Low Vision Notes

Question 1

Definition of low vision

Answer 1

Any chronic visual condition not correctable by glasses, CL or medical intervention that impairs everyday function.

Question 2

What are the 3 categories of sight?

Answer 2

Normal vision, low vision and blindness

Question 3

What are the uses of LVA?

Answer 3

To maintain independence and make best use of remaining vision

Question 4

Types of LVA (optical)

Answer 4

Magnifiers and telescopes

Question 5

Types of LVA (NON-OPTICAL)

Answer 5

-Electronic vision enhancement software
-Apps and software
-lighting
-Tints
-large print
-talking books
-environmental design features
-sensory substitution (braille, echolocation, white canes)
-guide dogs

Question 6

Who are LVA assessment (optical) carries out by?

Answer 6

Optometrists and dispensing opticians within the HES
In private practices for HES and health boards (local schemes)
Private LVA Assessments

Question 7

Who are LVA assessments (non-optical) carried out by?

Answer 7

Social services or charities

Question 8

Who is able to certify who is blind or partially sighted (severely sight impaired Vs sight impaired)?

Answer 8

Severely sight impaired (blind):
VA BELOW 3/60
VA BETWEEN 6/60 AND 3/60 (WITH CONSTRICTED FIELD OF VISION
VA BETTER THAN 6/60 (CONTRACTED FIELD OF VISION ESPECIALLY IF IN LOWER FIELD)

Partially sighted (sight impaired):
VA of 3/60 to 6/60
Upto 6/24 with moderate contraction of visual field, opacities in media or aphakia
6/18 or even better if there is gross field defect e.g. heminopia of glaucoma

Question 9

What are other definitions of visual impairment?

Answer 9

Functionally blind (CANT see to read/write with use of LVA and CANT move in unfamiliar surroundings without use of GUIDE DOG/CANE)

Functionally sighted (CAN read/write with use of LVA and CAN move in unfamiliar surroundings without Guide dog/Cane)

Functionally sighted with aided mobility ( CAN read/write with use of LVA but CANT move in unfamiliar surroundings without Guide Dog/Cane)

Functionally sighted without sighted literacy (CAN move around in unfamiliar surroundings without Guide Dog/Cane but CANT Read/Write even with use of LVA)

Question 10

Definitions of Disorder, Impairment, Disability and Handicap, and difference between them?

Answer 10

Disorder- Deviation from ‘normal’ of any bodily structure

Impairment- An interference with a bodily function (e.g. VA or VF’s)

Disability- Lack, loss or reduction of an individual’s ability to perform certain tasks

Handicap- an individual’s perceived or actual disadvantage with respect to the expectations of the society in which they live and limits choice or independence

A disorder may cause impairment and the treatment of the disorder aims to prevent impairment. Disorder & Impairment are judged from a medical viewpoint while disability & handicap are social concepts. The aim of proving a patient with an LVA is to overcome impairment & prevent it causing disability.
Determination of degree of disability or handicap must take into account the requirements and expectations of the individual.

Disorder = ARMD
IMPAIRMENT = Reduced distance VA
DISABILITY= Loss of independence
Handicap = Inability to drive

Question 11

Scotland Registration Process & Forms

Answer 11

Certification: Patient is referred to ophthalmology department by GP, optometrist (via GP) or social worker (via GP) and CVI is completed by a consultant ophthalmologist.

CVI Form (Certificate of Vision Impairment)
􀁸 Certifies patient as blind, completed by consultant ophthalmologist
􀁸 Information to census office
􀁸 Access to help is not dependent on registration

Paediatric CVI Form
􀁸 This is to be completed in addition to the standard form and contains details about the disorder(s) resulting in visual impairment of the paediatric patient.

Question 12

Why should a patient get registered?

Answer 12

To determine funding & resource allocation it is important that accurate statistical information about the number of blind & PS patients is available nationally & for each local authority area.
Estimates suggest that up to 50% of patients who are eligible are not registered.

For the patient the main benefit of registration is that it allows access to services and benefits,
for example:
􀁸 Financial help (extra benefits and concessions e.g. income tax relief & VAT exemptions)
􀁸 50% off TV license for blind, not PS!
􀁸 Free BT-directory enquiries service
􀁸 Free GOS sight test (England)
􀁸 Transport (free in some areas, disabled car badge)
􀁸 RNIB- talking books & many other very useful services
􀁸 British wireless for the Blind Fund- radios

Question 13

Registration – Disadvantages and problems with the process

Answer 13

Loss of hope & self-esteem as many patients (and some professionals) see this as the ‘end of the road’, when nothing else can be done.
Problems
􏱃 Health care & other professionals may not tell patients about registration and it is often done as a last resort by ophthalmologist
􏱃 Poor communication between professionals involved- ophthalmologist, social workers, optometrists etc.
􏱃 Long waiting times
􏱃 Not enough social workers - may not be trained in dealing with LV patients
􏱃 Budget cuts & lack of funding

Question 14

What to consider before starting a LVA assessment?

