visual_acuity_(1) presentation dhir hospital bhiwani.pptx

1. What is he
writing , why
can’t I see?

2. VISUAL ACUITY
Presented by : Dr Nikhil Agrawal , 1ST Year DOMS
Moderated by : Dr Pushkar Dhir
DHIR HOSPITAL AND POSTGRADUATE INSTITUTE OF OPTHALMOLOGY

3. VISION
VISUAL
ACUITY
COLOUR
VISION
CONTRAST
VISUAL
FIELD
STEREOPSIS

4. VISUAL ACUITY

5. What is Visual Acuity ?
• Visual acuity is a measure of the ability of the eyes
to distinguish shapes and the details of the object
at a given distance .
• It is measure of spatial resolution of the visual
processing system
• It is quantified by the minimum dimension that an
object must have in order for the observer to be
able to identify, distinguish or simply detect it.

6. Visual Angle
• It is the angle subtended at the nodal point of the eye by an object in the visual field.
• It is useful and convenient mode of specifying the spatial
(size, position , area)extent of an object.

7. COMPONENTS
MINIMUM VISIBLE RESOLUTION RECOGNITION
Presence/absence of stimulus Identify the spatial characteristics of
target
Resolution + Cognition

8. Visual Milestones
Age Visual Milestone Visual Acuity
3 Months Reaches towards interesting objects
Prefers photographs to patterns
Bifoveal fixation
6/120
6 Months Accommodation well developed
Fusional vergence well developed
Development of fixation to moving objects
6/90-6/24
9 Months Visual differentiation of objects 6/48-6/12
3 Years VA approaches near adult level
Can recognize picture and some letters
6/12-6/6
5 Years Stereopsis fully developed 6/6
3
Years

9. Birth- 3 MONTHS 3-6 MONTHS 6-12 MONTHS 1-3 YEAR 3-5 YEAR SCHOOL GOING
• Blink reflex
• Pupillary light
reflex
• Vestibulo-ocular
reflex
• Eye popping test
• OKN
• VER
• Fixation and
following
• CMS fixation
• Cover test
• Bruckner’s red
reflex test
• Menace reflex
test
• Preferential
looking test
• Catford drum
test
• Cardiff acuity
tests
• Lea’s symbol
• Marble game
test
• STYCAR
• Miniature toy
test
• Boeck candy
test
• Landolt’s C test
• Broken wheel
test
• Pictorial vision
chart test
• Tumbling E test
• HOTV test
• Snellen’s letters
and numbers
• Snellen’s
number and
letters
• LogMAR CHART

10. VA Assessment in Infants
(Birth – 3 months)
• Blink Reflex Test
• Pupillary Light Reflex Test
• Vestibulo-Ocular Reflex: Dolls eye response
• Eye Popping Test
• OKN Test : Optokinetic Nystagmus
• VER :Visually Evoked Response
OKN TEST :10x8 inches diameter , slow phase 0.2s , fast phase 0.1s VER : Only clinically objective test
3 MONTHS OLD ANAYA

11. VA ASSESSMENT FROM
3-6 MONTHS
• Fixation Behavior Test: Infant fixates habitually with better
eye , resists its occlusion .
• CSM Method : Central( corneal light reflex )
Steady (eye movements are smooth)
Maintained( alignment is correct when either
eye is covered )
• Bruckner’s Red Reflex Test
• Cover Test
6 MONTHS OLD ANAYA

12. VA ASSESSMENT IN
6-12 MONTHS
PLT: Preferential Looking Test , Tellers Acuity Card test
Leas Paddles TAC CARDS
12 MONTHS OLD ANANYA

13. • Child prefers to look at a
patterned background .
• VA determined with PLT ranges
from approximately 6/240 in
newborn to 6/60 at 3 months
and 6/6 at 36 months .
Baby can you see me !!
TELLERS ACUITY CARD TEST

14. VA ASSESSMENT IN 6-12 MONTHS
Catford Drum Test:
 It is a detection acuity test.
 Oscillating drum with black dots of various size is
observed .
 Rotation of disc at 60cm evokes pendular
movement .
 Unreliable , as it overestimates the VA.

15. VAASSESSMENTIN
1-3 YEAR OLD
• Cardiff Acuity Card Test: Vanishing optotype test.
11 set of cards are available.
By observing the child’s eye movements and fixations.
• Lea’ Symbols: consists of 4 optotypes arranged
in combination of five per line.
Based on same principle as logMAR

16. VA ASSESSMENT IN 3-5 YEARS
At this age child is able to verbalize and recognize well
• Landolt’s C Test
• Broken Wheel Test
• Tumbling E Test
• HOTV Test
• Pictorical Vision Charts
• Isolated Hand –Fingur Test

