Low Vision

Front 1

What is visual acuity?

Back 1

The ability to resolve or discriminate spatially organised detail.

Front 2

What is Visual Field?

Back 2

Visual Field = The extent of the area in space in which objects are visible to an eye in a given position.

Front 3

Define low vision.

Back 3

The WHO dines low vision as VAs > 6/18.

Front 4

STATE the criteria for SI.

Back 4

SI

- VA of 3/60 - 6/60 with a full visual field.

- VA of up to 6/24 with a moderate reduction of the visual field, or with blurry/cloudy central vision.

- VA of 6/18 or better with a gross field defect.

Front 5

STATE the criteria for SSI.

Back 5

SSI is classified into 3 groups.

Group 1 - VA < 3/60 (but not 1/18)

Group 2 - 3/60< VA <6/60 & a contracted field of vision.

Group 3 - VA > 6/60 & have a severely contracted field of vision. (especially inferior or bi-temporal hemianopia)

Front 6

DEFINE Blind (SSI).

Back 6

"So blind that they cannot perform any work for which eyesight is essential"

Front 7

Define Partially Sighted (SI)

Back 7

"Substantially and permanently handicapped by defective vision caused by congenital defect, illness or injury"

Front 8

What is the route for registration for SI or SSI?

Back 8

1. OO/DO refers Px to eye clinic.

2. Consultant OO tests Px for eligibility.

3. Px signs CVI form, this is sent to Office of national statistics, GP & Local Authority.

4. Local Services contact Px and ask if they want to be on its confidential registers.

5. Px is issued with a registration card.

6. Local services arrange a Social Care and Rehabilitation Assessment, to assess Px's needs and discuss entitlements.

Front 9

STATE 5 benefits of being registered as SI and SSI.

Back 9

- Free NHS Sight Test.

- Free/Reduced Bus Pass.

- Disabled persons Rail Card.

- Universal Credit.

- Pension Credit.

Front 10

STATE is the difference between Certification and Registration.

Back 10

Registration is to be registered under a local authority.

Certification is to be verified by a practitioner.

Front 11

What should be considered when thinking about visual function?

Back 11

- Binocularity

- Colour Perception

- Contrast Sensitivity (CS)

- Duplicity Theory

- Dark Adaption

- Field Loss or Scotoma

- Glare

- Visual Acuity

Hint 11

BCCDDFGV

Front 12

What is Contrast?

Back 12

The difference in colour and/or brightness of an object compared with the other objects in view.

Front 13

What is Contrast Sensitivity Function (CSF)?

Back 13

Contrast Sensitivity Function is an important measure of a person's ability to detect lower contrast stimuli.

This is a good measure of how a person's visual function will operate in real-world conditions.

Front 14

How do you calculate contrast?

Back 14

Front 15

How can CSF be measured?

Back 15

Gratings

- These are vertical stripes of decreasing shades of black to grey.

- The width between the Gratings can be changed to measure CS.

- This can be used to plot a graph of the patients spatial frequency.

Front 16

List 5 conditions that can result in changes in CS.

Back 16

- Cataract and Strabismic Amblyopia.

- Glaucoma.

- Anisometropic Strabismus.

- Defocus (ametropic) Blur.

- Diffusive Blur / Disability Glare.

- Retinal Atrophy / Defects.

Front 17

What is the major way to improve contrast?

Back 17

By improving illumination.

Front 18

What charts can be used to measure CS?

Back 18

- Pelli-Robson Chart

- Bailey-Lovie Chart

- Harsent NV Contrast Charts

- VISTECH Charts

- Electronic Charts

Front 19

Why do we measure CS?

Back 19

- It allows is to gauge visual performance under real-world conditions (Measure Visual Funtion).

- Allows is to predict the likely success of LVAs.

- Consider whether contrast advice and support are necessary.

- Calculate contrast reserve, and feeds into our prescribing strategies.

Front 20

List 5 features of the Pelli-Robson Chart.

Back 20

- Large low-portability chart.

- Must not get damaged / dirty/ marked.

- All letter are the same size (subtend 2.8° at 1m).

