Download Title: Vision and hearing testing

Title: Vision and hearing testing
Teacher: Magdalena Gibas MD PhD,
Coll. Anatomicum, 6 Święcicki Street, Dept. of Physiology
I. Vision – examination of the visual system
A. Examination of the visual acuity
The most rewarding single test of ocular function is the evaluation of visual acuity. Reduced
acuity will betray the presence of great variety of diseases as well as the need for refractive
correction. Determination of visual acuity should be a part of every complete physical
examination.
1. Distant acuity is measured with Snellen’s chart.
a. The chart is read while standing at a distance of 20 feet=6m (5m in Poland).
b. Visual acuity is expressed in a fraction — such as 20/20 vision (or 1.0;20/20=1.0).
c. The top number refers to your distance from the eye chart,
d. The bottom number indicates the distance at which a person with normal eyesight could
correctly read the line patient reads.
e. 20/20 (1.0) vision means that patient can see objects clearly from 20 feet away that a person
with normal vision could see clearly from 20 feet away.
f. However, if patient’s visual acuity is 20/50 (0.4), the line patient reads correctly at 20 feet
could be read by a person with normal vision at 50 feet.
2. Measurement of near vision is relatively unimportant as a routine procedure except in
patients complaining specifically of reading difficulty or in persons over 40 years of age. With
increasing age the lens of the eye becomes less flexible, resulting in loss of accommodation
for near vision, which interferes with reading. This condition is referred to as presbyopia.
B. Examination of the color vision with Ishihara charts
1. The Ishihara charts are the plates on which are printed figures or numbers. The figures and
numbers are made up of colors that are liable to look the same as the background to an
individual who is color-blind. The plates are held 75 cm. from the subject and tilted so that
the plane of the paper is at right angles to the line of vision. The numerals which are seen on
plates are stated, and each answer should be given without more than three seconds delay.
To explain the results of testing a specially designed table is used.
C. Examination of the visual field
The visual field of the eye is the portion of the external world visible out of the eye. The
visual fields are mapped with an instrument called a perimeter. The process is refereed to as
perimetry. Usually automated perimetry is performed (with computer).
D. Ophtalmoscopic examination
Physical examination should include careful study of the details of the posterior eye /fundus/
with an ophthalmoscope. It examines the back of the eye, including retina, optic disc,
choroids and blood vessels. Doctor usually uses special eyedrops to dilate patient’s pupils,
opening them wider. In addition to the detection of ocular disease this procedure will permit
the diagnosis of serious systemic disorders.
E. Keratoscopy – examination of cornea shape.
F. Slit-lamp examination.
1.A slit lamp allows the doctor to see the structures at the front of patient’s eye using a
microscope — called a slit lamp
2.Doctor uses this light to examine: cornea, iris, lens, and anterior chamber of the eye.
II. Hearing
A. Otoscopy – to observe tympanic membrane. Loss of hearing may be caused by otitis media
(inflammation of middle ear), which requires otoscopy for complete diagnosis and appropriate
treatment.
B. Tunning fork tests - To distinguish between nerve and conduction deafness.
WEBER
RINNE
SCHWABACH
METHOD
Base of vibrating tuning Base of vibrating
Bone conduction of
fork placed on vertex of tuning fork placed on patient compared with
skull
mastoid process untill that of normal subject
subject no longer hears
it, then held in air next
to ear
NORMAL
Hears equally on both
sides
Conduction
deafness
(one ear)
Sound louder in diseased Vibrations in air not
ear because masking
heard after bone
effect of environmental conduction is over
noise is absent on
diseased side
Nerve
deafness
(one ear)
Sound louder in normal
ear
Hears vibration in air
after bone conduction
is over
Bone conduction better
than normal
(conduction defect
excludes masking
noise)
Vibration heard in air Bone conduction worse
after bone conduction than normal
is over, as long as nerve
deafness is partial
C. Audiometry.
An audiometer is an electronic instrument used in medical clinics to test for hearing loss. An
ear specialist uses it to chart an “audiogram”, by means of which certain defects in hearing
can be detected. An instruction manual usually accompanies the audiometer. Test the
audiotory acuity of several members of the class: Starting with high-piched sounds /8000 Hz/,
determine the number of decibels required for the subject to first hear the sound. From
“normal” values: plot the hearing loss /in decibels/ at frequencies from 8000 Hz in descending
steps of 2000 Hz. Below 1000 Hz try 500, 250, and 125 Hz. Test right and left ears
separately. When the plotted points are connected, you have an “audiogram” /see audiogram
chart/.
Audiogram.
Name _______________________________________________________
Age _________ Sex _________ Date ____________Time _____________
Job location __________________________________________________
-10
0
HEARING LEVEL IN DECIBELS
10
20
30
40
50
60
70
80
90
100
110
120
250
500
750
1000
1500
2000
3000
4000
6000
8000
TONE FREQUENCY (Hz)
Examiner________________________ Signature _____________________
Symbols:
Ear
Left
Right
Response
X
O
Phone
Blue
Red