Answer 14

Here are some points to consider before you start:
LVA assessments are time consuming – set aside sufficient time, especially for history (checklist/questionnaire)
􏱃 What does the patient want you to do (and is this possible)? 􏱄 Px expectations may be too high or very low
􏱄 Px may be distressed, disillusioned & tire easily
􏱄 Poor motivation
􏱃 The patient must agree with what you want them to do - they make the final choices!

Question 15

What to consider during LVA assessment?

Answer 15

The 􏱃 Adjust your speed to the patient (e.g. Elderly, children) and avoid unnecessary tests/procedures
􏱃 Keep talking to the patient. Don’t use gestures which they might not see!
􏱃 Get all their current/past spectacles and magnifiers if possible
􏱃 Encourage carers/family to be present unless patient objects
􏱃 Px may have other disabilities e.g be prepared to cope with hearing loss as well

Question 16

General observation of the patient from the moment you meet them or when you collect them from the waiting room can provide additional information. Here are some points to consider:

Answer 16

􏱃 Are they bothered by bright light?
􏱃 Any physical infirmities, which restrict range of activities they need to undertake and limit
their visual requirements, but also restrict the ability to handle LVAs.
􏱃 Do they look straight at you when talking, or use eccentric viewing?
􏱃 Can they navigate independently, or need to be guided? If guidance is required offer your
arm and use the correct sighted guide technique.

Question 17

How to correctly guide a VIP?

Answer 17

– VIP follows half a pace behind
– VIP takes guide’s arm slightly above elbow
– Change to holding wrist if space narrow (or guiding child)
– Crowds: in single file Steps
– keep up a running commentary
– say if they go up or down Doors
– VIP on same side as hinge
– Guide opens door and “hands it” to VIP Chairs
– approach from behind and put VIPs hand in centre of back-rest, or
– approach from in front, and put their hand on arm-rest, or seat
– VIP stands with back of knees touching edge of seat before sitting
– Guide should say if there are any obstructions round the chair

Question 18

History & Symptoms

Answer 18

The case history is a very important part of the LVA assessment. You must find out what the patient wants & what they require. This may not be the same thing!
Visual Status
You need to find out as much as you can about the patient’s lifestyle, their daily living requirements and specific hobbies and determine the impact of the visual impairment.
Some practitioners advocate the use of questionnaires (Figure 2) (Wolffsohn and Cochrane 2000).
Ask specific questions related to;
􏱃 Distance and Near Vision (ability to read newspaper, watch TV etc)
􏱃 Mobility
􏱃 Everyday tasks (e.g. kitchen)
􏱃 Hobbies or interests
􏱃 Different lighting conditions

Examples:
􏱃 How did they get there: public transport?
􏱅 Can they see the bus numbers, departure boards etc.? 􏱅 Can they cross the road safely?
􏱅 Does bright sunlight bother them?
􏱃 Can they see the TV?
􏱅 How close do they sit? Could they sit closer?
􏱃 Do they read?
􏱅 What? Books, newspapers or just bills etc?
􏱅 What size print can they see? Small print or headlines? How long can they read for? 􏱅 What sort of lighting?
􏱅 Where is the light positioned?
􏱃 Can they still write?
􏱃 Do they use a computer/tablet the internet?
􏱃 Do they manage about the house?
􏱅 cooker dials? food on a plate? labels on cans etc?
􏱃 Do they get home help, Social Service help?
􏱃 Do they have a pastime; knitting/sewing, gardening, music?

Often patients will tell you that they can’t see/read anything. What they actually mean is that they don’t enjoy reading, because it is difficult. It is important to find out what size print they would be able to manage (with effort), as this information is useful when calculating their magnification requirements!!!

