Usher Syndrome
Clinical Assessments
This document covers all of the clinical assessments used in the
National Collaborative Usher Study (NCUS).
Vision assessments
Before the eye examinations begin, the person assessing you
(usually an ophthalmologist) will ask:
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Whether you are having any trouble with your vision
Whether you have noticed any change with your vision
Whether you are on any medication
The medical background of your family particularly hereditary eye
conditions, diabetes and high blood pressure
This is to highlight any key points that the ophthalmologist should
look out for or test further.
Positioning
In general, most eye examinations require the individual to be sat
stationary in a chair whilst resting their chin on a chin rest and with
their forehead resting against a support strap. Despite the positioning
of the individual being similar in most cases, the actual machinery
used for each test is different. The different machines are specialised
for analysing different structures of the eye.
Eye drops
Examinations that assess structures inside the eye usually require
eye drops to be given to the individuals so that the pupils dilate and
the ophthalmologist can then assess more of the inner surface of the
individuals eye i.e. the retina. It takes an average 15-20 minutes for
the eye drops to work. If eye drops are given, someone else will have
to drive you home and excessive sunlight should be avoided. Your
vision, particularly near vision and ability to focus, will be slightly
blurred for up to 12 hours after the eye drops are administered. Also,
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if your family has a history of glaucoma then it is important that you
tell the examiner if eye drops will be used.
Always try and find out what assessments will be carried out during
your appointment so you can prepare beforehand.
The above image was taken from the National Eye Institute, National
Institutes of Health (NEI, 2012a). It illustrates the proportion of the retina
that can be seen with an undilated pupil and with a dilated pupil. Eye drops
are given so that the examiner can assess more of patient’s retina.
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The eye examinations used for the NCUS study were:
Best corrected visual acuity
Why the test is carried out
An individual’s visual acuity is assessed to determine the ‘sharpness’
of their vision. This test is routinely carried out by optometrists at an
opticians store such as specsavers; ophthalmologists also perform
this test at the eye hospitals prior to an appointment.
There are various forms of this eye exam; however, they generally
involve a chart displaying 11 rows of capital letters, known as the
Snellen eye chart. The font size decreases in size when reading the
chart from top to bottom. There are new devices that can assess your
vision in the same way as a Snellen chart.
How to prepare for the test
Avoid strain on the eye prior to the test.
The image above is from the MedlinePlus, National Institute of Health.
It shows a man having a visual acuity assessment
(MedlinePlus, 2012a).
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How the assessment is carried out
i. The individual sits in a chair 20 meters away from the chart.
ii. The individual is then asked to read the smallest line of letters they
can see.
iii. The examiner may then give the individual lenses of various
strengths to see if vision improves or worsens. If it improves, you
may need to wear glasses.
In addition to assessment with the Snellen chart, the ophthalmologist
may quickly assess other parts of your eye:
Shining a penlight on your pupil will show whether your pupil is able
to respond to light properly [NIH].
Making you look in different directions whilst keeping your head still
will assess your eye muscles [NIH].
Asking whether you can see specific objects at the side of your vision
will assess your peripheral vision [NIH].
Slit lamp biomicroscopy
Why the test is carried out
This form of microscopy enables the examiner to assess both the
outer surface and inner surface of the eye.
The outer surface structure being assessed is the cornea and lens.
When assessing the inner surface structure, the retina, the examiner
also uses an additional lens. It is help between the slit-lamp and the
patient’s eye. Frequently, the examiner gives the patient eye drops to
widen the pupil.
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The above image is from MedlinePlus, National Institute of
Health (MedlinePlus, 2012b). It shows a woman having her
eye assessed with a slit lamp microscope2.
How to prepare for the test
Tell the examiner if you are currently on medication or whether you
have an allergy to a particular medication. Also, if your family has a
history of glaucoma then it is important that you tell the examiner prior
to the eye drops being administered.
How the test is performed
This assessment is carried out via the following steps:
i. The individual sits in a chair.
ii. The ophthalmologist places eye drops in the individual’s eye to
dilate the pupil. The eye drops take an average of 15-20 minutes
to work.
iii. The microscope, which is placed on a table, is adjusted so that it is
positioned in front of the individual.
iv. The individual then positions their head according to the chin rest
and forehead strap, supporting them in keeping their head still
during the assessment.