- 8 rows comprising of 2 triplets of letters.

- Each triplet of letters has the same contrast.

- Contrast reduces in a logarithmic progression.

- Contrast reduces across and down the chart by 0.15 log units

- Contrast ranges from 89% to 0.5%.

Front 21

How do you use a Pelli-Robson Chart?

Back 21

- Px is tested monocularly and the binocularly.

- Should take no more than 8mins.

- For use at 1m.

- Centre of Chart should be approx. eye level with Px.

- Chart should be illuminated as uniformly as possible.

- Avoid Glare or reflections on the surface of the chart.

- Illumination can be varied from 60-120cd/m².

- Px should wear +1.00DS addition if AoA is not sufficient.

- Px may require support and encouragement.

- Px should guess even when they believe the letters are invisible.

Front 22

What is the Photopigment, Vision, and Location of the Rods?

Back 22

Photopigment = Rhodopsin.

Vision = Scotpic, Low Acuity, Achromatic.

Location = Highest density away from macula.

Front 23

What is the Photopigment, Vision, and Location of the Cones?

Back 23

Photopigment = Red, Blue Green.

Vision = Photopic, High Acuity, Chromatic.

Location = Central Retina (fovea most dense)

Front 24

What is Scotoma?

Back 24

Scotoma = An area of reduced / no visual acuity surrounded by an area of relatively normal vision.

Front 25

Describe the following terms:

- Absolute Scotoma.

- Relative Scotoma.

- Negative Scotoma.

- Positive Scotoma.

- Hemianopia.

Back 25

- Absolute Scotoma is a defect that is present during all stimulus.

- Relative Scotoma is a defect that presents when stimulus is weaker.

- Negative Scotoma is a scotoma that is not generally perceived by a patient (blind spot).

- Positive Scotoma is a scotoma which is perceived by the patient (black spot in vision)

- Hemianopia is a loss of one half of your visual field.

Front 26

Describe the Amsler Chart design.

Back 26

- Grid of lines making squares.

- Central fixation spot.

- Designed to measure central 10° of visual field.

- Some have diagonal lines to aid fixation.

Front 27

How do you use an Amsler Chart?

Back 27

- Well lit room / daylight.

- Held at 30cm.

- Wear NV correction.

- Each eye occluded in turn.

- Px should stare at central fixation dot.

- Px should familiarise themselves with what their Amsler Chart looks like.

- Px should report any lines that are distorted or missing.

- Ideally use everyday.

- Ensure Chart is flat when used.

Front 28

What else can an Amsler Chart be used for?

Back 28

Rehabilitation

- Can be used to establish the preferred retinal location (PRL)

- Used in eccentric viewing training.

- Teaches Px to use the least damaged part of their visual field.

- Patients are taught to look away from the clearest part of the chart.

Front 29

What actions do you take when a patient reports changes in their Amsler Chart?

Back 29

- Refer immediately (acute referral).

Front 30

What is the general rule for testing with reduced acuities?

Back 30

<6/60 = 1-3m

6/24 - 6/60 = 3-4m

>6/24 = 6m

Front 31

State 5 disadvantages of the Snellen Chart in LV.

Back 31

- Too few letters at lower acuities.

- Non-logarithmic design.

- No contact ratio between size of letters.

- Non consistent spacing (crowding).

- Inconsistent letter legibility.

- Measures high contrast acuities only.

- Does not consider real-life environments.

- Designed for use at 6m.

- Over-etimates acuities if used at a closer WD.

- Does not allow estimates of magnification requirements.

Front 32

State 5 advantages of Bailey-Lovie Chart in LV.

Back 32

- Logarithmic in design.

- Constant ratio of letter size.

- Line and letter spacing equivalent throughout.

- Can be used at any appropriate WD.

- Allows more accurate prediction of mag requirements.

- Each line has 5 letters for improved accuracy / reliability.

- This also removes memorisation.

- Each letter has a score which also improves accuracy.

Front 33

What are is 1.0logMAR and 0.0logMAR in snellen acuity?

