Functional visual acuity FVA

Question 1

Visual acuity

Answer 1

A measure of the ability of the eye to distinguish shapes and the details of objects at a given distance. It is assessed by determining the finest spacial detail that the visual system can discriminate.

Question 2

Importance of consistency in VA

Answer 2

It is important to assess VA in a consistent way in order to detect any changes in vision.

Question 3

How is VA assessed components

Answer 3

It is assessed by determining the finest spacial detail that the visual system can discriminate
Ø Ability to resolve a pattern into spatially separated elements
Ø Denotes the size of detail that can just be resolved by an individual = Visual resolution

Question 4

Visual progress of newborn

Answer 4

6/240 VA

on single optotypes

Question 5

Visual progress of 1 month old

Answer 5

6/180 – 6/90 VA

on single optotypes

Question 6

Visual progress of 4-6 month old

Answer 6

6/18 – 6/6 VA

on single optotypes

Question 7

Visual progress of 3 year old

Answer 7

6/6 VA

on single optotypes

Question 8

Study- VA in children is Sydney in lecture slides

Answer 8

Findings- Normal population distribution of visual acuity by age group using monocular Teller Acuity Cards II.
Caucasian population
Vision screening 4-5 year olds
0.2 logmar
Normal population distribution of visual acuity by age group using monocular Teller Acuity Cards II.
Caucasian population

Question 9

Study- ethnicity and monocular VA

Answer 9

-1722 African-American and Hispanic children aged 30 to 72 months.

Question 10

Findings from African American and hispanic children study

Answer 10

There were significant differences in monocular visual acuity between African-American and Hispanic children within the specified age range.
Further analysis revealed potential disparities in visual acuity development and outcomes based on ethnicity.
The study suggests the need for tailored interventions or screenings to address any identified discrepancies in visual acuity among children from different ethnic backgrounds.

Question 11

Visual acuity standards

Answer 11

Normative Paediatric VA is not as good as Adult VA

Vision screening referral criteria for children worse than 0.2 logMAR

Normative adult VA: 0.0 logMAR - many achieve better than this

Question 12

Certificate of visual impairment

Answer 12

Severe sight impairment (Blind) – VA < 1.3 logMAR (3/60)

Sight impairment (partially sighted) – VA 1.0 logMAR (6/60) or less dependent on visual fields

Question 13

Functional vision assessment

Answer 13

Functional vision refers to what a person can see and how an individual uses whatever vision he or she has in everyday life.
FVA often required in adults or children with special needs with multiple and complex disabilities and when conventional VA tests are not possible.

Question 14

Challenges with conventional VA testing

Answer 14

Ø Crowded LogMAR tests not always possible in these patients . Especially at 3 m
Ø FCPL and Cardiff cards don’t always stimulate vision. Children may not be interested in these
Ø Clinician cannot easily relate findings of a visual acuity score to real life situations
Ø When its low levels of acuity scorings it is difficult to give parents / carers / teachers any useful information about the vision measured which they can use to assist the child’s learning.

Question 15

Study- A test battery of child development for examining functional vision ABCDEFV
components

Answer 15

A battery of 22 tests
Assessment of children’s functional visual capacities between birth - 4 years of age
Assesses:
sensory visual measures:
perceptual, motor, spatial and cognitive aspects of visual function

Question 16

ABCDEFV test drawbacks

Answer 16

There are 22 tests- not functional because too many and child may have SEN needs and can’t focus for extended time

Question 17

The Bradford visual function box

Answer 17

The box (BVFB) comprises a selection of items (small toys) of different size and colour, which are presented to the child and the response observed
The aim of this study was to establish its inter-test validity in children with severe learning disability
The visual function of 22 children with severe learning disability was assessed using the BVFB

Question 18

BVF test fixation targets

Answer 18

6 mm Red Bead
10 mm Green Bead
14 mm Stripy Bead
21 mm Fish Bead
28 mm Gold Bubble
40 mm Frog
65 mm Pink Spiky Ball
70 mm Pink Chicken
90 mm Fan
120mm Baby Shape Book