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v. Using the slit-lamp microscope as well as a handheld lens, held
near the patient’s eye, the examiner begins to assess the inside
surface of the eye.
In some cases, the examiner may want to assess the white surface of
the eye and the tear layer. If so, the following steps are taken:
i. An eye drop containing a dye or a fine strip of paper stained with a
dye may be applied to the white surface of the individual’s eye.
ii. The individual is then asked to position themselves according to
the chin and forehead rest attached to the microscope, as
previously done.
iii. The examiner then uses the slit lamp to analyse the surface
further.
iv. The dye is washed out via blinking.
Hardy-Rand Rittler colour plates
Why the test is carried out
The Hardy-Rand Rittler (HRR) colour plates is a test designed to
detect, classify and estimate the degree of defective colour vision,
specifically the colours red, green, yellow, and blue for both
congenital and acquired defect testing as well as positive
classifications of individuals with standard colour vision.
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The above image is taken from Gulden Ophthalmics (Gulden
Opthalmics, 2012). It is an example of the HRR colour plates used
to test colour vision.
How the test is performed
The HRR colour plates are made up of coloured circles in the
background in a range of sizes and lightness. These plates test for
red, green, yellow, and blue colour vision, with some plates being
more difficult for others; this helps examine, if present, the severity of
colour vision defect.
This assessment is carried out via the following steps:
i. The individual is sat in a chair.
ii. The examiner then presents a plate to the individual.
iii. The individual then tells the examiner what they can see
iv. This is repeated until all of the colour plates have been presented.
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Goldmann perimetry
Why the test is carried out
Goldmann perimetry is a test that assess an individual’s visual field
sensitivity. Since the results of the test is not analysed using a
computerized system, the accuracy is dependent on both the
individual and the examiner. It is important that the individual fully
understands the test, maintains fixation on the point of focus and
responds appropriately.
How to prepare for the test
Avoid strain on the eye prior to the test.
How the test is performed
This assessment is carried out via the following steps:
i. The individual is sat in a chair with the apparatus placed directly in
front of the individual.
ii. A patch is worn on the eye not being examined.
iii. The individual then positions their head according to the chin rest
and forehead strap.
iv. The room lighting is then turned off.
v. Once the individual is staring at a fixed spot, a moving stimulus
(the stimulus chosen depends on the examiner as it could be a
flashing light) is presented to the individual in different regions of
their visual field. Initially, the peripheral visual field is assessed,
and then the central visual field is tested. This stimulus is
controlled by the examiner.
vi. After each stimulus, the individual informs the examiner whether or
not they saw the stimulus presented by pressing a buzzer or giving
a verbal response.
vii. The examiner then records the individual’s responses on paper in
the form of a ‘visual map’.
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This ‘visual map’ illustrates the individual’s peripheral and central
visual field sensitivity boundary. Assessment of each eye should not
take longer than 10 minutes to avoid straining of the eye.
The above image is from MedlinePlus, National Institute of Health
(MedlinePlus, 2012c). It shows a woman having her visual field
assessed.
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Retinal imaging
There are a few specialised cameras that are able to capture images
of the interior surface of the eye.
a) Digital colour fundus photography
Why the test is carried out
Digital colour fundus photography is a form of eye examination that
captures a coloured picture of the interior surface of the eye i.e. the
retina. It is usually used to accurately document what is seen with the
slit-lamp microscopy. This apparatus is made up of a specialized low
power microscope with a specialized camera attached. It is used for
the diagnosis of a condition (alongside retinal angiography
(described below)) as well as for monitoring the progression of a
condition.
How to prepare for the test
Avoid driving to your appointment as you will be given eye drops for
your assessment; try and bring someone with you if you need to
travel by vehicle. If you plan to go back to work, keep in mind that you
will not be able to handle heavy machinery as you will not be able to
focus your vision for up to 12 hours. If the individual has a family
history of glaucoma, notify the examiner prior to the eye drops being
administered.
