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Binocular vision, visual impairment and paediatrics > Low Vision Assessment > Flashcards

Low Vision Assessment Flashcards

1
Q

What to observe in a low vision assessment

A
  • A low vision assessment starts even before the patient enters the examining room
  • Postural abnormalities – head tilt
  • Mobility
  • Appearance
  • Have they come on their own or with somebody
  • Do they have a guide dog
  • Are they using a guide or a long cane
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2
Q

What is important in history taking in a low vision assessment

A

Understand what sort of difficulties px is having
- This gives an idea about how we can help overcome those difficulties

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3
Q

What should history taking in low vision assessment include

A
  • Duration of condition and onset
    • ‘When did you start having difficulties managing with your glasses’
  • Stability of condition and difference between the eyes
    • Has it been changing or has it been stable for many years
  • Patient’s knowledge of the condition and prognosis
    • A better understanding means we can manage the condition better and can help px better
  • Ongoing hospital monitoring and or treatment
    • e.g. if px has cataract and doing cataract surgery in next month , no point changing their glasses but if doing surgery 6 months down the line, then will change their glasses
  • Whats causing vision loss – what sort of problems px has
  • Whats causing problem
  • How long have they had this eye disease – when did it start
  • Registration status
    • Is px registered as being sight impaired or severely sight impaired
    • Are they not registered but eligible for registration?
  • Education and or employment
    • I.E. school/child/help – any difficulties – type of difficulties – access to access to work scheme
  • Present aids and spectacles
    • E.G. hand held magnifiers and technology
    • Do they have mobile electronic device/ apps
    • If they don’t have aids, why not
    • If they have any aids, any problems with it
  • Do they have any spectacles – distance, near – SV or varis
  • General health and medications
  • Reason for making the appointment
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4
Q

What should history taking in low vision assessment include

A
  • Duration of condition and onset
    • ‘When did you start having difficulties managing with your glasses’
  • Stability of condition and difference between the eyes
    • Has it been changing or has it been stable for many years
  • Patient’s knowledge of the condition and prognosis
    • A better understanding means we can manage the condition better and can help px better
  • Ongoing hospital monitoring and or treatment
    • e.g. if px has cataract and doing cataract surgery in next month , no point changing their glasses but if doing surgery 6 months down the line, then will change their glasses
  • Whats causing vision loss – what sort of problems px has
  • Whats causing problem
  • How long have they had this eye disease – when did it start
  • Registration status
    • Is px registered as being sight impaired or severely sight impaired
    • Are they not registered but eligible for registration?
  • Education and or employment
    • I.E. school/child/help – any difficulties – type of difficulties – access to access to work scheme
  • Present aids and spectacles
    • E.G. hand held magnifiers and technology
    • Do they have mobile electronic device/ apps
    • If they don’t have aids, why not
    • If they have any aids, any problems with it
  • Do they have any spectacles – distance, near – SV or varis
  • General health and medications
  • Reason for making the appointmentDistance vision -history and symptoms - low vision assessment:
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5
Q

Distance vision -history and symptoms - low vision assessment:

A
  • Difficulty seeing faces, buildings, cars, street signs, road signals, bus numbers and steps.
  • Vision fluctuates or not
  • Eccentric viewing status
    • Especially if they have central vision loss E.G. AMD or stardust viewing -
  • Problems with glare
    • Wears tinted glasses?
  • Vision better outdoors OR indoors
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6
Q

WHAT IS ECCENTRIC VIEWING:

A
  • A technique used by people with central vision loss.
  • Where the person looks slightly away from the subject in order to view it peripherally with another area of the visual field
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7
Q

Mobility - low vision assessment:

A

Does patient walk alone or accompanied in new/familiar environments

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8
Q

At home - low vision assessment:

A
  • If patient lives alone or with family – if alone, might need more help
  • Difficulty getting around house
  • Difficulty watching TV
  • Difficulty with colours
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9
Q

Reading, Close Work and Hobbies - low vision assessment:

