How would you describe Glaucoma to:
i. Another colleague? (2)
- Glaucoma is a progressive condition that results from damage to the optic
nerve, the main nerve which transmits visual information to the brain, which
is primarily due to increased intraocular pressure from the build up of fluid in
the anterior portion of the eye. The condition has a relatively slow onset and
is commonly asymptomatic in the early stages, with the main symptom being
narrowing of the peripheral field of vision. Early diagnosis and treatment are
critical to preserve vision.
1) How would you describe Glaucoma to:
ii. the patient? (2)
- Glaucoma is a condition which affects the nerve at the back of the eye which
is responsible for carrying information about what we are seeing to the brain.
It slowly affects the outside of your vision and then gradually works its way
inwards, like if you imagine going through a tunnel which keeps getting
narrower. This happens when there is too much fluid in the front part of your
eye which causes the pressure inside the eye to get higher, and damages the
nerve. Regular check-ups, monitoring and treatments are important to
prevent the vision from getting worse.
How would you describe Cataract to:
i. Another colleague? (2)
The crystalline lens is mostly responsible for focusing light rays on the back of
the eye correctly, and when it becomes cloudy or opacities develop due to
factors such as ageing mostly, this is termed as a cataract. The cloudy patches
in the lens block or scatter the light from entering the eye which leads to
visual symptoms such as blur, foggy vision, reduced contrast sensitivity, glare
and increased difficulty driving at night. This can eventually lead to blindness,
however if detected, they can be surgically removed and replaced with an
intraocular lens implant to help restore vision again.
b) How would you describe Cataract to:
ii. the patient? (2)
There is a part in your eye which is like a clear window called a lens which
helps you focus your vision, similar to when you try to take a picture with a
camera and you have to focus it first. This lens can become cloudy or develop
patches due to ageing and sometimes other factors, which is termed as a
cataract. This may even appear yellowish in color, and it makes it hard to see
as it can make your vision blurry or foggy, and it can be particularly hard to
see at nighttime or in brightly lit environments. It usually gets worse over
time, however, once detected there is an option to have it surgically removed
and replaced with an artificial lens to help you see clearly again.
c) How would you describe colour issues (in reference to above ocular pathology) to:
i) another colleague? (4)
d) How would you describe what Contrast Sensitivity is to:
i. another colleague? (2)
- The ability to distinguish between an object and its background, particularly
when they vary in different shades, can be described as contrast sensitivity.
Unlike visual acuity which assesses how clear your vision is at a certain
distance, contrast sensitivity assesses how well you can see under lowcontrast conditions or in various different lighting conditions. Spatial
frequencies make up contrast sensitivity, where low frequencies relate to
broader more coarse images where you can see the overall shape of
something but it is not well defined. On the other hand, high special
frequencies capture fine details and sharp edges. Contrast sensitivity
impairment can cause difficulties in everyday tasks such as driving at night or
reading in a dimly lit environment.
d) How would you describe what Contrast Sensitivity is to:
ii. the patient? (2)
- Contrast sensitivity is a measure of how well you can see objects in
comparison to their background. This is especially important to consider in
situations where lighting is not ideal, which makes the difference between
different shades of light and dark more subtle. For example, in foggy weather
you may struggle to see a building in comparison to the background, or in
dark conditions you may struggle to drive. You also may experience difficulty
seeing objects which require extra fine-detail, such as pouring liquids into
cups or recognising faces.
a) How would you describe Wet Macular Degeneration to:
iii. Another colleague? (3)
Age-related macular degeneration (AMD) is an eye condition that leads to the
loss of central vision due to damage to the macula, the central part of the
retina that is responsible for detailed, sharp vision. Wet AMD occurs when
abnormal blood vessels grow under the retina and macula. These fragile
vessels leak fluid or blood which cases damage to the macular tissue and
therefore, leading to a sudden disruption of central vision. This differs from
dry AMD where the blood vessels are not leaking anymore and this is a more
gradual progression in the loss of vision.
a) How would you describe Wet Macular Degeneration to:
iv. the patient? (3)
- Macular degeneration is a condition that affects the central part of your vision,
the part where you see straight ahead. It is more common in older people, and is
caused by age-related changes in the eye. There are two types of AMD which
categories which stage of the condition the eye is at, which are dry AMD and wet
AMD. In wet AMD, new abnormal blood vessels start growing underneath the
layers of the back of the eye, where the signals get sent to the brain in order to
tell us what we are seeing. Due to the abnormal blood vessels being fragile, they
leak fluid or blood which causes swelling and damage to this area, leading to
sudden loss of vision in the center area that controls clear, sharp and central
vision.
b) On review of the current prescription, case history and your own knowledge what
could be done to improve near visual acuity when reading in the house?
i. Optically (2)
(A 81-year-old man attends for his post-op assessment following surgery. On assessment it is
found that the patient has bilateral geographical atrophy following a previous episode of
wet macula degeneration. You are given the details as follows:
R: +0.50/+1.50x170 VA 6/60 ADD +2.50 N36
L: +0.50/+1.25x180 VA 6/120 ADD +2.50 C/F)
The patient has currently been prescribed with a +2.50DS reading add,
however to increase near visual acuity we could increase this to for example,
+3.50DS / +4.00DS which might offer more clarity for near tasks
- Single vision glasses would need to be prescribed for this, as the maximum
add for varifocals is +3.00DS.