If the individual is pregnant and will be having a retinal angiography
assessment (see below) the ophthalmologist must be informed.
How the test is performed
This assessment is carried out via the following steps:
i. The individual sits in a chair.
ii. The ophthalmologist places eye drops in the individual’s eye to
dilate the pupil. The eye drops take an average of 15-20 minutes
to work.
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iii. The individual then positions their head according to the chin and
forehead rest, supporting them in keeping their head still during
the assessment.
iv. The apparatus is then positioned correctly in front of the individual,
focusing on the target eye.
v. Images can then begin to be captured.
Retinal angiography involves the use of the digital colour fundus
camera following the same steps as above; however, a coloured dye
(called fluorescein), is administered via an injection into the arm of
the individual prior to images being captured. Once administered, a
series of pictures are captured to see the flow of blood through the
retina and choroid (these structures are layers at the back of the eye).
The dye induces a high contrast between the vessels and the retinal
tissue, highlighting not only proper circulation in the retinal vessels
but also any abnormalities such as the growth of new blood vessels
in the macula (central region of the retina that is responsible for sharp
detailed colour vision and does not have any blood vessels present),
leakage from the retinal vessels or blockage.
The individual’s urine will change colour, it will become more orange.
This may last a day or two after the test and is nothing to be alarmed
about. This is the dye leaving the individuals body.
b) Optical coherence tomography (OCT)
Why the test is carried out
The aim of the OCT is to capture micrometer resolution, threedimensional images of both the front and back of the eye.
OCT enables the examiner to assess the different layers of the retina
and to measure the overall thickness of the retina. This is important
when determining or monitoring the extent of photoreceptor
degeneration.
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How the test is performed
This assessment is carried out via the following steps:
The individual sits in a chair.
The individual then positions their head according to the chin and
forehead rest, supporting them in keeping their head still during the
assessment.
Images can then begin to be captured.
Fundus autofluorescence (FAF)
Why the test is carried out
FAF is a specialised camera that specifically monitors natural
autofluorescence (absorbed light) in specific parts of the retina. High
levels of autofluorescence may indicate degenerative change or
injury, whilst low levels may indicate missing or non-functional retinal
cells. This assessment is effective in confirming or eliminating agerelated macular degeneration (AMD) as a diagnosis. This
assessment is relatively similar with most eye examinations involving
microscopes, in terms of the preparatory steps.
How to prepare for the test
Tell the examiner if you are currently on medication or whether you
have an allergy to a particular medication. Also, if your family has a
history of glaucoma then it is important that you tell the examiner prior
to the eye drops being administered.
How the test is performed
This assessment is carried out via the following steps:
1. The individual sits in a chair
2. The individual then positions their head according to the chin
and forehead rest, supporting them in keeping their head still
during the assessment.
3. The examiner will then shine a blue light in the patient’s eye
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4. Images can then be captured and the flow or fluorescence is
then measured.
Electroretinograms (RGSs)
Why the test is carried out
Electroretinograms measure the electrical activity of the lightsensitive cells in the retina, called photoreceptors in response to a
light stimulus. It detects disorders of the retina. There are two types of
photoreceptors, these are rods and cones.
How the test is performed
This assessment is carried out via the following steps:
i. Eye drops are administered to prevent the individual feeling any
discomfort.
ii. The individual’s eye is held open with a device called a retractor;
this will make sure the examination is completed successfully.
iii. Electrodes are placed on the cornea and the skin near the eye.
iv. The individual’s eyes are exposed to a visual stimulus (light
source).
v. The electrodes record the electrical activity triggered by the stimuli,
which is displayed in a graph format.
This assessment is carried out, initially in a normally lit room and then
the individual is taken into a dark room, given 20 minutes to adjust,
and then the examination is carried out again following the same
steps.
In total, this assessment takes up to an hour to complete.
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Hearing
Various audiometric tests were used to assess hearing in the NCUS
participants.
The tests carried out were:
Pure tone audiometry (PTA)
Why the test is carried out
A PTA is more commonly known as a hearing test and is used to
identify a persons hearing thresholds. Different sounds are played at
different volumes through headphones and a bone conductor
(another type of headband). This enables the examiner to determine
the degree, type and configuration of a hearing loss, providing the
basis for diagnosis and management.
