This document discusses visual acuity testing procedures. It defines visual acuity as the ability to see details and outlines three types: minimum detectable, minimum separable, and minimum recognizable. Factors like illumination, contrast and refractive error can affect visual acuity. The standard test is the Snellen chart at 6 meters, where the smallest line read corresponds to the visual acuity score in meters. Additional notation is used if the top line can't be read at 6 meters or if only hand motions or light perception is visible.

2. BY. Farah Naheed
B.Sc (Hons.)Optometry and Orthoptics
Pakistan Institute Of Ophthalmology , Al-Shifa Trust
Eye Hospital Rawalpindi.

3.  Visual Acuity
 Visual Angle
 Basics of Acuity charts
 Acuity charts
 Types of Visual Acuity
 Factors Affecting V/A
 Clinical Measurements
 Procedure of testing V/A

6. Resolving power of the eye
or the ability to see two separate objects as
separate.

7. The angle subtended at the nodal point of the
eye by the physical dimensions of an object in
the visual field.
Nodal Point…?

8.  The distant acuity is usually tested by snellen chart.
 Consist of a series of black capital letters on a white
board.
 Each letters fits in a square.
 Assume 5x5 grid for letters with detail separation of
1/5 of letter size.

10.  Snellen chart
 E-chart
 C-chart(Landolt ring or Broken ring chart)

12.  Minimum Detectable ( visible)
 Minimum Separable (resolution)
 Minimum Recognizable (recognition)
 Minimum Discriminable ( hyperacuity)

13.  It is also called Visible.
 Ability to determine whether an object is
present or absent in a visual field.
 The min. angle of detection is 1 seconds of
arc.

14. B) A White Dot against Black BGA) A Black Dot against White BG

15.  It is also called Resolution.
 Ability to determine a group of points or lines as
separate objects.
 The min. angle of resolution is 30-60 seconds of an
arc.

16. It is also called Recognition.
It involves discrimination of the spatial
characteristics of the test pattern with which he has
previous experience.
Forexample:
Identification of faces etc.

17.  It is also called Hyperacuity.
 Ability to determine whether or not two
parallel and straight lines are aligned.
Forexample: Vernier Acuity.

19. Overall
 Illumination of test object
 Contrast of letters
 Pupil size
 Cognitive ability
 Refractive error

21.  Criteria:
 Normal testing distance (distance VA): 6m
 Illuminated visual acuity chart.
 Proper room illumination.
 Steps:
 Unaided VA
 Aided VA
 Pinhole VA

22. 1) For testing distant visual acuity, the patient is
seated at a distance of 6m from the Snellen’s chart.
2) The patient is asked to read the chart with each eye
separately.
3) When the patient is able to read up to 6 m line, the
visual acuity is recorded as 6/6, which is normal.

23. 4) Depending upon the smallest line which the
patient can read from the distance of 6 m, his
vision is recorded as 6/9, 6/12, 6/18, 6/24, 6/36
and 6/60, respectively.
5) If he cannot see the top line from 6 m, he is asked
to slowly walk towards the chart till he can read
the top line. Depending upon the distance at which
he can read the top line, his vision is recorded as
5/60, 4/60, 3/60, 2/60 and 1/60, respectively.
6) If the patient is unable to read the top line even
from 1 m, he is asked to count fingers (CF) of the
examiner. His vision is recorded as CF-3’,CF-2’,

24. 7) When the patient fails to count fingers, the
examiner moves his hand close to the patient’s
face. If he can appreciate the hand movements
(HM), visual acuity is recorded as HM positive.
8) When the patient cannot distinguish the hand
movements, he is taken into the dark room and a
light is focused on his eye and he is asked to say
when the light is on and when it is off. If he
succeeds in doing this,If vision is recorded as PL
+ve and if not it is recorded as PL –ve.