Visual acuity is measured using charts with letters of decreasing size, with the Snellen chart being most common. It represents the sharpness of vision and is recorded using a fraction where the numerator is the test distance in feet and the denominator is the smallest line read on the chart. Additional tests include visual fields, color vision, and pinhole tests to determine if vision problems are due to refractive errors or other issues. Color vision is assessed using plates like Ishihara that people with normal color vision can interpret but those with defects cannot.

1. Dr. Mohd Najmussadiq Khan
M S (Ophth) DiSSO(ESASO)

2. VISUAL ACUITY--
 Visual acuity is the ability to distinguish
details and shape of the objects. It's
functional assessment of fovea.
 Total number of cones is 6.5 to 7 million but
cones of fovea are 147000/mm2.
 Cones in 3 mm from fovea are 6000/mm2.
 Cones in 10 mm from fovea are 3000/mm2.

3. Visual acuity
charts

6. Snellen Charts:--

8. Snellen Charts:--
 Letter of graduated sizes which making an
angle of 5 minute and each part of the letter
making an angle of 1 minute, best letter is E
(each portion of it is separated by constant
1o and it subtends at 5o).

9. Visual angle in Visual acuity
charts

10.  Visual acuity is recorded by 2 numbers e.g. 6/18.
 Dominator is distance at which the letter subtends an angle
of 5o.
 Usually the patient sits on a chair at 6 meters from the test
chart closing an eye each time to record visual acuity of each
eye if patient using glasses---first record without glasses then
with them.
 The last line that the patient seen determines his or her
visual acuity.
 If the patient did not read all the letter if the line e.g. two
letter of line 6 visual acuity is 6/6-2
 If patient did not see 1st line --- reduce the distance (5/60 ,
4/60 …..).
 Counting fingers (C.F):-
 Hand movement (H.M):-

11.  If person is unable of count finger --- record the
distance at which he can recognize hand
movements.
 Light projection (PR):-It’s the ability to detect
the direction of light (function test for retinal
periphery and optic nerve).
 Light perception (perception of light) (P.L):-
Can patient perceive light if no P.L ----blind. Try
not to use the word blind ----say no P.L

12. HOW TO TEST NEAR VISION--
 measurement of near vision is not as
accurate as distance vision.
 Test distance charts are 35cm; many test
charts are used as Jaeger charts J1, J2,
J3…..American ophthalmologic society N1,
N2 ….

13. HOW TO TEST VISUAL ACUITY IN
CHILDERN--
 4 year or > usually cooperative on Snellen
charts with familiar objects or E cards.
 By throwing coins on the floor--- let the child
pick them up.
 Using a rotating drum with alternating strips
of black and white--- this rotating movement
will produce of opticokinetic nystagmus
(OKN) in normal vision.
 Infants are taking interest in surrounding
light.

14. Hundreds and thousands’ sweet
test

15. Preferential looking with Cardiff
cards

16. Pinhole test:-
 Measurement of visual acuity with patient
seeing test letters through a small opening
in an opaque shield.
 It's to differentiate whether subnormal
vision is due to refractive error or pathology
in the eye.

17. Pinhole--

18. Visual field:-
 It’s the area simultaneously visible to one eye without
movement measured by perimeter 33 cm from the eye. It can
be recorded by many instruments or clinically by the
confrontation test.
 It gives rough estimation of visual field .
 The examiner sits facing the patient at 1 meter in a good
illumination.
 Ask the patient to close one eye with his fingers the examiner
closes right eye --- examiner closes left .
 The examiner brings his hand slowly from the periphery with
1 or 2 fingers extended --- midway between examiner and
patient .
 When the examiner and patient have normal vision they
should recognize number of finger at same time --- test
temporal, nasal, superior and inferior fields.

19. Normal visual field as plotted by
Bjerrum tangent screen

20. Confrontation visual field
testing

21. Kinetic visual
field testing
with
Goldmann
perimeter

22. Static perimeter: Friedman
analyzer

24. COLOUR VISION
It’s the function of cones and there are three type of
cones with photo pigments .
 Long wave length sensitive cones---red sensitive
 Middle wave length sensitive cones---green
sensitive
 Short wave length sensitive cones---blue sensitive
The red and green cones are 5 time more than blue
cones. The color vision is trichromatic (mixing of
the 3 primary colors to give 150 – 200 colors
(Trichromatism)

25. COLOR VISION DEFECT--
 Sex linked recessive disorder its 8% in male
and 0.4% in female.
 Color deficient not color blind.
 There is no treatment, it bilateral,
stationary, normal Fundus.
 They are unfit for some jobs as railway
engine drivers, laboratory technician.

26. Type of color defect:-
 Red deficient--- protanomaly Protanopia
protanopes
 Green deficient--- deutanomaly
Deuterdeutanopes
 Blue deficient--- tritanomaly
tritanopes
 Its trichromatic 3 pigments present but one is
abnormal.

27. Acquired :-
Cause :-
 degeneration of cons
 optic nerve disease e.g. neuritis
 visual cortex defects
 change in optical media e.g. cataract
 it is may be unilateral or bilateral,
progressive and may curable if disease
recovered .

28. Methods of testing colour vision :-
 Test plates
 Ischihara plates
 lantern test
 Hue discrimination test (100 hue test )
 D 15 test

29. Ishihara colour plates:
 Right: with a green
filter.
 Left: without the
green filter.

30. Ischihara plates