1. Vision Assessment
Dr Rajvin Samuel
1 st yr pg

2. • Vision assessment in adults
• Visual assessment in children
• Retinal function tests
• Visual field examination

3. 1. Examination of Vision
Assessment of visual function
• Forms of visual perception are form
sense , the field of vision, the light
sense and the colour sense .

4. • Visual Acuity
• Visual field examination with confrontation
test, perimetry (kinetic and static)
• Dark adaptation – measurement of least
luminance required to produce a visual
sensation
• Contrast sensitivity – is measurement of
the smallest distinguishable contrast ,it is
assessment of quality of vision
• Colour vision –with lantern test (Edridge
green lantern) and Isochromatic charts

5. Visual Acuity
• The principal of assessment is measurement of spatial resolution of
the eye i.e. an estimation of ability of eye to discriminate between
two points.
DISTANCE VISION
Two distance point can be visible as separate
only when they subtend an angle of 1 minute
at the nodal point of eye.
5

6. Visual Acuity
• Definition-
It is defined as the measure of the smallest
retinal image which can be appreciated with
reference to its shape and size .it is actually
measure of form sense.
Subjective examination of the function of eye
• Central or direct vision
• Distance vision with Snellen test type
• Near vision with Snellen test type or Jaeger’s
test type
6

7. Snellen chart
Principle
• Each individual letter subtends an angle of 5 minutes
and each component of letter subtends an angle of 1
minute at the nodal point of eye from the distance in
meters written as numerical.
• Snellen chart is having different number of letters in
different rows and the letter at top line should be read
clearly at distance of 60 m. similarly the letters at
subsequent lines as are read at 36, 24,18,12,9,6,5mts
respectively
• Numerical convention is used for recording visual acuity.
In fraction, the numerator is the distance at which the
patient is sitting from chart and the denominator is the
distance at which person (with normal vision) should be
able to read the last line that person is able to read.
7

8. Trial frame
Occluder and Pin Hole
Snellen Chart

9. Procedure of testing
• Patient is seated at the distance of 6 meters
from Snellen’s chart (distance of 6 mts is taken
as at this distance it is assumed that the rays are
almost parallel and patient exert minimum
accommodation)
• The chart should be properly illuminated at
minimum of 20 feet candles. Patient made to
wear trial frame. It is adjusted according to
patient inter pupillary distance. 9

10. Procedure of testing
• Ask the patient to read with one eye from the top letter
while the contra lateral eye is closed gently with the
patient arm or with occulder in the trial frame.
• Now patient is asked to reads the Snellen’s chart and
depending upon the smallest line which the patient can
read from distance of 6mts his vision is recorded as 6/6,
6/9 ,6/12,6/18, 6/24, 6/36, 6/60.
• But if patient is not able to see the top line from 6mts he
is asked to come towards Snellen’s charts step by step
and vision recorded at 5,4, 3, 2, 1 mts and noted as
5/60,4/60,3/60,2/60,1/60 respectively
10

11. Procedure of testing
• If patient is not able to read top line even at the
distance of 1 mts he is asked to count fingers of
examiner and his vision is recorded as CF3FT,
CF 2FT, CF1FT OR CF close to face .
• If patient not able to count examiner finger close
to face then examiner waves or moves his hand
and asks patient whether he is able to see hand
movement or not. Visual acuity then recorded as
HM+ 11

12. Procedure of testing
• When patient cannot distinguish hand
movements the examiner notes whether the
patient can perceive light (PL) or not. If he
perceive light it is noted as PL +ve otherwise as
PL-ve. Also examiner then throw the light from
four directions (nasal, superior, temporal,
inferior)
• and record accordingly. if present patient
perceive light from all directions it is marked as
PR (Projection of rays ) present or else mark as
absent or defective. The test is repeated for the
other eye in similar fashion
12

13. Procedure of testing
• English, other language charts
• Landolt ring chart
This is the chart containing a series of broken
rings, with each gap subtending an angle of 1
minute at nodal point at a given distance.
It is used in illiterate patients.
• E-chart – used in illiterate patients
• Simple picture charts for children.6 July 2013Dr Sanjay Shrivastava 13

14. Pin Hole Test
Interpretation
• If patient vision is improved with pin hole it
means the poor acuity is due to refractive error.
• If static acuity means may be due to structural or
organic cause.
• If reduced the poor visual acuity may be due to
corneal opacity or lenticular opacity occupying
papillary area or macular pathology.