Question 19

BVD test recording results

Answer 19

VA c/sgls BVFB
RE fix and follow 6mm red bead at 30cm

LE fix and follow 10mm green bead at 30cm

Reliabilty score RE- 3 LE- 3

Question 20

Reliability score of BVF test

Answer 20

1= variable response—uncertain of result,
2= reasonable response—somewhat certain
of results
3= excellent response—very certain of result

Question 21

Assessment proforma BVF test

Answer 21

• recognising mum/ family members, can find toy, tell if light or dark
  -what toys do they enjoy playing with and what do they enjoy doing
  -is there variability with their vision
  -hearing concerns?
  -hand movements possible
  -head control possible- turn head to follow toy
  -visual memory- look for dropped toy

Question 22

Observations BVF test

Answer 22

Light perception- bright light in dark room, blink reflex
Facial perception- follow and look, return silent smile
Fixation
FCPL cards, black and white books 1-4
How long to hold fixation and visual attention

Question 23

Repeatabilty BVF test-is it reliable when documenting visual function

Answer 23

Pillling et al (2016) showed good repeatability between two examiners.
When a difference was noted the reliability score was 1 (variable response)
Conclusion: The BVFB is a reliable tool to document visual function

Question 24

Tip for BVF test

Answer 24

avoid noisy toys as this will give cues

Question 25

Functional vision assessment in light and dark

Answer 25

Fixes pen torch
Follows pen torch horizontally
Follows pen torch vertically
Fixes large white light
Follows large white light horizontally
Follows large white light vertically

Question 26

Reactions to changes in lighting

Answer 26

Daylight- Reacts to room lights being turned on/off
Darkened room- Reacts to room lights being turned on/off

Question 27

Note

Answer 27

Toys and targets graded by size 1-5
Fix and follows horizontally and vertically

Question 28

Pupil reactions AND blink

Answer 28

React to direct stimulation
Reacts to consensual light stimulation
Relative afferent pupillary defect RAPD
Description i.e. anisocoria
Blink reflex
Blinks to approaching silent object

Question 29

FVA and OKN drum

Answer 29

can use OKN drum as this can assess optiokinetic nystagmus horizontally and vertically.
can do swinging baby/ dolls head movements and visual field to confrontation with toys

Question 30

Forced choice preferential looking techniques FCPL

Answer 30

Square wave grating – black and white stripes of equal width

Question 31

FCPL method

Answer 31

Keller Cards – test distance is 38cm
Ideal age – 8 weeks to 12 months
Present card and observe whether infant looks toward the grating – repeat with finer gratings
Staircase procedure
Vision is recorded in cycles/degree – also equivalences in logMAR & Snellen

Question 32

FCPL techniques

Answer 32

Allows measurement of vision in infants and very young children
Delayed visual maturation – infants who appear blind when seen before 10-15 weeks
Early detection of gross amblyopia
Monitoring progress of children being treated for infantile cataracts and associated deprivation amblyopia
Patients with mental/ physical disability

Question 33

Grating can…

Answer 33

overestimate vision when compared with conventional tests which assess recognition acuity

Question 34

Minimal angle of resolution=

Answer 34

Resolving power of the eye minus smallest stimulus discernible

Question 35

What do you do if VA is < 1.0 logMAR (6/60)?

Answer 35

Reduced the test distance i.e. move the test closer
Use LogMAR Crowded Test and bring the 0.8 (6/38) size letter closer i.e. 1.5m or as close as required for the patient to identify the letter
Ask the patient if they can see the letters better by fixing eccentrically i.e. by not looking directly at the letter. You may notice the eye is not centred. The patient is not able to fix with their fovea
Patient’s fixation may be wandering as they try to locate optimum vision i.e. wandering fixation
May also adopt an abnormal head posture
Wandering fixation pts have poorer VA and AHP

Question 36

If VA is less than 1/60 test options are..

Answer 36

counting fingers, hand movements, perception of light, presence of OKN and EDTs

Question 37

Formula for reducing VA test distance

Answer 37

Formulae: 1/V = M*(1/m)

V = Visual acuity
M = size of the letter optotype
m = testing distance in metres

Oduntan (2006) A practical logMAR near reference table for low vision practitioners: design and applications. S Afr Optom. 65:157-162. and table in pp

LogMAR ratio is 1.2589