For optometry and ophthalmology

1. VA MEASUREMENT AT
DISTANCE AND NEAR
PRESENTED BY
SUJIT KUMAR SHAH
B.OPTOM, 2ND YEAR

2. CONTENT:
Introduction to VA and visual angle
Types of VA charts
Distance vision chart types
Procedure of taking distance VA
VA assessment in LogMAR chart
Near vision chart types
Procedure of taking near VA
References

3. INTRODUCTION
 Visual acuity (VA) is a measure of the
ability of the eye to distinguish shapes
and the details of objects at a given
distance.
 Visual acuity depends on optical and
neural factors. Optical factors of
the eye influence the sharpness of an
image on its retina. Neural factors
include the health and functioning of the
retina, of the neural pathways to the
brain, and of the interpretative faculty of

4.  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.
 In terms of visual angle, visual acuity
is defined as the reciprocal of the
minimum resolvable visual angle
measured in minutes of arc for a
standard test pattern.
acuity = 1/gap size [arc min]

6. OPTOTYPE
 It represents each individual letter,
number or picture on a testing chart.
 Snellen optotype subtends a visual
angle of 5 minute of arc.
 Each smaller component of the letter
subtends visual angle of 1 minute.
 1 minute is the smallest angle for a
person to see 2 separate points.

8. TYPES OF VA CHART
 Snellen chart (most common used chart)
 LogMAR chart (Bailey-Lovie chart)
- Equal numbers of letters per line
- Regular spacing between lines and
letters
- Uniform progression in letter size
 Kay picture test
 Keeler LogMAR
 Cardiff cards
 Lea symbol chart
For children

9. Snellen vision drum LogMAR Chart

10. Distance vision chart types
 Snellen chart
 LogMAR chart
 Tumbling E chart
 Landolt C chart
 ETDRS chart (Early treatment diabetic
retinopathy study)
 Picture charts

11. Snellen chart
 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
at top lines should be read clearly at
distance of 60 m.

12. Procedure of taking distance
VA
 Ask the patient to sit at 6 meters from
the Snellen’s chart.
 Chart should be properly illuminated.
Patient made to wear trial frame.
 Ask the patient to read with one eye
from top letter while the contra lateral
eye is closed gently with patient arm
or with occuluder in trial frame.

13. Interpretation
 Depending on the smallest line patient
can read from the distance of 6 meters,
VA is recorded as 6/6, 6/9, 6/12, 6,24,
6/36 and 6/60.
- Numerator: Distance of the patient
from the chart
- Denominator: Smallest letter read
accurately
 eg: VA 6/12 means that the patient can
read optotype at 6 m while the normal
person can read the same letter from 12
m distance.

14.  If the patient cannot see the top line from
6m, he is asked to walk towards the
chart till he can read topline.
 Depending on the distance at which
patient can read the topline, the VA is
recorded as 5/60, 4/60, 3/60, 2/60, 1/60.
 If patient is not able to read top line even
at 1m , he is asked to count fingers of
examiner and his vision is recorded as
CF3FT, CF2FT, CF1FT or CF close to
face.
 If patient is not able to count finger close
to face then examiner waves his hand
and ask patient whether he is able to see
hand movement or not. Visual acuity the

15.  When patient cannot distinguish hand
movement, 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 the examiner throw the light from
four directions( nasal, superior,
temporal, inferior)

16.  Landolt ring chart: This chart
containing a series of broken rings,
with 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

17. VA assessment in LogMAR
chart
 The LogMAR chart is designed to enable
more accurate estimates of acuity as
compared to other acuity charts.
 The LogMAR charts are designed for 4m
direct distance and its letter subtends an
angle of 5 minute of arc at 40m distance.
 Each line of LogMAR chart comprises
the same number of test letters. The
Sloan font is used.
 Letter size varies from line to line
logarithmically as does the spacing
between between line.

18.  While using the LogMAR chart, visual
acuity is scored with reference to the
logarithm of minimum angle of
resolution, as the chart name suggests.
An observer who can resolve details as
small as 1 minute of visual angle scores
LogMAR 0, since the base-10 logarithm
is 0.
 A Snellen score of 6/6 (20/20), indicating
that an observer can resolve as small as
1 minute of visual angle, corresponds to
a LogMAR of 0.
 Similarly, 6/12 (20/40) indicating that an
observer can resolve details as small as
2 minute of arc of visual angle,
corresponds to a LogMAR of 0.3

19.  Each letter has a score value of 0.02 log
units. Since there are 5 letters per line,
the total for a line on the LogMAR chart
represents a change of 0.1 log units.
 The formula used in calculating the score
is:
LogMAR VA = 0.1+ LogMAR value of
best line read - 0.02* (number of
optotype read)
 Given that each line has 5 optotypes, the
equivalent formula is:
LogMAR VA= LogMAR value of the
best line read + 0.02* (number of

21. POINTS TO BE NOTED...!!
 Zero LogMAR indicates standard
vision.
 Positive values indicate poor vision.
 Negative values indicate good vision.
Q. Who invented LogMAR chart ?

22. Pinhole test (Interpretation)
 If patient vision is improved with
pinhole, 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 VA may be due to
corneal opacity or lenticular opacity
occupying papillary area or macular
pathology.

23. Near vision chart types
 Snellen near vision chart
 Jaegar chart
 Roman test type

24.  Near vision tests the ability of a patient to see
clearly at a normal reading distance with a
printed handheld card.
 Testing distance – 40 cm (16 inches)
 Testing charts
Roman test type:
-Most commonly used chart is N notation
- Each point is 1/72nd of an inch.
- Usually in Times New Roman font.
- Vision is recorded as N6, N8, N10, N12,
N14, N18, N24, N36
Jaegar’s chart
- Prints are marked from 1 to 7 and
patient’s acuity is easured as J1 to J7
depending on the print patient can read.

25. Snellen’s near vision chart
- Conventional Snellen distance VA
chart is reduced by 1/17th times.

26. Procedure of taking near VA
 Ask the patient to sit with is back
straight.
 If the patient is using glasses for
distance, the same number will be put on
the trial frame. Occulude one eye with
occuluder
 Ask patient to hold the near vision chart
by his right hand at a distance of 25 to
33 cm.
 Note the near vision as per the letter
read

27. References
 Handbook of investigative
ophthalmology
 https://www.indiamart.com/proddetail/
near-vision-chart-
2851768326862.html
 https://www.slideshare.net/SamPonraj/
vision-assessment-23973506
 https://en.wikipedia.org/wiki/Snellen_c
hart
 https://www.oscarwylee.com.au/eye-