using a snellen chart 1.4

Question 1

what is a standard observer?

Answer 1

the standard observer has a visual acuity that just allows him\her to identify a letter with a stroke width subtending 1 min of arc

Question 2

what is form vision?

Answer 2

the ability to recognise an object from its shape/form

Question 3

what is resolution?

Answer 3

the ability to detect fine details

Question 4

what does recognition of letters depend on ?

Answer 4

recognition of letters as they get smaller requires both form vision and resolution

Question 5

what is visual acuity?

Answer 5

smallest line of letters read with spectacles or CL

Question 6

what is unaided vision ?

Answer 6

smallest line of letters read with unaided eye

make sure to record if its both eyes ( binocular ) or one eye ( monocular )

Question 7

what is Binocular summation ?

Answer 7

advantage when preforming tasks with both eyes

Question 8

what is snellen fraction v ?

Answer 8

V= testing distance at 6m / distance at which the limbs of last letter read correctly subtends at 1min of arc and angular height of last line of letters correctly identified is 5 min of arc

Question 9

what is minimum angle of resolution ( MAR) ?

Answer 9

angular separation of two points or lines at the resolution acuity limit

Question 10

what is MAR for a standard observer?

Answer 10

1 min of arc

Question 11

what is the resolution acuity limit?

Answer 11

point where we can just about detect difference between s lines before we loose separation

Question 12

what is decimal v notation?

Answer 12

the snellen fraction can be written as a decimal
6/5 = 1.2
6/6 =1

Question 13

what is the formula of decimal V?

Answer 13

V=1/MAR

Question 14

how to record snellen chart?

Answer 14

. if 3 letters are incorrectly identified on the 6/5 line recored as 6/5-3

Question 15

what to do if visual acuity is below 6/60?

Answer 15

. reduce distance to 3m
. counting fingers - should be at less than 1m
. hand movement
. perception of light