Question 19

Ocular & General Health History

Answer 19

This is similar to a routine eye test and you usually go through this before examining the patient. However, often patients don’t remember any specific details about procedures/treatments they have received.
If the information that the patient provides seems inconsistent you may interrupt politely and come back to the question during or after the eye exam. In some cases the amount of useful information that you’ll be able to extract may be limited e.g. if the patient suffers from dementia.
Try and establish the following:
􏱃 Onset of impairment, duration and circumstances
􏱅 Stability of vision, difference between the eyes
􏱃 Ocular condition if known
􏱅 Cause, duration & onset (sudden onset patient may be too upset for assessment)
􏱅 Stability & prognosis (deteriorating, improving or stable)
􏱅 Current, past & future treatment
􏱃 General health and medication
􏱃 Physical infirmities (e.g. Arthritis or Parkinson’s - can’t hold hand magnifier.)
􏱃 Registration of vision impairment

Previous & Current Low Vision Aids
It is important to find out as much as you can about current and previously used LVAs. For example, if a patient used to be able to read newsprint with a particular magnifier and now they can only manage headlines it is likely that their eye condition has deteriorated. Ask questions regarding:
􏱃 Previous LVA assessments and previous LVAs used?
􏱃 Important: Have they previously tried LVAs that they didn’t find useful and Why?
􏱃 Current LVAs & spectacles used?
􏱅 Record VAs and details of currently used LVAs (e.g. power /magnification, how old?, condition etc. )

Occupation & Education
For patients of working age this is relevant as it will help you establish target VAs, required working distances and magnification needs.

Patients Motivation & Expectations
Patient motivation has a major effect on the outcome of an LVA assessment. If a patient is positive and willing to try new things and accepts the limitations of LVAs, they are much more likely to succeed using them. Establish the following:
􏱃 What does the patient hope you can do for them?
􏱃 Is their expectation realistic?
􏱃 If their expectation is unrealistic try to let them down gently, but do not promise things
you can’t deliver!!

Social Circumstances & Family
You may sometimes need to initiate a referral to social services/voluntary organisations:
􏱃 Live alone?
􏱃 Family & friends?
􏱃 Attitude of patient (angry, denial, confident, unconfident, depressed or accepting)
􏱃 Attitude of family (caring & supportive, over-helpful or uncaring)

Requirements & Priorities
It is important to prioritise. It is unlikely that you’ll be able to offer a solution for all of the patient’s visual problems.
Start and find out what task is most important to the patient?
Often, different LVAs will be required for different tasks and the Px may end up with several LVAs. Patients often have to accept that not all tasks can still be done (e.g. driving although some states in the USA still allow driving with a distance telescope!).
Sometimes a non-optical aid may be more helpful. Consider the patient’s individual circumstances, listen to the Px and ‘think outside the box’.

Psychological Aspects
As mentioned above MOTIVATION is very important! “What do you want me to do for you?” Patients must be ready and willing to accept help.
Beware of those who don’t want help because they feel that they benefit from their disability e.g. make the family feel guilty or like to have the grandchildren around to read letters to them etc.

Question 20

Psychological Adjustment to Vision Loss

Answer 20

It is generally accepted that the loss of ability (loss of sensory [e.g Vision], motor [ e.g. loss of a limb], intellectual or reproductive functioning) is comparable to a form of bereavement with a similar response sequence. The adaptation to the loss has been extensively described (Kubler-Ross 1975) and is a gradual process involving a series of 5 stages (loss model).
The psychological adjustment to loss involves perceptual, behavioural, cognitive and emotional adjustment.

Loss Model
The Loss Model is probably most appropriate to sudden visual loss. The five stages are:
1) Denial & shock
2) Grief
3) Anger
4) Depression & apathy
5) Acceptance

Shock
􏱃 Sudden loss, eg wet AMD or stroke
􏱃 Disbelief,
􏱃 Patient doesn’t appear to comprehend and doesn’t appear to be listening

Denial
􏱃 Not the same as disbelief
􏱃 Refuses to admit that they have a problem (good example is driving with reduced VA
against the advice of eye care professionals); Most of the public think that ‘blind’ =
complete darkness
􏱃 May refuse LVA’s (“I just need stronger glasses”)

Anger
􏱃 May feel that there is lack of or improper treatment
􏱃 Px may stop taking prescribed medication

Depression & apathy
􏱃 Hopeless situation, Going to get worse
􏱃 Nothing can be done and LVA assessment is a waste of time
􏱃 May need counselling or psychotherapy

Realistic acceptance
􏱃 Final stage
􏱃 Understands and accepts the condition
􏱃 Makes effective use of remaining VA
􏱃 Uses LVA’s, eccentric viewing, white stick etc.
􏱃 Happy to use aids in public

