Visual acuity

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)

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

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

8. 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.

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

10. Procedure

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

12. Near acuity chart Reduced snellen chart. N chart. M chart. Jaeger chart.

13. 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 )

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