17. VA ASSESSMENT IN SCHOOL
CHILDREN AND ADULTS
• SNELLEN’S VISUAL ACUITY CHARTS
• LogMAR CHARTS

19. SNELLEN’S CHART
• Starts with single letter at 6/60 with additional letters on each line progressing
to the 6/4 level.
• Fixed spacing between the lines .
• Nonuniform decrease in size of letters .
• Evenly illuminated
• Measures distance central acuity.
Dr Herman Snellen

20. SNELLEN’S CHART

21. LogMAR CHART
• Logarithm of the Minimum Angle of
Resolution
• Each step indicates increase of 25% in letter
size.
• Letter sizes ratio as we move up is a
constant value of 1.26(0.1log unit steps).
• Incorporated 5 letters in every row.
• Spacing b/w 2 adjacent letters = width of 1
letter.
• Spacing b/w 2 horizontal rows = height of
the letter on lower row.
Designed by Ian Bailey and Jan E. Lovie

22. • Used at a distance of 4 meters .
• 1min of visual angle scores LogMAR of 0 (Log of 1 is
0)
• 2min of visual angle scores LogMAR of 0.3
• As each letter size changes by 0.1logMAR units per
row & there are 5 letters on each row ,therefore
each letter can be assigned value of 0.02.
• LogMAR takes account of every letter that has been
correctly read.

23. VE Equivalents in Different Notation
MAR(min.) Snellen’s VA (ft) Snellen’s VA (m) LogMAR
1.00 20/20 6/6 0
1.5 20/30 6/9 -0.18
2.0 20/40 6/12 -0.3
3.0 20/60 6/18 -0.5
4.0 20/80 6/24 -0.6
6.0 20/120 6/36 -0.78
10.0 20/200 6/60 -1.0
20.0 20/400 6/120 -1.3

24. Early Treatment Diabetic
Retinopathy Study (ETDRS) charts
• Randomized clinical trial designed
to evaluate argon laser
photocoagulation and aspirin
treatment in the management of
patients with early proliferative
diabetic retinopathy(Based on
LogMAR).
• ETDRS equipment and testing have
evolved into what is considered the
gold standard of current-day clinical
trials involving vision testing.

25. Freiburg Visual Acuity Test (FrACT)
• “FrACT” is a visual test battery in
form of a free computer program.
It uses psychometric methods to
provide automated, self-paced
assessment of visual acuity and
contrast sensitivity
• For low vision it can reproducibly
assess CF and even HM.

26. Procedure
• Ensure good natural light or illumination.
• Explain the procedure to the patient.
• Position the patient, sitting or standing, at a distance of 6 meters or adjust
the optotypes according to the available distance .
• Test the eyes one at a time, at first without any spectacles
• The smallest line read is expressed as a fraction, e.g. 6/18.
• If the patient cannot read the top letter at 6m , move him/her closer, 1m at a
time, until the top letter can be seen – the VA will then be recorded as 5/60
or 4/60, etc.

27. Procedure
• If the top letter cannot be read at 1m (1/60), hold up your fingers at varying
distances of less than 1m and check whether the patient can count them. This
is recorded as counting fingers (CF): VA = CF
• If the patient cannot count fingers, wave your hand and check if he/she can see
this. This is recorded as hand movements (HM): VA = HM
• If the patient cannot see hand movements, shine a torch toward the eye and
ask if they can see the light. If they can, record ‘perception of light’ (VA = PL). If
they cannot, record ‘no perception of light’ (VA = NPL).
• Now test the patient while wearing any current distance spectacles or pinhole
occluder and record the VA in each eye separately.
• If the vision improves, it indicates the visual impairment is due to irregularities
in the cornea, a problem in the lens, or refractive error, which is correctable
with spectacles or a new prescription.

28. Having problem reading our discharge
tickets!! You need a near vision
assessment

29. Near Vision Assessment
• Near vision is tested by asking the pt. to
read a near vision chart kept at a distance of
25cm to 35cm.
• Each eye should be tested separately.
• The near vision is recorded as the smallest
type which the pt. can read comfortably.

30. Jaeger’s Chart
Prints are marked from 1 to 7 and
accordingly patient’s acuity is labelled as J1-
J7 .
Eduard Jäger von Jaxtthal

31. Roman Test Types
• Consists of Times Roman fonts
with standard spacing.
• The near vision is recorded as
N5, N6, N8, N10, N12, N18,
N36 and N48.

32. Snellen’s Near Vision Test Types
• Constructed on the same principles as of the distant
types.
• The graded thickness of the letters is about 1/17 of the
distant vision chart letter.
• The letter equivalent to 6/6 line subtend an angle of 5
min. at the average reading distance.

33. References
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4069781/#:~:text=Visual%20
acuity%20(VA)%20is%20a,is%20tested%20at%20a%20time.
• https://www.aao.org/eye-health/tips-prevention/eye-chart-facts-history
• https://michaelbach.de/fract
• https://www.precision-vision.com/articles/what-is-etdrs/
• Khurana – Optics and Refraction

34. That’s how I passed .