A
  • Difficulty seeing books, newspaper, headlines, large print, own writing
  • Vision better in dim or bright light
  • Difficulty with hobbies such as sewing, bingo etc
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10
Q

Examples of px priorities in low vision assessment:

A
  • Wants to read newspapers
  • Correspondence
  • See train timings at railway station
  • Make a note of them and summarise findings to px
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11
Q

Measuring VA - low vision assessment:

A
  • Record Visual Acuity monocularly and binocularly
  • With and without low vision aid e.g if wear glasses, record vision with habitual correction
  • Best to start testing VA at close distances and then modify cause most people at clinic wont be able to see 6/6 on chart at 6m
  • Never resort to ‘counting fingers’ – cant bring chart to 3m or 1m
  • VA should be recorded precisely E.g. 3/60 not <6/60
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12
Q

Measuring near VA low vision:

A
  • Record the distance at which near vision measurement was made.
  • Measure reading speed if possible
  • Make sure that field of illumination is uniform and glare free – overhead lighting
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13
Q

Example of recording VA:

A
  • Distance VA (unaided)
    • RE: 3/60 LE: 2/60 BE: 3/60
  • Distance VA (with Eschenbach telescope, 6X) Used with RE
    • RE: 6/9
  • Near VA (reading glasses)/MNREAD charts
    • RE:N36 LE:N36 BE N36@ 40 cm
  • Near VA (Eschenbach HM, 6X)
    • N6 at 12 cm
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14
Q

What vision aid can be used for distance VA:

A
  • Glasses
  • Magnifier
  • Telescope
    = state which type it is
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15
Q

What should be noted if magnifier is used:

A
  • What the mag is
  • Which is it used in front of
  • What type of magnifier it is
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16
Q

What should be noted for near VA:

A
  • What chart was used
  • Working distance
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17
Q

Determining refractive correction - low vision assessment:

A
  • Perform Retinoscopy
  • In difficult cases use old glasses as a guide but be careful
  • Use a trial frame and full aperture lenses
  • Determine if they need an update for their glasses at distance or near
  • Use +/- 0.50DC JCC to refine cylinder
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18
Q

How to do ret on low vision assessment px:

A
  • If dull reflex = move closer = take working distance into account
  • If poor VA E.G. 3/60 = 0.05 refine correction using large steps. E.g. +/- 2D
  • But if better than 6/12 or 6/18, can refine in smaller steps such as +-0.50
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19
Q

What do you do if person has a high refractive error:

A
  • Might want to do refraction over the glasses
  • So add the lenses to the existing spectacles and work out what the new rx will be
  • = Use Halberg clips for high refractive errors
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20
Q

What to do if you get a ret value with poor VA E.G. 3/60 - what is the refraction routine:

A
  • Start off with + / - 8.00D
  • If px prefers -8.00, put it in trial frame
  • Then bracket again this time adding +/- 3.50D over the -8.00
  • If the px prefers a +3.50
  • There is a -8.00 in trial frame and with the +3.50 in, that leaves you with a -5.50
  • So leave that in trial frame
  • And then bracket with a +/- 1.25D
  • And if px accepts +1.25, that leaves you with power of -3.75 so leave that -3.75 in
  • Then estimate cyl axis with cross cyl so you present the cyl at 90 and 180 degrees and then at 135 and 45
  • If px prefers 90 and 135, then put a cyl of for example at 150 as somewhere between 90 and 135
  • And estimate cyl power (begin with -1.50D at estimated axis)
  • Refine Sphere, then cyl axis and then cyl power
  • Fine tune sphere and cyl power
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21
Q

What to do after subjective refraction:

A
  • Check Binocular status
  • Find out if any addition is required
  • CT, EOM if required
22
Q

What to do if closer working distance:

A

Take away plus

23
Q

How to work out add - low vision assessment:

