This document discusses vision assessment and various tests used to evaluate visual function. It describes visual acuity tests including Snellen, Landolt C, and ETDRS charts to measure resolving power and smallest details the eye can see at various distances. Near vision, dark adaptation, contrast sensitivity, and color vision are also assessed. Standard procedures are outlined for administering visual acuity tests and interpreting the results.

1. VISION ASSESSMENT
Mahantesh.B HOD of optometry

2. What is vision ?
 Resolving power of the eye or the ability to see two
separate objects as separate.

3. Vision Assessment of visual function
 visual perception
 Visual Acuity
 Dark adaptation
 Contrast sensitivity

4. Visual perception
 Forms of visual perception are form sense ,
the field of vision, the light sense and the
colour sense .

5. 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.
 Distance vision
 Near vision
 Pin hole vision
 Colour vision

6. Distance vision
 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.

7. Distance vision charts types
 Snellen
 Tumbling E
 Landolt C
 ETDRS
 Picture chart

8. Snellen charts
 The original eye chart
designed in the 1860’s by the
Dutch eye doctor Hermann
Snellen. The first line on this
chart is a giant letter E. You
read the chart from top to
bottom, left to right covering
one eye at a time.

9. Tumbling E charts
 his type of eye chart is used
for children that are too
small to read or adults with
reading or speaking
difficulties. The patient is
asked to lift their hand up,
down, to the left or right
depending on the image
orientation of the letter E
they see on the chart.

10. Landolt C charts
 Edmund Landolt, a Swiss
ophthalmologist, created this
visual acuity chart. This eye
chart, which is similar to the
Tumbling E chart, uses a
Landolt broken ring symbol in
various orientations. The
Landolt C chart is a way to
check vision for illiterate or
mute patients.

11. ETDRS charts
 The Early Treatment
Diabetic Retinopathy Study
helped develop
standardization for both
visual acuity testing and eye
chart design. The ETDRS is
accepted by The National
Eye Institute and the FDA as
the mandated standard for
clinical eye test trials
worldwide.

12. Picture chart
 Picture chart. Used to test
visual acuity in preliterate
children 2 to 4 years of age
and in moderately mentally
impaired adults. Available for
both distance and near
testing.

13. 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.

14. Principal
 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 ar36, 24,18,12,9,6, respectively
 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

15. Procedure of testing
Distance of 6 mts is taken as at this distance it is
assumed that the rays are almost parallel and patient
exert minimum accommodation

16. Continue
 The chart should be properly illuminated
 Patient made to wear trial frame.
 It is adjusted according to patient inter pupillary
distance
 Ask the patient to read with one eye from the top
letter while the contra lateral eye is closed with
occlude in the trial frame
 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.

17. Continue
 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, respectively
 If patient is not able to read top line even at the
distance of 3 mts he is asked to count fingers of
examiner and his vision is recorded as CF3mtr, CF
2mtr, CF1mtr OR CFCF

18. Continue
 If patient not able to count examiner finger close to face
then examiner moves his hand and asks patient whether he
is able to see hand movement or not. Visual acuity then
recorded as HM+/HM-
 IF NOT the examiner notes whether the patient can
perceive light (PL) or not
 . If he perceive light it is noted as PL +ve 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

19. Pin Hole Test
 If patient vision is improved with
pin hole it means the poor acuity is
due to refractive error.
 If not improve means may be due
to structural or organic cause.
 If reduced the poor visual acuity
may be due to corneal opacity or
Lanticular opacity occupying
papillary area or macular
pathology.

20. Near vision
 Snellen near vision chart
 Jaeger near chart
 Roman near test type

21. Procedure of testing
 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.

22. Dark adaptation
 Threshold (DAT) is a vision test that measures the
adjustment of the eye occurring under low levels of
illumination
 measurement of least luminance required to produce a
visual sensation

23. Contrast sensitivity
 Ability of eye to perceive
slight changes in
luminance between regions
not separated by definite
borders