Low Vision

Question 1

possible referral pathways and what info needs to be given

Answer 1

• 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

Question 2

examples of emergency same day referrals

Answer 2

➢ 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

Question 3

Urgent Referral (1 week) examples

Answer 3

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

Question 4

Disability and Equality Act (2010):

Answer 4

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

Question 5

Different Types of Disabilities

Answer 5

Physical – Amputation, Motor Neuron Disease, Advanced MS
* Sensory – Blind or Deaf
* Intellectual – Dyslexic, Dementia, Down Syndrome
* Emotional – Anxiety or Depression
* Developmental – Autism

Question 6

what is RVI – Registration for Visual Impairment

Answer 6

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.

Question 7

what is the LVL - low vision leaflet

Answer 7

 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.

Question 8

what is VINCYP - Visual impairment network for children and young people

Answer 8

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)

Question 9

Adaptation of routine for Px with visual impairment

Answer 9

 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

Question 10

how to calculate which magnification to to use

Answer 10

use 4 x table
if N16 then started with 4x mag
trial and error

Question 11

pelli robson chart

Answer 11

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

Question 12

log MAR chart

Answer 12

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

Question 13

Sight impaired benefits of registering

Answer 13

Disabled person’s railcard
Free telephone directory enquiries
Protection under Equality Act
Universal credit, pension cried, tax credits

Question 14

Severely sight impaired benefits of registering

Answer 14

As with SI, but also…
Blue badge
50% off TV license
Free postal service
Council tax exemptions (up to £2,290)

Question 15

Criteria for registration as SEVERELY SIGHT IMPAIRED (SSI)

Answer 15

 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

Question 16

Criteria for registration as SIGHT IMPAIRED (SI)

Answer 16

 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)

Question 17

CVI - certificate of visual impairment

Answer 17

 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

Question 18

LVAs - assistive tech like apps

Answer 18

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

Question 19

non optical aids for LVAs

Answer 19

• 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

Question 20

difference between registration and certification Low vision

Answer 20

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.

Question 21

other definitions
- functionally blind
- functionally sighted
-functionally sighted with aided mobility
- functionally sighted without sighted literacy

Answer 21

 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)

Question 22

ECLO = Eye Clinic Liaison Officer

Answer 22

• 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.

Question 23

if px could not read chart and had to be brought closer, how would VA be measured?

Answer 23

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.

Question 24

lighting needed by low vision px

Answer 24

 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

Question 25

What non optical measures can improve lighting glare etc

Answer 25

 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

Question 26

discomfort glare

Answer 26

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

Question 27

disability glare

Answer 27

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

Question 28

what type of filters to px’s with AMD prefer

Answer 28

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

Question 29

glare adverse effects

Answer 29

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

Question 30

why is contrast sensitivity measured

Answer 30

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

Question 31

common causes of VI

Answer 31

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

Question 32

hand held magnifers, instructions, adv and dis

Answer 32

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

Question 33

stand magnifier

Answer 33

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

Question 34

spectacle mounted telescope LVA

Answer 34

 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)

Question 35

Galilean telescopes

Answer 35

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

Question 36

Keplerian Telescopes

Answer 36

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

Question 37

important LVA equations

Answer 37

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

Question 38

Calculating magnification with Acuity Reserve

Answer 38

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.

Question 39

flat field bar LVA

Answer 39

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

Question 40

telescopes LVA

Answer 40

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) )

Question 41

generally with LVA what does increased mag mean

Answer 41

 Decreased FoV
 Decreased WD
 Increased illumination needed

Question 42

daily living aids for LV px’s

Answer 42

 Liquid level indicators
 Talking microwaves / kettles
 Talking watches
 Large no. telephones
 Coloured stickers / buttons

Question 43

what is a typoscope

Answer 43

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

Question 44

meaning of the markings on telescope eg 8x24

Answer 44

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

Question 45

walking canes

Answer 45

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

Question 46

electronic LVAs advantages and disadvantages

Answer 46

• 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)

Question 47

what are electronic LVAs

Answer 47

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.

Question 48

what is CCTV LVA
(closed circuit television)

Answer 48

• 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

Question 49

advantages of CCTV LVA and disadvantages

Answer 49

• 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

Question 50

what other electronic magnifiers are there

Answer 50

• hand held/ portable
• head mounted - DV and NV mag, high cost
• spec, hands free, widest FoV, binocular