A
  • Start off with add appropriate for their age or according to their old glasses
  • Then keep increasing the addition until you get as close to N6 as possible
  • E.G if start off binocularly with addition of +2.00 and the px is only able to read N10
  • Then you put in a +2.50 and the px can see N8 , then a +3.00 and px can see N6
  • Every time you increase the add, you need to get the px to move the reading material closer to them
  • Cause if you increase add and keep the reading material in same position, they wont be able to see clearly
  • So when increasing add, modify working distance
  • DO NEAR ADD ON TOP OF DISTANCE CORRECTION
24
Q

What to use for near correction add:

A
  • +4.00D wd 25 cm
  • Best to use a word chart to what px can see at near
  • Cause magnification is linked to +4.00 D wd 25 cm, some might measure what px can see with 4D addition cause 4D addition is considered to be 1x magnification
  • Record what type of illumination was preferred
25
Q

Additional tests for low vision assessment:

A
  • Visual Field testing : area of distortion/defect
    • Amsler Grid
    • Goldman Perimeter
    • Nidek MP1
    • Confrontation
  • Contrast Sensitivity
26
Q

Why do gross confrontation visual field test:

A

If px has history of stroke and potentially has hemianopsia

27
Q

What do most low vision px’s need in assessment:

A

10-20% of low vision patients need only a GOOD REFRACTION and ADVICE ON LIGHTING

28
Q

What is required to appreciate subjective improvement:

A

An increase of at least two lines is required in VA to appreciate subjective improvement

29
Q

Do all px benefit form low vision aids:

A
  • Not all patient benefit with LVA.
  • May need sensory substitution or other strategies e.g audio devices or tactile devices
30
Q

When would you change rx in low vision assessment:

A

ONLY CHANGE RX IF PX INSISTS OR IF IT IMPROVES THEIR VA BY AT LEAST TWO LINES OR MORE

31
Q

How to prescribe magnification:

A
  • Determine whether monocular or binocular correction would be preferable for the aid
  • Most common is monocular
32
Q

Predicting Distance Magnification:

A
  • Magnification= required VA/present VA
    • Example:
      ○ Required VA= 6/6 (to watch TV)
      ○ Present VA= 6/18
      ○ Magnification= (6/6)/(6/18)= 3X
  • If you use a LogMAR chart magnification is..
    • Magnification =(1.25)n
    • n=‘number of steps’ = look at number of steps you want px to improve by
      ○ Example:
      § VA is 0.5
      § And 0.1 is required to improve
      § So magnification required is (1.25)4 = 2.5X
      § Cause to go from 0.5 to 0.1, its 4 steps on the chart
  • SO..
  • Need to understand what the px present va is = measured at beginning of test
  • Decide what the required magnification is for the task
  • So px had va of 6/60 and you wanted them to read 6/6, might start off with x10 cause 60/6 = 10
33
Q

Why predict magnification differently at distance and near:

A

Because VA will be different at distance and near so different mag at distance and near

34
Q

Predicting Near Magnification rule of thumb:

A

Distance VA =6/18 then Near VA 18/3= N6

35
Q

Why is it better not to predict near vision from distance vision:

A
  • To measure distance VA you’re using letters but to measure near VA you’re using words/sentences
    • Crowding effect with words = discrepancy at near va = px might read 6/18 in distance but cant read N6 at near
    • Increased VA with sentences
    • Cataracts – effect near va e.g. nuclear sclerotic cataract – can cause myopia – distance va worse than near va and if posterior subcapsular cataract, near va effected more
36
Q

Method of predicting near magnification:

A
  • Measure current Near VA at 25 cm
  • LogMAR charts method:
    • Magnification =(1.25)n
    • n=‘number of steps’
    • For example VA is 0.5 at 25 cm and 0.1 is required then magnification required is (1.25)4 = 2.5X
  • N Notation method:
    • Magnification= Present VA/Required VA
    • Present VA=N16@25 cm Required VA=N8 (to read newspapers)
    • Magnification=16/8=2X
    • E.G. if px has va of n36 and if you want them to read n6 = predicted mag is x6 cause 36/6 = 6
37
Q