- The working distance would have to be closer to the face for this, at
approximately 25cm.
- A magnifier or low vision aid can be given if the increased reading add is not
tolerated, which will have to be trailed to see which one suits the patient the
most
b) On review of the current prescription, case history and your own knowledge what
could be done to improve near visual acuity when reading in the house?
i. Non-Optically (4)
(A 81-year-old man attends for his post-op assessment following surgery. On assessment it is
found that the patient has bilateral geographical atrophy following a previous episode of
wet macula degeneration. You are given the details as follows:
R: +0.50/+1.50x170 VA 6/60 ADD +2.50 N36
L: +0.50/+1.25x180 VA 6/120 ADD +2.50 C/F)
- By increasing the lighting, this can improve reading ability especially if
experiencing problems with reduced contrast sensitivity. It is important
however, to had the additional light (e.g. floor lamp) positioned so that it is
coming from behind and not directly in front, as this can cause glare. Warm
lighting would also help with the glare issue too. - Increased text-size and increased contrast settings if using a device which
allows you to change this, or a specially adapted book if reading which has
implemented this already, which improves readability. - Sensory substitution like voice-controlled tech e.g. text to speech or using
bumper stickers can help with everyday tasks which may be more difficult
with reduced near vision, such as reading the temperature setting of an oven. - Using colour filter overlays can help with reduced colour contrast sensitivity,
which can make it easier to read, for example a yellow overlay. - Large button devices, e.g. telephones with larger buttons so the numbers are
easier to read, or keyboards with bigger letters so its easier to see the letters
to type
c) The patient has been given a leaflet on the Certificate of Visual Impairment (CVI).
They have been advised that they are being referred to Ophthalmology with a view
of registration as visually impaired.
i) Based on ONLY the information above which category would this patient be
registered as? Justify you answer (3).
R: +0.50/+1.50x170 VA 6/60 ADD +2.50 N36
L: +0.50/+1.25x180 VA 6/120 ADD +2.50 C/F)
Based on only the patients VA with correction, the patient would likely be
registered as sight impaired (partially sighted) as the VA is between 6/60 and
3/60 in the better seeing eye (right eye)
- To be registered as severely sight impaired, with 6/60 VA in the better seeing
eye, the patient would also have to be experiencing a severe reduction of
field of vision or a very reduced field of vision especially if a lot of sight is
missing in the lower part of the field.
ii) Which additional piece of information is required to allow for correct
categorisation and what impact would it have (3)?
- The extent of the patient’s field of vision would be an important additional
piece of information, which can be tested with a visual field test. - This is especially relevant as we know the patient has AMD and is
experiencing geographical atrophy which can be affecting his field of vision. - If this was the case, and there was a severe reduction of the field of vision or
a very reduced area of vision is missing, for example the lower part of the
field, then the classification would be severely sight impaired. If the visual
field was full then the patient would be classed as sight impaired (partially
sighted). - The impact of this is that severely sight impaired individuals are eligible for
more extensive financial support and may be able to access higher benefits
such as 50% off television license fee and automatic blue badge parking
permit. They may have access to more comprehensive mobility aids such as
guide dogs and white canes too.
ii) What are the benefits to the patient of being registered with a visual
impairment? (2)
- There are welfare benefits such as financial help, railcards and other travel
concessions, free postage, and other useful services such as RNIB talking
books. You also get protection under the Equality Act 2010. - There are healthcare and social care advantages such as free NHS eyesight
tests and social care visits to assist you further.
A.1 Define low vision
- A visual impairment that is not correctable through surgery, pharmaceuticals, glasses, or contact lenses.
- Characterized by partial sight, such as blurred vision, blind spots or tunnel vision, but also includes legal blindness.
- Low vision can impact people of all ages, but it is associated primarily with adults over the age of 60.
A.4 Understand the criteria for referral for a new prescription and understand limitation of knowledge.
A.7 Describe the factors affecting contrast sensitivity and the clinical tests used to assess it.
What is Contrast Sensitivity?
Ability to distinguish between an object and the background behind it.
Different fromvisual acuity, which measures how clear your vision is at a given distance.
High spatial frequencies make up detailed features such as sharp edges, facial features, and similar.
Low spatial frequencies are more like coarse images, where you can see the overall shape of something but not detailed features.
