Low Vision Flashcards
possible referral pathways and what info needs to be given
- You observe findings which cannot be managed within your scope of practice, and you should refer the patient to an appropriate practitioner
- Emergency = same day = contact ARC / on-call / triage nurse / switch board; patient takes letter in hand to HES
- Urgent = 2-4 weeks = SCI gateway
- AMD rapid access
- Routine = 6+ months = SCI gateway
- Private = Rosshall BMI, Nuffield, Ayrshire eye clinic
Reason for referral, images if appropriate
Details of discussion with patient
Level of urgency
examples of emergency same day referrals
➢ AACG
➢ Chemical Injuries
➢ CRAO
➢ Hyphaemia
➢ Hypopyon
➢ IOP> 45mmHg
➢ Orbital cellulitis
➢ Papilloedema
➢ Penetrating injuries
➢ Retinal Detachment
➢ Sight threatening Keratitis
➢ Sudden severe ocular pain
➢ Suspected temporal arteritis
➢ symptomatic retinal tear
➢ 3rd CN Palsy and pain
➢ unexplained pre-retinal haemorrhage
➢ unexplained sudden loss of vision
➢ uveitis
➢ vitreous detachment with pigment in vitreous
Urgent Referral (1 week) examples
Acute dacrocystitis
* Candida retinitis
* CRVO with raised IOP
* Disc Haemorrhage in Px without glaucoma ➢ IOP >35 but <45, RD macula off
* Retrobulbar optic neuritis
* Rubeosis
* Scleritis
* SCC
* sudden onset diplopia
* Wet AMD/ CNV according to local fast track protocol
Disability and Equality Act (2010):
Patients should be treated equally and prevented from discrimination (e.g. in education, employment, good service, facilities, transport).
For Optometrists:
* Provide the same level of care.
* Adapt your routine to accommodate a patient.
* Allow them to access the facility
You are disabled under the Equality Act 2010 if you have a physical or mental impairment that has a “substantial” and “long term” negative effect on your ability to do normal daily activities.
“Substantial” = more than trivial, e.g., takes longer than it usually would to complete a daily task such as getting dressed
“Long term” = longer than 12 months.
You automatically meet the disability definition and are protected under the Equality Act if you have cancer, HIV or MS
Different Types of Disabilities
Physical – Amputation, Motor Neuron Disease, Advanced MS
* Sensory – Blind or Deaf
* Intellectual – Dyslexic, Dementia, Down Syndrome
* Emotional – Anxiety or Depression
* Developmental – Autism
what is RVI – Registration for Visual Impairment
This form will:
tell social services about your situation
request an assessment of your need for support
state how urgently they think you require help, so you do not have to wait until the end of your treatment at the clinic to be referred.
what is the LVL - low vision leaflet
Low vision leaflet
Issued by optom
Allows px to self-refer their visual impairment to social services
It contains information such as px’s daily tasks & responsibilities and their areas of concern.
The LVL leaflet comes with contact details telling you where to get advice and information locally and nationally. As well as giving you this leaflet, your optician can arrange for you to be seen at your local hospital eye clinic by a consultant ophthalmologist.
what is VINCYP - Visual impairment network for children and young people
Different form for under 16s
Visual impairment network for children and young people
Children under 16 are no longer registered
Needs of children with visual impairment differs from adults
National care pathway for local teams to use in their own area
Evidence letter from ophthalmologist, orthoptist, optometrist or visual impairment paediatrician
Benefits – can still apply for benefits by stating the registration system in Scotland does not apply to children under 16 and you are providing alternative evidence (i.e., letter from healthcare professional)
Adaptation of routine for Px with visual impairment
Guiding patient
Start with visions such as hand movements and then move into chart
Test slowly. Be aware that px may only read half the chart (e.g. homonymous hemianopia).
Use large target during cover test, ret etc. to ensure it is seen
Use large changes in lens power – large brackets
Pinhole may be difficult/impossible
Give encouragement during VFs
how to calculate which magnification to to use
use 4 x table
if N16 then started with 4x mag
trial and error
pelli robson chart
Pelli-Robson – Triplet of letters decreasing in contrast, test at 1m – each letter is 0.05. lowest contrast where 2/3 seen determines CS. A score of 2.0 is normal while score below 1.5 suggest impairment
Distance correction worn (add +0.75 onto this if px is Presbyopic to account for 1m distance)
Each triplet of letters is at a different contrast
Must get at least 2 letters from 1 triplet to achieve that score
log MAR chart
Scored by letter (0.02 a letter), crowded and uses Bailey Lovie letters (6m to 3m add 0.3) +0.3 to score for every time the distance from px to chart is halved
Bailey Lovie Letters : Five letters per row, with letter spacing equal to one letter width, and row spacing equal to the height of the letters below.
