Visual acuity

1. UMESH BELBASE
Visual Acuity

2. Vision…………?

3.  Visual acuity is the spatial resolving capacity of
visual system or the ability to see two seperate
object as a separate.

4. Component of visual Acuity
 Minimum visible (Detectable)
 Minimum separable (Resolution)
 Minimum cognizable (Recognition)
 Minimum discriminable (Hyperacuity)

5. Clinical measurement of visual acuity
 Criteria
 Normal testing distance (distance visual
acuity) -6m
 For near – 33cm / 40 cm.
 Illuminated visual acuity chart.
 Proper room illumination.
 Steps
 Unaided VA (OD,OS,OU)
 Aided visual acuity (OD,OS,OU)
 Pinhole VA (OD,OS)

7. Factor affecting visual acuity
 Illumination of test object.
 Contrast of letters.
 Pupil Size.
 Ocular health.
 Refractive status.

8. Types of visual acuity
 Distance
 Near
 Single objects, numbers, words or letter versus
continuous text.
 Reading distance

9. Distance visual acuity
measurement and charts.
 Ideally , you should not use count finger.
- If you do use counts finger, note at what
distance.
- eg. cf@2m, cf@1m
• Hand motion.
• Light perception.

10. Distance visual acuity charts.
 Snellen visual acuity chart.-6m
 Bailey-lovie chart (logMar).-4m, 2m, 1m
 Landolt ring chart (C chart)
 Feinbloom distancechart.

11. Procedure

12. Formula
VA= Testing distance (6/6,6/60….)
Distance at which letter
substend 5 min. of arc.

13. Near acuity chart
 Reduced snellen chart.
 N chart.
 M chart.
 Jaeger chart.

14. Assessment in Childrens
 Forced choice preferential looking.
 Optokinetic nystagmus test.
 Catford drum test.
 Tumbling E test.
 Cardif acuity test. (0-1 years)
 Dot acuity test.
 Miniature toy test. (2-3 years )

15. Forced choice
preferential looking
Optokinetic nystagmus
test.
Cardif acuity test
Miniature toy
test