What will ability to read for leisure depend on:

A

Acuity and contrast reserve

38
Q

What is example of px requiring separate aid for each task:

A

E.g. 2X HM ( hand magnifier ) newspaper headlines, 4X HM Books, 4X telescope TV

39
Q

Examples of optical magnifier distance:

A

Telescope = monocular or binocular

40
Q

Examples of optical magnifier near:

A
  • Spectacle mounted magnifier
  • Hand Magnifier
  • Stand Magnifier
  • Near Vision telescope
  • Spectacle magnifier
41
Q

What does choice of optical magnifier chosen depend on:

A
  • Distance
  • Task needed
42
Q

Trial of predicted magnification:

A
  • Assess patient’s visual acuity with selected aid of selected magnification
  • EXAMPLE:
    • Decide to get px to read a book
    • They might require 3x illuminated magnifier i.e what you predicted.
    • So you give them a 3x hand illuminated magnifier and give them near vision chart
    • And get px to read what they can with the magnifier
      If px can read N8 with the 3x magnifier, you would increase magnification to 4x
      So give them 4x hand magnifier and get them to read near vision chart again
      And this time px reads N6 or N5 so that’s the aid to dispense to px
      But if with 3x magnifier, px comfortably read n5 then want to give them a lower mag i.e 2x
  • SO increase or decrease the magnification depending on acuity achieved and task requirement
  • Determine whether the aids need to be used with or without Rx
43
Q

Which aids need to be used with or without Rx:

A
  • Distance telescopes usually with Distance Rx and near telescope is near rx
  • HM with Distance Rx
  • SM with Near Rx
44
Q

What magnification is good for maximum VA:

A

Minimal magnification for maximum VA for best FOV

45
Q

What do px’s use when getting px to try and read with the magnifiers:

A

Whatever glasses theyre meant to use at home

46
Q

Loaning aid for home trial - what should you do:

A
  • Explain to patient how to use the aid
    • Which Rx the aid should be used with
    • Should include how to clean aid and change batteries if required
  • If possible training with aid should be give
    • Rehabilitation workers
47
Q

Follow up visits:

A
  • First follow up usually 3 weeks after aid dispensed
  • Subsequent visits: either yearly or when the patient experiences difficulties
  • Find out how good aids are and if px is using them
  • If px having problems with aids call back into clinic to help them
48
Q

Reasons for aid not being successful at follow up and solutions:

A
  • Deterioration in VA
    • Select different possibly stronger aid
    • Suggest non optical aid
  • Aid used incorrectly.
    • E.g. too far away from the eye, inappropriate lighting
    • Give appropriate training/advice
  • Using the aid for a different task than what it was intended for
    • Explain intended use of aid
49
Q

Completing the low vision assessment visit:

A
  • Give patient contact details of practice and encourage patient to call if problems arise
  • Encourage the patient to implement practical tips suggested. E.g. Use felt tip pen
  • Useful contacts
    • RNIB
    • Macular Degeneration Society
    • Social Services Department
  • Talk about technology
  • Talk about registration/social services if applicable
  • Report to GP/optometrist/ophthalmologist where appropriate
50
Q

Remote VI assessments – px at home but optom at clinic:

A
  • Some similarities to face to face but some differences
  • History - similar
  • VA (Distance and Near) with Rx and current LVAs
  • Decide if need stronger or new LVAs
  • Management
    • Signposting
    • LVAs
    • Referral
51
Q

Advantages and disadvantages of LVAs:

A
    • = px doenst have to come in
    • = saves transport costs
    • = convenient for px if vulnerable
    • = cant do every part of test – prescribing low vision needs is hard
    • = refraction is hard
  • Cant try low vision aid L
  • Va – cant use conventional tests and don’t have contrast sensitivity charts that you can use remotely but can measure va remotely – use home acuity test, post near vision chart

Binocular vision, visual impairment and paediatrics (6 decks)

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