Logarithmic progression of sizes, increasing in 0.1 logMAR steps for each line
Sight impaired benefits of registering
Disabled person’s railcard
Free telephone directory enquiries
Protection under Equality Act
Universal credit, pension cried, tax credits
Severely sight impaired benefits of registering
As with SI, but also…
Blue badge
50% off TV license
Free postal service
Council tax exemptions (up to £2,290)
Criteria for registration as SEVERELY SIGHT IMPAIRED (SSI)
VA of less than 3/60 (6/120) with full visual field
VA of 3/60 (6/120) – 6/60 with a severe VF reduction (e.g., tunnel vision)
VA of 6/60 or better with very reduced VF, especially if a lot of sight is missing in the lower visual field
Criteria for registration as SIGHT IMPAIRED (SI)
VA of 3/60 (6/120) – 6/60 with full visual field
VA of up to 6/24 with a moderate VF reduction or a central area of blur i.e. opacities/aphakia
VA of up to 6/18 with a large VF defect (e.g., hemianopia)
CVI - certificate of visual impairment
Introduced to Scotland in 2018
CVI is written by a consultant ophthalmologist and determines if the px is sight impaired or severely sight impaired (eligibility is based on VA / VF)
Certificate is called a BP1.
The certificate contains:
o Signature of px consent & consultant’s signature
o Statement if the px is sight impaired or severely sight impaired
o Px details
o Uncorrected vision
o Best corrected VA
o Brief description of any VF loss
o If the px has yet been assessed by the low vision service
o Cause of visual impairment
o Other relevant factors (e.g., does px live alone? Hearing impaired? Poor physical mobility? Other health conditions?)
o Urgency with which the px requires contact/help
LVAs - assistive tech like apps
BlindSquare – App describes environment and announces points of
interests/streets/specified points as you travel
* iDentifi – Voiceovers objects in the camera screen
* Be My Eyes – App matches visually impaired user with sighted volunteer for help
* Kindle
non optical aids for LVAs
- Tints – Dark for albinism or RP, Yellow filters for CS in AMD
- Caps/Visors to reduce excess glare and reflections
- Typoscopes
- Extra Illumination for AMD, Glaucoma, DR, RP
- Reduced illumination for Albinism, Anridia, Cataracts
difference between registration and certification Low vision
Certification
An ophthalmologist completes a Certificate of Vision Impairment (CVI) based on the patient’s visual function and support needs. The CVI certifies the patient as sight impaired or severely sight impaired.
Registration
Patients can voluntarily register with their local social services department after receiving their CVI. Registration makes patients eligible for various benefits and support. Added to your local authority’s register of sight impaired or severely sight impaired people.
other definitions
- functionally blind
- functionally sighted
-functionally sighted with aided mobility
- functionally sighted without sighted literacy
Functionally blind: can’t see to read/write with LVA, cannot move in unfamiliar surroundings without dog/cane
Functionally sighted: VI but can read with LVAs and can move in unfamiliar surroundings without dog/cane
Functionally sighted with aided mobility: VI and can read with LVA or visually identify objects but can’t move in unfamiliar surroundings without dog/can (e.g., RP)
Functionally sighted without sighted literacy: VI, can move in unfamiliar surroundings but cannot read with LVAs (e.g., AMD)
ECLO = Eye Clinic Liaison Officer
- Good and important person for the px to be in contact with
- Provides practical and emotional support to the px (as well as family) suffering from sight loss
- Works in hospital and helps with rehabilitation, guiding, support at home etc.
if px could not read chart and had to be brought closer, how would VA be measured?
if px reverses as far back as possible from the test chair - measure distance from the px to the test chart. Projector and mirror system is differnt. If px at 2m and projector chart, then they would see 4/60 not 6/60, accomodation if 2m away is (1/2) 0.5D. So would correct presciption by 0.50DS (give the minus 0.50DS from rx found)
For mirror chart if px 2m away it would be 5m (since 2m to px and 3m from mirror) so 5/60 rather than 6/60. Would give -0.25DS to the prescription.
lighting needed by low vision px
LV px needs 500-1000 lux
Helps because:
o Reduces scotoma size
o Changes adaptive state of the retina – increases sensitivity (reduces threshold)
o Dying photoreceptors on the edges will be simulated
o Smaller pupil = larger depth of focus
What non optical measures can improve lighting glare etc
Increase lighting
o Angle lamp perpendicular to task
o Bright wall colours
o Clean windows
Increase natural daylight
* Open curtains
* Sit near the natural light but avoid glare and shadows on objects of interest
* Pale wall colour - light reflection but not glossy as can create glare
* Use dimmer switches for controlling the amount of light in the room
* Extra lighting where it could be difficult to move around, such as hallways and stairs
* Aim the light directly on the task at hand.