How the test is performed
This assessment is carried out via the following steps:
i. The individual sits in a chair facing away from the equipment and
has headphones placed over their ears.
ii. The audiologist then presents sounds of decreasing volume
through the headphones.
iii. Once the individual hears the sound, they must then press a
button or raise their finger and hold it until they can no longer hear
the sound.
iv. Once the testing using the headphones is complete a second
headband may be used to test in the same way but for less
number of sounds. This is called a Bone Conductor (BC) and is
placed behind the ear.
A PTA is often performed using a computer, however the computer
does not analyse the results so a patient’s response is crucial. It is
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important that the individual fully understands the test and asks
questions if they are at all unsure.
A hearing test takes approximately 30 minutes to complete.
Tympanometry
Why the test is carried out
Tympanometry is not a hearing test, but rather a measure of the ear
drum. The ear drum this is the membrane that separates the ear
canal from the middle ear. The test measures how the ear drum
moves in response to variable air pressures, introduced into the ear
canal via the tip of the device. This test assesses middle ear function
and can help the diagnosis of the type of hearing loss.
How the test is performed
This assessment is carried out via the following steps:
i. The individual sits in a chair.
ii. An appropriate sized probe tip is inserted into the ear canal to
create an acoustic seal.
iii. Variable air pressure is introduced into the ear canal via the probe,
this can cause a slight blocked feeling during the test.
iv. Ear drum mobility is then automatically recorded in the form of a
graph called a tympanogram. The final graph produced would then
illustrate the overall functioning of the ear drum.
Tympanometry takes a few minutes to complete.
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Stapedial reflex measurement
Why the test is carried out
The stapedial reflex is an involuntary contraction of muscles in the
middle ear, in response to a loud sound. This reflex occurs in both
ears at the same time and can be measured in either one ear or both.
The stapedial reflex response can help to confirm where the hearing
problem is located by activating earlier than normal, later than normal
or by not being present at all.
How the test is performed
This assessment is carried out via the following steps:
i. The individual sits still and in silence.
ii. A probe, the same as the one used for tympanometry, is placed in
the ear that is going to be tested.
iii. Another probe may be placed in the other ear, this depends on the
type of test being performed.
iv. Often, audiologists perform tympanometry first (See above). If not,
they go straight to step 5.
v. The audiologist presents sounds of varying volume for 1-2
seconds in duration.
vi. Once a reflex is detected via the probe, the examination ends.
Together tympanometry and stapedial reflex measurements take
approximately 5 minutes to perform.
Transient evoked otoacoustic emission recordings
(TOAE)
Why the test is carried out
Otoacoustic emissions are sounds that are generated in the cochlea,
part of the inner ear. The cochlea contains inner and outer hair cells
that react when a sound vibration is received, the reaction of the cells
normally send messages to the brain via the basilar membrane and
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the auditory nerve indicating that a sound has been heard. A TOAE is
able to record certain activity that takes place in the cochlea when it
responds to sound. The assessment can be carried out on individuals
who are asleep or even babies, as a behavioural response is not
required.
How the test is performed
This assessment is carried out via the following steps:
i. An appropriate sized probe tip is inserted into the ear canal to
create an acoustic seal.
ii. Brief click sounds are presented to the ear through the probe.
iii. Otoacoustic emissions are recorded via the microphone
embedded in the probe.
The probe creates an acoustic seal in the ear canal in order to
maximise the capture of the otoacoustic emissions and eliminate
background noise. A microphone within the probe detects the
otoacoustic emissions.
A present OAE confirms cochlear function is normal. It does not
confirm if a sound can be heard or processed by the individual. The
auditory nerve could be damaged or firing dyssynchronously yet the
OAE would be normal.
The test is completed for both ears in a few minutes.
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Balance
Vestibular function (balance) was assessed in the NCUS
participants via the following tests:
Infrared video nystagmography (VNG)
Why the test is carried out
This form of assessment records involuntary eye movements, called
nystagmus, in a video format; enabling the examiner to carry out an
analysis and determine whether or not the dizziness is due to an
inner ear disorder.