15. Near vision
Charts for testing near vision are
1) Snellen near vision chart -
2) Jaeger chart
3) Roman test type
• Ask the patient to sit with his back to the
• light
• If the patient is using glasses for distance
• the same number will be put on the trial frame. Occlude one eye
with an occulder
• Ask the patient to hold the near vision by his right hand at a distance
of 25 to 33 cms.
• Note the near vision as per the letter read
• Repeat the test for the other eye. 15

16. Method of recording Near vision
• Ask the patient to sit with his back to the light
• If the patient is using glasses for distance the
same number will be put on the trial frame.
Occlude one eye with an occulder
• Ask the patient to hold the near vision by his
right hand at a distance of 25 to 33 cms.
• Note the near vision as per the letter read
• Repeat the test for the other eye.

17. Contrast sensitivty
• Ability of eye to perceive slight changes in
luminance between regions not separated by
definite borders.
• Types :
Letter contrast sensitivity
contrast sensitivity gratings
Also distances between repeats of patterns taken into
account

18. Letter contrast Contrast sensitivity
sensitivity grating

19. Visual Assessment in Children
• Preliminary Tests :
• Preliminary Tests Begin with general observation of the child.
• Hirschberg’s Test: Gross check of ocular alignment.
• Pupils: size, shape, reaction.
• Ocular motility.
• Fixation pattern.
Classification :
• Infants: < age 1 yr
• Toddlers: 1 yr – 4 yrs
• Children: 5 yrs – 14 yrs
• Adolescence: 15 yrs – 17 yrs
• Adults: 18 yrs and above

20. • VA measurements (Infants) :
• VA measurements (Infants) Optokinetic Nystagmus:
Nystagmus is elicited by passing a drum with black and white
stripes. If normal vision is present, rail-road nystagmus will be
seen.
•
Preferential Looking Test:
Child is presented with two adjacent stimulus fields, one is
striped and the other is a plain background. The child will look
at the striped pattern for a longer time. The location of the
stripes is shifted randomly from right to left. Fineness of the
stripes is reduced till the infant can no longer differentiate the
stripes and the background.
•

21. • Visually Evoked Response: Useful in assessing visual
function in infants. It is the electroencephalographic recording
made from the occipital lobe in response to visual stimuli.
Flash VER determines the integrity of macular and visual
pathway functions. Pattern VER depends on form sense and
gives rough estimate of the VA.
•
Indirect assessment of VA: Blink reflex in response to
sound. Menace reflex i.e. closure of eyes on approaching of
object if vision is normal. Fixation pattern i.e. Central / Steady
/ Maintained. Monocular behaviour: resists occlusion on
covering good eye.

22. • VA measurements (1-2 yrs) :
• Marble game test: Child is asked to place marbles in the holes of the box.
Not intended to measure the visual acuity, but the monocular visual
functioning. Vision is noted being ‘useful’ or ‘less useful’.
• Sheridan’s ball test: Series of balls of progressively smaller sizes used. Balls
rolled on grey or white background, smallest size which the child picks
gives the estimation of vision
• VA measurements (3-5 yrs) :
Tumbling E test: Consists of different sizes of E with 4 directions. Child
asked to identify the correct direction.
Sjogren’s hand test: Similar to Tumbling E test. Consists of picture of hand
in 4 different directions.
Landolt’s C test / Broken wheel test: Pair of cars of progressively smaller
sizes, one of it with a broken wheel is shown. Child asked to identify the
one with broken wheel.

23. • VA measurements (3-5 yrs) :
• Sheridan-Gardiner HOTV test: Child is handed a card of HOTV. Asked to
match the letters on the chart. Snellen's equivalent 6/60 – 6/6 can be
estimated.
• Boek candy bead test: Child asked to match beads at 40 cms. Snellen’s VA
of 20/200 can be estimated.
• Light home picture cards: Performed at 10 feet distance. Contains apple,
house and umbrella arranged in Snellen's equivalent 20/200 – 20/10. Child
asked to identify pictures in each line.
• Kay picture tests : Child is given set of pictures in hand. Similar pictures
shown at 10 feet distance on a log MAR chart. Snellen’s equivalent 20/200
– 20/20 can be measured.

24. Retinal function tests
• Amsler’s grid
• Light perception test
• Projection of rays
• Photostress test
• Two light discrimination
• Maddox rod test
• Entopic visualisation
• Laser inerferometry
• Potential acuity meter
• Colour perception

25. Amsler’s grid

26. Colour vision
Pseudo isochromic charts
Farnsworth D 15 Test
Anomaloscope

27. • Maddox rod test
• Entopic visualisation

28. • Potential acuity meter
• Laser interferometry