What is a visual acuity test? Show
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:
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. SnellenThe 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 EIn 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
Cranial Nerve I – Olfactory NerveThe 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.
Cranial Nerve II – Optic NerveNext, 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
Testing Distant Vision
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 fieldsConfrontation
Test the ocular fundi.
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
Testing accommodation and convergence of pupil response.
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
The Wagon Wheel method
Cranial Nerve V – Trigeminal NerveThe 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.
Next test the corneal reflex.
Next, test the motor function of the nerve.You are assessing for any pain, muscle spasms or deviation of the mandible.
Cranial Nerve VII – Facial NerveThe 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.
Second, test the muscle strength of the upper and lower facial muscles.
Third, test the sense of taste.
Cranial Nerve VIII – Vestibulocochlear NerveThe 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.
Performing the Weber test.
Performing the Romberg test.
Cranial Nerve IX – Glossopharyngeal and Cranial Nerve X – Vagus NerveThe 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.
Next, test the gag reflex.This test assesses the sensory aspect of cranial nerve IX and the motor activity of cranial nerve X.
Finally, test the motor activity of the pharynx.
Cranial Nerve XI – Accessory Nerve or Spinal Accessory NerveThe 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.
Second, test the sternocleidomastoid muscle.
Cranial Nerve XII – Hypoglossal NerveThe hypoglossal nerve supplies the muscles of the tongue. This assessment involves testing the movement of the tongue.
Next, test the strength of the tongue.
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. ReferenceBickley 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. |