Reduce glare
o Window blinds
o Lamp shades
o Wrap around sunglasses
o Typoscopes
discomfort glare
reduced by lowering the amount of light hitting the eye.
o Neutral density filters useful – absorbs lights of all wavelength
o Tints also absorb all wavelengths
o Not appropriate for constant use as might require more light indoors
disability glare
reduce the scattered light in the eye, while leaving unscattered light intact.
o Shorter wavelength light scatters more in the eye compared to the longer
wavelength light.
o Filters to absorb short wavelength light is useful for people with visual
impairment.
o Reducing disability glare also improves VA
what type of filters to px’s with AMD prefer
o Loss of contrast sensitivity and glare
o AMD px prefer Yellow and Orange filters over Blue, Brown, etc. -
Improves as it improves CS and VA
glare adverse effects
Immediate effects
Glare can cause immediate discomfort, such as squinting, tearing, or looking away. It can also cause visual fatigue, which can lead to headaches, burning, or increased light sensitivity
blurred/reduced vision
why is contrast sensitivity measured
Contrast sensitivity is a very important measure of visual function, especially in situations of low light, fog or glare, when the contrast between objects and their background is often reduced. Driving at night is an example of an activity that, for safety, requires good contrast sensitivity
- some jobs require it to be normal
can be a symptom of eye conditions like cataract, DM, glaucoma, AMD
common causes of VI
Common cause of VI
Children - optic atrophy, cataracts, nystagmus
Early adult life: stargardt’s, AMD, RP
Working years: DR, myopia, corneal dystrophies
Retirement: cataract, AMD
Others: RD, glaucoma, myopic degeneration
hand held magnifers, instructions, adv and dis
Instructions:
Distance Rx worn for longer mag-eye distance (light leaving magnifier is parallel)
Lay magnifier on page & slowly pull-away from page until image clear
To improve FoV; move eye closer
Possibly need near rx if short mag-eye distance being used (for wider field of view)
Should be held parallel to reading material
Move head & magnifier as a unit together
If px says hand magnifier is not strong enough; best option is to tell them to move the lens & object closer to their glasses
Portable & lightweight
No flat surface required
Socially acceptable
Inexpensive
Wide range of mags
Distance rx needed (confusing)
Requires steady hand & fixed WD
Limited FoV
stand magnifier
Instructions:
Ensure flat surface
Use tracking strategies – use card to follow a line
Near rx required (light leaving magnifier is divergent – when focal length is less than f1)
Better for poor dexterity px’s (arthritis, parkinsons)
Logical – SVN required
Can be written under if required e.g. crosswords
Wide range of mags available
Require flat surface
Heavy / bulky
Limited FoV
Posture & fatigue problems
spectacle mounted telescope LVA
Used for prolonged reading, wide FoV
May be useful for px’s with hand tremors
Reduced reading speed as very close WD
Blurred DV
Not likely to work if >+12.00
Hands free; useful for pronged reading
Worst field of view (shortest eye-mag distance)
Cosmesis
Can incorporate astigmatism
Close WD
o Illumination difficult
o Fatigue, HAs, dizziness
o Binocularity/convergence problems (over +12D)
Galilean telescopes
Galilean telescopes are made up of 2 lenses.
The objective lens is a convex (plus) lens (which is held close to the object you are
viewing) and the ocular lens is a minus lens and closer to the eye.
Advantages
§ Widens the visual field, great for patients with peripheral vision loss
§ Lighter, shorter and cheaper
Disadvantages
§ Quality of visual image and detail is sometimes poor
Keplerian Telescopes
Keplerian Telescopes
use two convex (plus) lenses. The objective lens is of a smaller diopter power than the
ocular lens. This produces a real image but it is inverted & requires a prism to reverse the
image.
Advantages
§ Larger visual field than Galilean
§ Better optical image quality than Galilean
Disadvantages
§ Longer, heavier & more expensive than Galilean
important LVA equations
F/4 = Magnification Power of the lens
(F: Dioptres)
e.g. 10/4 = 2.5x – a 10 dioptre lens has a magnification power of 2.5x
1/F = Focal Length of a lens (m)
(F: Dioptres)
e.g. 1/10 = 0.1 m – a 10 dioptre lens has a focal length of 10cm (the object has to be held 10cm away from the lens to be perfectly in focus)
Current ‘N’ reading ability/Desired ‘N’ reading ability =
magnification needed to achieve this
e.g. Patient currently reads N10 with reading rx, but wants to read N5:
10/5 = 2
Therefore we need to supply the patient with a 2x magnifier to achieve this
Calculating magnification with Acuity Reserve
Acuity Reserve is calculated at 2:1 for the patient to achieve fluent reading.