Back 33

1.0logMAR = 6/60

0.0logMAR = 6/6

Front 34

Why do we magnify? PPQ

Back 34

Stock answer

- A patient with AMD has central scotoma & CS loss.

- Any images falling on this area will be poorly (or not) perceived by the visual cortex.

- Magnification will create a large image on the retina/macula.

- Pushing some of the image onto the undamaged/less damaged areas of the retina.

- Enabling it to be perceived by the Px.

Front 35

How can you calculate Magnification?

Back 35

Magnification = NEW RIS / OLD RIS

Front 36

RSM

Back 36

Relative Size Magnification (making the object bigger)

RSM =acuity achieved / acuity required.

- This is the magnification achieved by increasing the size of the object.

(e.g. large print books, larger TV, larger font size on VDU/tablet/phone)

Front 37

What are the practical advantages and limitations of RSM?

Back 37

Front 38

RDM

Back 38

Relative Distance Magnification.

RDM = Original object dist / new object dist

This is the mag achieved by reducing the object distance (sit closer to TV, hold print closer)

Front 39

What are the practical advantages and limitations of RDM?

Back 39

Front 40

What is the formula for Angular Magnification (AM)?

Back 40

AM = qL / 1-dL'

(q & d are in meters)

Front 41

How do you calculate Mnom and Mmax for both thin and thick lenses?

Back 41

Thin lenses

Mnom = F / 4

Thick lenses

Mnom = Fe / 4

Fe = F1 + F2 - t/nF1F2

For Mmax just +1

Front 42

What is Nominal Magnification?

Back 42

Nominal Magnification is a special case of Angular Mag.

It can only be achieved when:

- Object is at 1st principal focus.

- Image is formed at infinity.

- Was prev working at RSD (-25cm)

Front 43

What is Maximum Magnification?

Back 43

Maximum Magnification is a special case of Angular Mag.

It can only be achieved when:

- Vertex = 0

- Image is formed at RSD (-25cm)

- Was prev working at RSD (-25cm)

Front 44

STATE 5 features of an appropriate task lamp for use by a Px with AMD.

Back 44

- Adjustable WD

- Adjustable Brightness.

- Adjustable Colour Temp.

- Adjustable direction of light (to reduce glare)

- Low Heat (LEDs)

- Opaque back (to reduce glare)

- Simple to use.

- Cheap to buy/run.

- Portable

Front 45

STATE 5 reasons for reduced near VAs.

Back 45

- Conditions affecting Central Scotoma.

- AMD, Diabetic Retinopathy, Retinitis Pigmentosa, Chronic Open Angle Glaucoma.

- Poor Contrast Sensitivity

- Poor Lighting.

- Glare

Front 46

How do you calculate estimated Mag for Distance and Near?

Back 46

Distance (we aim for 6/12-6/10)

Near will be stated in the Question

acuity achieved / acuity required

Front 47

LIST 5 Distance telescopes.

Back 47

- Spotter (handheld monocular)

- Adjustable handheld monocular

- Binoculars

- BiOptic

- Spec mounted Telescopes

Front 48

Describe the Objective Lens (Fo) in a Distance Telescope.

Back 48

- The lens Nearer the object

- The Entrance pupil for the telescope.

- The Diameter controls the FOV.

Front 49

Describe the Eyepiece Lens (FE) in a Distance Telescope.

Back 49

- The lens Nearer the Patient.

- It is ALWAYS THE HIGHER POWERED LENS.

- Sometimes a series of lenses to help control aberrations.

- It's position controls FOV.

- NOT the exit pupil.

Front 50

STATE 5 tasks a distance telescope can be used for?

Back 50

- Seeing bus times.

- Seeing departure boards.

- Supermarket isle signs.

- Cinema.

- Football.

- Lectures.

- Museums.

Front 51

Define "Afocal" in regards to a telescope.

Back 51

Parallel light enters and parallel light leaves.

Front 52

How do you calculate magnification in telescopes?

Back 52

M = -FE / Fo

Front 53

STATE 5 facts about "Atronomical Telescopes"

Back 53

- Two convex lenses.

- Inverted image.

- Exit pupil is real.

- High Mag.

- Big FOV.