Question 21

Psychological Adjustment to Vision Loss-treatment

Answer 21

Treatment
􏱃 Prevent loss of competence- start rehabilitation as soon as possible
􏱃 Goal is to get them performing old tasks at a very early stage
􏱃 Simple techniques with positive feedback
􏱃 Tasks which show rapid progress
􏱃 Attribute failure to external influence and success to their own efforts

NB. Environmental factors can affect the process of adjustment to the disability e.g.
􏱃 Death of partner, relative or close friend
􏱃 Patient is carer for someone else
􏱃 Financial problems
􏱃 Reaction of relatives eg over helpful or don’t care

Question 22

1. Measure current distance best corrected VA (BVA) & Near BVA with aids & specs. It is often not useful to measure vision (abnormal relationship between vision and VA).

Answer 22

Measuring Visual Acuity
􏱃 use current correction if apparently correct
􏱅 beware of inappropriate balance lenses
􏱃 give the patient impression they are doing well – cooperation is key!
􏱅 if VA unknown start at a close distance (0.5 or 1m) and move back if necessary
􏱅 record test distance e.g. 1/36 ;
􏱅 DO NOT USE counting fingers (CF) – move chart closer instead
􏱅 VA notations if <0.5/60: HM, LProj, LP, NLP
􏱃 increase or decrease illumination if necessary
􏱅 e.g. rod monochromat-lights down, media opacities – may need additional
lighting 􏱃 recording:
􏱅 monocular & binocular VA as usual
􏱅 type of chart and test distance e.g. Snellen 1/36
􏱅 light level
􏱅 head turn/eccentric viewing etc. what

Question 23

Refract if needed

Answer 23

Objective – important because subjective often very difficult/variable.
Subjective
􏱃 Think about ‘Just Noticeable Difference’, DO USE LARGE STEPS!!!!!
􏱅 Sph: ± 0.5DS, ±1.00DS. ±3.00DS
􏱅 X-cyl: ± 0.50 or ±1.00
􏱅 DO USE bracketing techniques
􏱃 Direct the patient to single letters or lines and use comparisons e.g.: “Clearer with or without?”
􏱃 DO NOT ask open ended questions like: “How is it with this lens?” or “What can you read with this lens?”
􏱃 Reduce testing distance if required (adjust Rx for distance!)
􏱅 Px should be able to see about 4 lines of the test chart

Question 24

3. Establish distance magnification requirement

Answer 24

􏱃 Identify the visual task & estimate the VA that is required for the task (target VA [TVA])
􏱃 Calculate magnification requirement based on BVA and TVA
􏱃 Check if px achieves this with LVA
􏱃 Often more important for younger patients or children (ability to see board etc.)

Question 25

4. Near magnification requirement

Answer 25

􏱃 Identify the visual task & estimate TVA as above
􏱃 Measure BVA (usually at 25cm with the appropriate near add of +4.0 DS) & estimate the
magnification required to achieve TVA
􏱃 Assess central fields- if a defect is suspected (Amsler) before prescribing magnifiers; may
need to consider eccentric fixation
􏱃 Try predicted magnification – check VA with magnifier; modify magnification as required to
achieve target acuity
􏱃 start with simple magnifiers: high add, hand or stand magnifier
􏱃 Illumination
􏱃 Prescribe the LVA with clear instructions!!

Question 26

Other tests

Answer 26

􏱃 Establish binocularity (e.g. Cover test) and eye dominancy (many LVAs are monocular)
􏱃 Contrast sensitivity if indicated
􏱃 Fields (Amsler may be most useful in LVA assessment)
􏱅 Ophthalmoscopy/fundus photography, OCT, IOPs etc 􏱃 Spend your time wisely and do not do unnecessary tests

Question 27

Advice & follow up

Answer 27

􏱃 Important- patients often forget what the aid was intended for or how to use it
􏱃 Ideally review patient in 2-4 weeks
􏱃 may need to change LVAs

Question 28

Communication

Answer 28

􏱁 Speak slowly & clearly
o May have hearing loss - speak to best ear
􏱁 Be encouraging & positive
􏱁 Don’t rush the patient, but stay in control

Question 29

Snellen Chart
Advantages

Answer 29

􏱁 Well known, commonly used standard clinical measure of VA & vision
􏱂 Very sensitive to blur and uncorrected refractive error 􏱁 Good size (portability)
􏱂 Easy to move closer to patient 􏱁 Has letters ‘O’ suitable for x-cyl

