What is Low Vision

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What is Low Vision?

• Mary Bairstow
• LV Services Implementation Officer

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About the presentation

• Low Vision - what is it?
• Medical models and the role of the clinician
• Eye Examination and Refraction

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Low Vision Services Implementation

• Late 1990s
• More and better services
• Low Vision Report
• Sets standards and suggests LVSCs as a means to
  change

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A person with low vision

• ..is a person who has an impairment of visual
  function (not remediated by conventional specs,
  contact lenses or medical treatment) and which
  causes restriction in that persons life
• Paraphrased version of Definition 3.1 from the LV
  Report

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Defining Low Vision

• A low vision service is a rehabilitative or
  habilitative process which provides a range of
  services to make use of eyesightto achieve
  maximum potential.
• This is not just a technical process
• Low Vision Report

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A joined up, integrated,multi-disciplinary
partnership

• It is not practical for any single professional
  group or agency to provide all the elements
  required to provide a comprehensive low vision
  service

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The person

• What if ?
• Specs or contact lenses ?
• What about a a cure ?
• What if they
• cant read or make a cup
• of tea or crochet or .

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Eye disease and its management

• 'To the epidemiologist falls the task of
  reconciling the clinician's model of disease
  process with the social scientist's interest in
  the disability it causes. The difficulty lies in
  getting the balance right'
• Cullinan 1997

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Conditions, diseases,etc...

• Albinism, Bests disease, coloboma,
• diabetic retinopathy, Ehlers-Danlos syndrome,
• Fuchsdystrophy, glaucoma,
• Hermansky-Pudlak, ischaemic optic neuropathy,
• juvenile cataract, keratoconus,
• Lebers optic neuropathy..

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Eye Care Pathways

• Optometry - screening
• GP - whole person, not gate-keeping
• Hospital Eye Services
• Discharge to optometry
• Social Care

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Low Vision Model - a Maze
Optometry
Self referral
GP

Medical/ Surgical (3)
Eye Clinic - Consultant
Rehabilitation and other services
LV /or Rehab?
Low Vision Service Assessment Equipment Supply
Review LV
Social Care Assessment
Community Care Assess-ment
Low Vision Training
Rehab Training
Key Primary Route
Secondary Route. end
of training/treatment. Blue indicates first point
of contact for patients. Red indicates
Rehabilitation based services?
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Hospital Eye Services

• Ophthalmologist
• Orthoptist
• Optometrist
• Technician
• Ophthalmic nurse

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Diagnosis and Management

• Investigate
• Diagnosis
• Treat
• Monitor

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Sort it !

• Ophthalmology - Cataract, Lumps and blockages
• Optometry - LV and Contact lenses
• Orthoptists - Double vision

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Watch it !

• Monitoring glaucoma, diabetic retinal health
• Special tests biometry (ultra-sound of eye),
  pachymetry (corneal thickness), tomography
  (mapping back of eye) , perimetry (peripheral
  vision)

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Community Optometry

• Eye Disease -Gatekeeping role
• Correction of refractive errors - glasses

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Language

• Specificity and Sensitivity
• Sensitive - How many found
• Specific -How many correctly found

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The optometrist -Is it ever 'routine'

• The 'routine' eye examination
• History and Symptoms
• Examining the eye
• Vision
• Refraction
• Eye movements and Co-ordination
• After the examination

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History and Symptoms

• Activity 1
• In pairs - One person optometrist
• - One person patient
• - What do you want to know?
• - Why?
• As a rehabilitation worker would you ask the
  same questions ?

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History and symptoms

• Reasons for visit and symptoms
• Some optometrists use questionnaires
• Eye detectives
• Symptoms - Any double vision?
• - Dry, itchy eyes
• - Flashes and floaters?
• History - medical (diabetes,blood
  pressure)
• - family
• - eye problems

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Examining the eye

• Inside and out (fundus and anterior eye)

A bio-microscope or slit-lamp enables a
magnified image of the front of the eye
Fluorescein -A green dye changes colour with
light shines
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Fundus (not fun dust )

• Inside the eye
• Record all normal features
• Macula, disc, periphery etc
• Check with and without magnification

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Other tests

• IOP Applannation (Touching)
• - air puff tonometer
• Narrow drainage angles gonioscopy
• Health checks
• Blood pressure

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What is visual acuity

• Vision is seeing
• Acuity is a measure of degree
• Visual acuity is a measure of the smallest detail
  a person can just see

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Limit of sight

• It is the gap we can just see
• Make the same sized angle at different distances

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The eye test chart- visual acuity

• The smallest detail able to see
• Helps estimate how much can be seen
• Does not explain everything
• Can be done with very small
• babies using stripes