Example:
A patient currently sees N24. They would like to read N12 fluently.
On the basis of a 2:1 acuity reserve, this means the patient must be able to spot read N6.
(N12/2 = N6)
Therefore, you must tailor the ‘current reading ability’ magnification equation listed just
above to
N24/N6 = 4
(rather than N24/N12 as this will not allow for fluent reading)
Therefore the patient will need a 4x magnifier to fluently read N12, and spot read N6.
flat field bar LVA
ADV
Bright – light gathering
Useful for px’s with hand tremor
Clear image across entire lens (aberrations have minimal effect)
Combo of bar & spec mounted magnifier can increase mag while maintain long viewing distance
Normal reading posture possible
DIS
Large lenses – heavy
Mag typically low
Reading material must be on flat/firm surface
telescopes LVA
for distance magnification
o Wear SVD
o Add rx to eyepiece
o Or alter telescope length (myope = shorten, hyperope = lengthen)
ADV
Can be for DV or NV & either monoc or binoc
Increased WD
Variable focus
Can be spec mounted & hands free
DIS
Expensive
Poor cosmesis
Heavy training required
Magnification of body movement
Poor field of view, approx 7 degrees (Field of view is optimised by patching size of exit pupil to px’s pupil (or ensure exit pupil is > px’s pupil) )
generally with LVA what does increased mag mean
Decreased FoV
Decreased WD
Increased illumination needed
daily living aids for LV px’s
Liquid level indicators
Talking microwaves / kettles
Talking watches
Large no. telephones
Coloured stickers / buttons
what is a typoscope
o Matt black card with a window cut out the width of a line
o Useful if RHS of vision has been lost due to stroke – eye is scanning into nothing so typoscope is used as a guide
o Field loss of LHS is not as bad but person may find it hard to find the beginning of the next line
meaning of the markings on telescope eg 8x24
o E.g. 8 x 24
o The number before the x is the magnification e.g. 8x mag
o The number after the x represents the diameter of the objective lens in mm e.g. 24mm
o Dividing the objective diameter by the mag gives us the exit pupil diameter e.g. 24/8 = 3mm
o This gives an indication of how bright an image will be seen px the px, as light leaving the system is determined by the exit pupil
Ideally want the exit pupil to match the px’s pupil, but having the exit pupil > px’s pupil allows for some misalignment, but some loss of field
o Some telescopes offer a third marking e.g. 7, representing the field of view
walking canes
o Symbol cane
Lightweight, folding can
Indicates that the user is visually impaired
o White walking stick
As symbol cane but also aids support
o Long cane
Most common type of cane
Swung in front of the px in an arc, at the end of travel it touches the ground before swinging the opposite way
o Guide cane
Shorter and stronger than the long cane
Back up for those with residual vision
o Available from social services, but can be bought from various charities
o If a white cane has red stripes, this indicates that the px also has impaired hearing
electronic LVAs advantages and disadvantages
- Aberration free
- Max mag up to 70x higher (limit of 30x is common)
- Zoom controls allow variable magnification
-Foreground/background colour options, windowing etc - Contract, luminance, enhancing
- Contrast reversal (50% of VIP prefer white on black)
- Binocular viewing
- Normal viewing distance/posture
- Variable camera-to-task and eye-to-screen distances
- Reading duration > optics LVA
- May be more psychologically acceptable than optical aids
- Cost: expensive to buy and service/repair
- Size depending on type/model
- Image quality – depends on screen
- Depth of field is limited by the focal length of the camera and can cause problems with thick books (use glass sheet to flatten out)
what are electronic LVAs
EVES form a direct cable link between the camera imaging system and monitor viewing system. Whereas plus lens magnifiers are made up of simple plus lenses and can be in the form of hand, spec-mounted, stand or flat field magnifiers. Eves are not available on the NHS, whereas plus lenses magnifiers are, but people tend to buy privately.
what is CCTV LVA
(closed circuit television)
- Stand mounted
- Still one of the most commonly used designs
- Each component fixed and mounted vertically “in-line”
- Working space fixed or limited
- For distance need second camera to be added
- Reading material needs to be flat – depth of focus
advantages of CCTV LVA and disadvantages
- Advantages
o Good of physical handicap
o Good for extensive VF defects, SES - Disadvantages
o Expensive, bulky, servicing and repair
o Practice required
o Control positions
what other electronic magnifiers are there
- hand held/ portable
- head mounted - DV and NV mag, high cost
- spec, hands free, widest FoV, binocular