Question 30

Snellen chart disadvantages

Answer 30

􏱁 Unequal numbers of letters on each line (crowding not constant)
􏱁 No relationship between line size & number of letters - from 1 to 8
􏱁 Poor control of ‘contour interaction’
􏱁 Unequal letter size progression- 1.2X increase from 6/5 to 6/6, 1.67X
increase from 6/36 to 6/60
􏱁 Designed to measure ‘normal’ acuity
􏱁 Scale intervals change at non-standard distances (crowding inconsistent)

Question 31

Using Snellen charts at a reduced viewing distance:

Answer 31

Example: A 6 metre letter letter viewed at a distance of 6 m (6/6), has a minimum angle of resolution (MAR) of 1arcmin (gap size or limb width; MAR =1as 6/6=1’).
A 24 metre letter is 4 times larger so MAR=4’ if viewed at 6m (24/6 = 4’)

If a Px with VA 6/24 views the chart at 3m they should be able to see the 12m letter (written as VA of 3/12) because this subtends the same visual angle 􏰧􏱃􏰨 as the 24m letter viewed at 6 m (MAR 12/3=4’).

Question 32

Bailey-Lovie (logMAR) chart (Bailey and Lovie 1976)
Advantages

Answer 32

􏱁 Size, letter and line spacing equivalent throughout chart
􏱂 Equal numbers of letters per row (5)
􏱁 Sensible progression of letter size (0.1 log or 1.25X)
􏱁 All letters have equal legibility
􏱁 Constant crowding for all VA levels
􏱁 Final score takes into account all letters that have been read successfully

Question 33

Bailey-Lovie (logMAR) chart (Bailey and Lovie 1976) Disadvantages

Answer 33

􏱁 LogMAR not used routinely as a clinical measure of VA
􏱁 Scoring and conversion not as easy as Snellen
􏱁 there’s no O letter for X-cyl
􏱁 A bit on the big side and may be hard to illuminate

Question 34

Using logMAR charts at a reduced viewing distance:

Answer 34

Rule of thumb:
Every time the viewing distance is halved add 0.3 to the logMAR -score.

Example (logMAR chart designed for 6 m)
Px views chart at 6 m
􏱁 Reads the 0.8 line + 2 letters on the line below
􏱁 logMAR VA is 0.8 - 0.04 = 0.76
Px views chart at 3 m
􏱁 Px now reads 0.5 line + 2 letters on the line below
􏱁 logMAR VA is 0.5 - 0.04 = 0.46 + correction factor of 0.3 for
moving from 6 to 3 metres 􏱄 0.46 + 0.3 = 0.76

Question 35

Near Vision Charts

Answer 35

The Faculty of Ophthalmologists Times New Roman near chart
N-Point Notation
􏱁 Standard reading chart widely used
􏱁 Based on printing standards
􏱁 1 point is 1/72”
􏱁 Top of ascending to bottom of descending limb of letter
􏱁 Times Roman type face
􏱁 Easy to understand and convert e.g N24 = twice size of N12
􏱁 Blocks of text

Bailey-Lovie Word-Reading chart
LogMAR chart
􏱁 2to6wordsonaline
􏱁 Unrelated words, no guessing
􏱁 Limited number of words on line - good test of
reading
􏱁 Difficult for children, those with poor English or poor cognition

Question 36

Prescribing Optical LVAs - Distance (Snellen):

Answer 36

E.g. telescopes

BVA … Threshold (Best corrected)
VA TA … target acuity
M… required magnification

M = BVA/TA

Example:
􏱂 Px can see 6/60, needs to see 6/12
􏱂 M = BVA / TA = 60/12 = 5
􏱂 5 x magnification required

Question 37

Prescribing Optical LVAs - Near:

Answer 37

Use N – point notation and test patient’s acuity at a distance of 25cm (+4.00 D Near Add if required)

M = BVA / TA

BVA … Threshold (Best corrected) VA
TA … target acuity
M… required magnification

Example=
Px can see N24 at 25 cm with the appropriate add of + 4.0 D?…needs to see N12
M = BVA / TA = 24 / 12 = 2
2 x magnification required

Question 38

Available LVAs:

Answer 38

􏱁 Magnifiers
􏱂 High add
􏱂 Spectacle
􏱂 Hand held
􏱂 Stand magnifier
􏱂 Electronic LVAs

Question 39

Choice of Magnifier

Answer 39

􏱁 Keep it simple!
􏱁 Start with low magnification if possible
􏱁 Illumination!
􏱁 Consider
􏱂 Task & age of patient
􏱂 Physical infirmities e.g. can the patient hold the magnifier/task steady?
􏱂 Cost

Question 40

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