Visual acuity refers to the ability to see details clearly and resolve separate objects. It has four main components: minimum visible, minimum separable, minimum cognizable, and minimum discriminable. Visual acuity is clinically measured using standardized charts at set distances and lighting conditions. Factors like illumination, contrast, pupil size, ocular health, and refractive error can affect visual acuity measurements. There are different types of visual acuity tests for distance and near vision. Common charts used include Snellen, Bailey-Lovie, Landolt C, and Jaeger charts. Special tests are also used to assess visual acuity in children.

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