How the test is performed
This assessment is carried out via the following steps:
i. The individual is given hi-tech video goggles with infrared cameras
to wear, in order for eye movements to be recorded and assessed.
ii. Once worn, the individual is then asked to look or lie in different
positions according to the specific VNG assessment being carried
out.
i. Saccade test: evaluates rapid eye movement.
ii. Tracking test: evaluates movement of the eyes as
they follow a visual target.
iii. Positional test: measures dizziness associated with
the position of the head.
iv. Caloric test (sometimes called ENG): measures the
individual’s response to the presence of warm and
cold water in the ear canal via a soft tube.
iii. The hi-tech goggles are connected to a display screen which
shows the recorded eye movements of the individual.
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Rotary chair system
Why the test is performed
The rotary chair system is designed to assess the vestibulo-ocular
reflex (VOR), which is a reflex whereby eye movement is fixed on an
image during head movement, maintaining the image at the centre of
the retina. Therefore, eye movement is opposite to head movement.
In the case of individuals suffering from dizziness, this assessment
can determine whether or not the cause is due to a problem with the
inner ear. If not, the cause must be associated with a disorder of the
brain. Head movement during this assessment is caused by the
rotating chair.
How the test is performed
This assessment is usually carried out in a lightproof room that has a
2-way communication system so the individual can be in constant
communication with the examiner. Eye movement is assessed via the
use of electrodes or by the use of an infrared camera, which is placed
directly in front of the individual. It is important that the individual
keeps their eye constantly open.
This assessment is carried out via the following steps:
a) The individual sits in the chair with their head secured in one
position.
b)If electrodes are used:
c) Electrodes are placed on the skin of each eye (the corner
where the upper and lower eyelids meet) and an additional
electrode is place on either the forehead or the earlobe.
d) The electrodes are then connected to a computer.
e) If an infrared camera is used then step 4 is carried out instead
f) Assessment can then begin.
g) Results are assessed either by the recordings from the
electrode or via the video recorded by the infrared camera.
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References
Gulden Ophthalmics (2012). HRR-Pseudoisochromatic-Plates.
Gulden Ophthalmics. Available via
http://www.guldenophthalmics.com/ccp7/HRR-PseudoisochromaticPlates [Accessed 22/09/2012].
MedlinePlus (2012a). Visual Acuity Test. National Institutes of Health.
Available via
http://www.nlm.nih.gov/medlineplus/ency/imagepages/1124.htm
[Accessed 21/09/2012].
MedilinePlus (2012b). Slit lamp exam. National Institutes of Health.
Available via
http://www.nlm.nih.gov/medlineplus/ency/imagepages/1140.htm
[Accessed 22/09/2012].
MedlinePlus (2012c). Visual Field Test. National Institutes of Health.
Available via
http://www.nlm.nih.gov/medlineplus/ency/imagepages/1143.htm
[accessed 23/09/2012].
NEI (2012a). Information for healthy vision: What is a comprehensive
dilated eye exam? National Institutes of Health. Available via
http://www.nei.nih.gov/healthyeyes/eyeexam.asp [Accessed
01/10/2012].
Stabej PLQ, Saihan Z, Rangesh N, Steele-Stallard HB, Ambrose J,
Coffey A, Emmerson J, Haralambous E, Hughes Y, Steel KP, Luxon
LM, Webster A, Bitner-Glindzicz M (2012). Comprehensive sequence
analysis of nine Usher syndrome genes in the UK National
Collaborative Usher Study. J Med Genet 2012; 49:27-36.
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This document was produced by:
Yemi Tadesse
Research Officer
Telephone: 02070149369
Email: [email protected]
Sense, 101 Pentonville Road, London, N1 9LG.
The ‘Hearing’ section of this booklet was also produced by:
Donna Corrigan
Technology Co-ordinator
Email: [email protected]
Sense, 101 Pentonville Road, London, N1 9LG.
Please do contact us if you have queries in regards to, visual,
hearing and balance assessments.
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