How is Contrast Sensitivity measured?
Test chart where the characters gradually fade from black to grey.
Visual acuity is measured when you read the eye chart during an exam. This is considered ahigh contrasttest (black letters on a white background).
You can have excellent visual acuity, but reduced contrast sensitivity and vice versa.
What effects Contrast Sensitivity?
Glaucoma
Cataracts
Amblyopia
Age-related macular degeneration
A.11 Understand the reasons for reduced near vision acuity.
Cataract
Macula Degeneration
Glaucoma
A.13 Be aware that systemic pathology may affect vision, visual acuity and visual fields. Cataract and glaucoma
What is Cataract?
When the lens, a small transparent disc inside your eye, develops cloudy patches.
Over time these patches usually become bigger causing blurry, misty vision and eventually blindness.
What is Age-Relate Macula Degeneration?
“an eyedisease thatcanblur your central vision”
Aging causes damage to the macula
Part of the eye that controls sharp, straight-ahead vision
@@@@@@@DRY VS WET@@@@@@@
What is Glaucoma?
“Condition where the optic nerve, which connects the eye to the brain, becomes damaged”
It’s usually caused by fluid building up in the front part of the eye, which increases pressure inside the eye.
Can lead to loss of vision if it’s not diagnosed and treated early.
A.15 Understand the method of paraxial ray tracing through a thick lens or system of lenses, including telescopic systems and calculate magnifying power in afocal and non-afocal settings.
A.30 Explain the use of specialist viewing techniques and calculate how a single thin lens could replace this system of lens.
How do we make the image bigger?
Increase object size (electronically or bigger buttons)
Alter the Contrast
Decrease viewing distance (move closer to TV)
Move the position of the image (VF loss)
Eccentric Fixation (When the patient uses a point on their retina which is not the fovea to allow then to see a target)
6.1.1 Considers the effectiveness of current refraction of patients with low visual acuity and to refer back where appropriate
6.2.1 Understands the assessment of visual function, including the use of specialist charts, the effects of illumination, contrast and glare
Preferrential looking- VA, different spaical freqeuncies,
Visual Acuity
Colour vision
Stereopsis
What is contrast?
“the state of being strikingly different from something else in juxtaposition or close association”
What is Contrast Sensitivity?
“The ability to distinguish between an object and the background behind it”
Why is Contrast Important in the assessment of visual function?
Visual Acuity can be fine but patient still cannot see clear
Real life vision
Driving at night is an example of an activity that requires good contrast sensitivity for safety.
What is illumination?
“deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight”
Daylight Light Bulb
Aim to position from behind
What is glare?
“loss of visual performance or discomfort produced by an intensity of light in the visual field greater than the intensity of light to which the eyes are adapted”
Distracting and even dangerous
Can occur day or night in a number of ways.
Glare may come directly from a light source or be reflected.
There are four types of glare:
1)Distracting glare (Distracting glare
Results from light being reflected when it moves from one optical medium to another (e.g. from air to glass). This results in some of the light being reflected off the surface, or internally reflecting within a spectacle lens.
Comes from light reflected off the front of lenses so that others can’t see your eyes, and from light reflected off the backs of or within the lenses so that you see reflections in your lenses. Can also be experienced at night, forming “halos” around headlights or streetlights. Can represent an annoyance or distraction to the viewer and lead to eye fatigue.)
2)Discomforting glare (Results from direct or reflected glare and can be caused by everyday, bright sunlight conditions. Occurs in varying degrees of intensity, but even the milder degrees of discomforting glare result in visual discomfort, often shown by symptoms of eyestrain or fatigue. Depending upon one’s light sensitivity, this glare can also be discomforting regardless of weather or time of day. The unprotected eye will respond to discomforting glare by squinting and constriction of the pupil. It is common for the affected individual to try to avoid the glare by shielding the eyes or turning another direction).
3)Disabling glare (Disabling glare, also known as veiling glare, is more intense than discomforting glare and the high level of light produces a glare that can actually interfere with or block vision. This type of glare comes from excessive, intense light that can occur when you face directly into the sun. Causes objects to appear to have lower contrast than they would if there no glare. Light scatters when it enters the eye, which, in turn, reduces the sharpness of vision and raises the differential light threshold. More problematic in the elderly, as the decreasing transparency of the crystalline lens that comes with age leads to developing cataract formation).
4)Blinding glare.
Blinding glare results from light reflecting off of smooth, shiny surfaces such as water, sand or snow. It can be strong enough to block vision. When the light reflects of the surfaces, it becomes polarized and produces blinding glare. Patient becomes visually compromised.
Tends to be worse with:
Older age
Light coloured eyes
Prior eye surgery
Certain eye conditions, includingCataracts, Dry Eye andMacular Degeneration.
Treatment options:
Shielding of eyes
Sunglasses – Polaroids
Breaks
Dimming of Lights