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Testing small children

• Preferential looking
• Stripes as borders

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6/6 20/20

• Standard 6/6 20/20
• The letter I can just see at 60m (a big swimming
  pool) is the biggest letter on the chart at 6m

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LogMAR chart

• Better for LV and accuracy
• Snellen acuity is usually on a row basis
• Row being recorded if most of the letters read
• Confusion if record 6/12- or 6/12
• LogMAR - 0.1 each row
• Each letter scores 0.02
• Letters equally weighed
• Progressive size change

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Using Symbols
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Close work

• N charts - not consistent, not linear
• - different cards different
  sizes
• M charts - A 1M approx. the size of lower-case
  newspaper print. 2M is 2 times bigger than 1m
• Bailey-Lovie n charts - logarithmic base
• Need to measure working distance !

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Activity 2 -thats the limit

• In pairs
• Hold the reading card at twice your usual reading
  distance
• Measure the smallest print you can see
• Measure the print you are most comfortable
  reading
• Discuss how you feel being tested

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Them and Us

• Threshold v Sustained vision
• Repeatable v Realistic
• Comfortable v accurate

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Peoples impressions

• Lighting conditions unrealistic
• Like to sit closer
• Tests should be easier
• Our Better Vision 1999 - Ryan and McCloughan

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Testing times

• Its devastating when you find out that you
  cant even read the top line. And you come out
  and you find that youre drained and you feel a
  lump in your throat
• Our Better Vision 1999 - Ryan and McCloughan

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Size reserves

• Acuity reserves
• Fluent reading
• 160 words per minute
• 31 acuity reserve
• Spot or survival reading
• 40 words per minute
• 11 acuity reserve

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Refraction

• Getting the right prescription (Rx)
• Retinoscopy
• Hand held device shines light at the back of the
  eye
• Children and people with learning disabilities
  spectacles

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Cross-Cyl
Acknowledge- design for vision Larry Bergman -
colorxrays.com
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Refraction

• Trial Frames
• Phoropter head looks more high tech hold
  lenses in front of eyes
• Subjective refraction cross-cyl
• - fan and
  block
• - duo-chrome
• Bracketing techniques allow accuracy

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Refractive error

• Cornea power and eye length must correspond
• Emmetropia perfect focus clear sight without
  specs.
• Focus for near objects provided by ciliary
  muscles accommodation

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Myopia

• Eye too long, cornea too curved
• Corrected by -ive lenses
• Progressive myopia has pathological changes
• Myopes gt risk glaucoma, retinal detachment

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Myopia
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Hyperopia

• Cornea too weak, eye too short
• If low to moderate can be overcome by focus
  (children have accommodation)
• Small eyes and eye structure more at risk acute
  glaucoma

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Hyperopia
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Astigmatism

• Occurs to some degree in 100 population
• No eye is a perfect sphere
• One axis is steeper
• Trans-Atlantic misunderstandings Rugby and
  football or football and baseball

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Astigmatism
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Presbyopia

• Lens thickens and loses flexibility with age
• Happens to all over 50s
• Same for children without lenses (cataracts)
• Dual correction of sight requires bifocals,
  varifocals
• Advances in multi-focal intra-ocular lenses

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Presbyopia
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Near Focus

• Checked in young people
• Presbyopia means ive lenses focus at close
  working distance

• Benjamin Franklin

• inventor of bifocals

(acknowledgement to College of Optometrists)
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Volunteers please

• Demonstrating - strong positive lenses
• Mimicking long sight
• Image difference and double vision

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Revision/Reminder

• Myopia image falls in front of retina
  negative lenses (concave)
• Hyperopia image would be created behind retina
  (convex)
• Presbyopia lack of focusing power for near
  tasks (accommodation)
• Astigmatism Shape of eye requires two axis's of
  focus

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New words?

• Aphakia

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Eye Movements and Co-ordination

• Simple cover test
• Maddox Rod
• Maddox Wing
• OXO tests

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Maddox Rod

• Using a Maddox Rod a red line appears across the
  room

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2 glaring omissions

• Contrast
• Peripheral vision
• For further discussion?

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After lunch - activity 3

• Look at the ive and -ive lenses
• Can you work out which would correct for
  presbyopia
• With the positive lenses - see if you can find
  the focus points of the lenses.
• Is there anything different about a lens that
  corrects astigmatism?

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Optometric Summing up

• Advice to Patient
• Spectacles types, materials
• Referral

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Another summing up

• Low Vision definition
• The role of clinicians
• Basics of optometric care

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Contact details

• Practical bit after lunch
• M.bairstow_at_vision2020.org.uk

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Focusing lenses

• 1D Focusing power of lens of 1m
• Reciprocal of Focal Length in cms
• 4D 1/focal length 100/25
• Lens required to focus at 25 cm length is 4D
• So what lens at 10cms ?

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