment, you will check the strength and movement of the patient’s sternocleidomastoid and trapezius muscle.

First, test the trapezius muscle.

Ask the patient to shrug the shoulders.
Observe the quality of the shoulder movement, symmetry of action, and lack of fasciculations.
Test the strength of the trapezius muscle by having the patient shrug the shoulders while you resist with your hand.

Second, test the sternocleidomastoid muscle.

Ask the patient to turn their head to the right and then to the left.
Ask the patient to try to touch the right ear to the right shoulder without raising the shoulder.
Repeat on the left side.
Observe the range of motion.
Test the strength of the sternocleidomastoid muscle by asking the patient to turn their head to the left against your resisting hand.
Repeat the preceding step with the client turning to the right side.

Cranial Nerve XII – Hypoglossal Nerve

The hypoglossal nerve supplies the muscles of the tongue. This assessment involves testing the movement of the tongue.

Ask the patient to protrude the tongue.
Now, ask the patient to retract the tongue.
Ask the patient to protrude the tongue and move it to the right side and then to the left side.
You are noting the ease and equality of movement.

Next, test the strength of the tongue.

Ask the patient to push against the inside of the cheek with a tip of their tongue.
Provide resistance by pressing one or two fingers against the patient’s outer cheek.
Repeat on the other side.

In conclusion, the tips above will help you with a nursing health assessment of the cranial nerves. Perform a comprehensive or complete neurological assessment when a neurological concern or dysfunction is suspected.

A basic check or recheck of the neurological system is done during a normal head-to-toe assessment. Don’t forget to read 5 Tips for Performing a Nursing Health Assessment on the Nervous System for the additional portions of the comprehensive assessment.

Reference

Bickley LS., Szilagyi PG., (2017). Bates Guide to Physical Examination and History Taking. 12th ed. Philadelphia, PA. Wolters Kluwer/Lippincott Williams & Wilkins.Jarvis C., (2017). Physical Examination & Health Assessment. St Louis, MO. Elsevier Inc.

Mosby’s Medical Dictionary (2017). 10th ed. St Louis, MO. Elsevier Inc.

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