Front 54

How do you calculate Tube length in an astronomical telescope?

Back 54

d = fo' + fe

Front 55

STATE the benefits of astronomical telescopes.

Back 55

- The exit pupil is real and outside the device (aerial).

- This gives us a wider FOV.

- Larger Mag Range.

- Better image quality.

Front 56

STATE the limitations of astronomical telescopes.

Back 56

- Inverted image

- Long & Heavy (conspicuous)

Front 57

What makes a "Terrestrial Telescope" unique?

Back 57

An astronomical telescope can be modified to create an upright image using an erecting lens.

(Porro Prism or Roof "Pechan-Schmit" Prism)

(This makes the device heavier, longer, more expensive)

Front 58

STATE 4 facts about "Galilean Telescopes"

Back 58

- Objective Lens (Fo) is convex.

- Eyepiece (FE) is concave.

- Upright image.

- Exit pupil is virtual (inside device)

Front 59

STATE the conditions for a Galilean Telescope to be "Afocal".

Back 59

The 2nd principal focus of the objective lens (fo') must coincide with the 1st principal focus of the eyepiece (fe).

fo' = d + fe

Front 60

STATE 4 benefits of Galilean Telescopes.

Back 60

- Cheap.

- Compact (conspicuous).

- Therefore lighter & more portable.

- Upright Image.

Front 61

STATE 4 limitations of Galilean Telescopes.

Back 61

- Low Mag.

- Exit pupil is virtual.

- Therefore smaller FOV.

- Lower image quality.

Front 62

STATE what happens when your reverse a Galilean Telescope?

Back 62

- It becomes a field expander.

- This minifies the image on the macula.

- This increases FOV.

- This Reduces VA.

Front 63

How can a distance telescope be modified to view a near object?

Back 63

- Increase tube length.

(becomes more positive)

- Add a positive lens cap

(neutralise the '-ve' vergence)

Front 64

List as many NEAR LVAs.

Back 64

- Hand mag - Stand Mag - Bar Mag - Pocket Mag - Prismatic Readers - Spectacle mounted telescopes - Sheet Mag - Chest Magnifier - Hyperoculars

Front 65

List as many DISTANCE LVAs.

Back 65

- Spectacle mounted telescopes - Monocular handheld telescope - Maxx TV Specs - Tinted Overspecs

Front 66

List as many Special Optical Appliances.

Back 66

- Clip-on magnifier - Fresnel Prism - Monocle - Halfeye specs - Reading Specs - Recumbent Specs - Surgeon's specs - Safety Specs - Trigeminal Specs - Ptosis prop - Flip up specs - Make-up Specs - Reversable Specs - Paediatric specs

Front 67

List as many Sports Appliances.

Back 67

- Snooker Specs - Sports Goggles - Shooting Specs - Cycling Specs - Swimming goggles - Aquavis - Diving mask - Skiing goggles

Front 68

Who is involved within a multi-disciplinary team?

Back 68

Mobility Officer (cane training) - ECLO (Eye Clinic Liaison Officer) - LV Specialists - DOs & OOs - GP - Audiologists - Local/National Charities - Physical Therapists - Ophthalmology - Dept. Work & Pensions.

Front 69

STATE 3 non-optical aids.

Back 69

- Bump-Ons

- Dycem Mat

- Liquid level indicator

Front 70

Define impairments.

Back 70

Problems in body function and structure such as significant deviation or loss.

Front 71

Define Functioning.

Back 71

An umbrella term for body function, structure, activities, & participation.

Front 72

Define Activity Limitations.

Back 72

Difficulties a person may have in executing activities.

Front 73

Define Participant Restrictions.

Back 73

Problems an individual may experience in involvement in life situations.

Front 74

Define Environmental Factors.

Back 74

The physical, social, and attitudinal environment in which people live and conduct their lives.

Front 75

Define Performance Qualifier.

Back 75

How a patient performs in their current environemt.

Front 76

Define Capacity Qualifier.

Back 76

How a patient performs a task or action in the best possible fashion.

(i.e standardised environment)

Front 77

Angular Mag Formula

Back 77