#12. Central vision. Visual acuity. Examination of visual acuity. Visual charts.

Question 1

What is CENTRAL VISION?

Answer 1

• The Eye’s BEST Vision!
• Used for reading / discriminating FINE Detail / Colour
• STIMULATION of the FOVEA + MACULAR AREA, where MOST of the PHOTORECEPTORS are located

Question 2

What is VISUAL ACUITY?

Answer 2

• OBJECTIVE MEASURE of what a person can see

Question 3

What are the 2 METHODS of EXAMINING the VISUAL ACUITY?

Answer 3

1) SNELLEN’s TEST

2) LogMar Test

Question 4

Explain the SNELLEN’s TEST

Answer 4

• Snellen’s Vision is measured at 6m
• It has letters, but versions with ILLITERATE E & Numbers
• 6/6 Line is considered NORMAL Vision
• IF Px can read the LOWER Lines = 6/5 or 6/4 they have BETTER Vision than Normal
• NUMERATOR = Distance FROM the Snellen’s Chart
• Test EACH eye SEPARATELY
• ASSESS the Visual Acuity BEFORE DILATION of Pupil AND BEFORE Shining BRIGHT LIGHT into their eye
• TEST with a PINHOLE = DETECT a REFRACTIVE Error!

Question 5

How do you RECORD VA for DISTANCE Vision?

Answer 5

• If Px can ONLY read the 18m line, their DISTANT Vision is DEFECTIVE = 6/18
• If Px CANNOT READ the LARGEST Letter, they have to WALK TOWARDS
• If Px CANNOT READ the LARGEST, WHEN CLOSE to it, they have to COUNT the Ophthalmologist’s Finger held at 1m against a DARK BG - If Px can do this, VA = 1/60

Question 6

How do you RECORD VA for NEAR Vision?

Answer 6

• Ask px to WEAR READING GLASSES if they OWE them
• Test EACH eye SEPARATELY
• Px HOLDS NEAR Test Chart about 0.3m to read the SMALLEST print
• SMALLEST Print = N4 / N5
• LARGEST Print = N48