visual acuity

information about visual acuity and its testing

1. Visual acuity and its testing

2. Visual acuity Visual acuity is the measure of spatial resolution Of the eye or,in other words an estimation of its ability to discriminate between two separate points.

3. Principle The two distinct points is only be recognized as separate When they subtend an angle of 1minute of arc At nodal point of the eye

4. Why needed To test visual function Refractive status of the eye Criteria for Person fitness to drive Elligiblity for entrance in profession

5. Measurement of visual acuity in infants.

6. OKN (optokinetic Nystagmus test ) Commonly used test on neonates Test object moves in one direction. Based on observation of perpendicular eye Movement In this test nystagmus is elicted By passing A succession of black n white stripes of okn drum

7. Prefrential looking test

8. Catford drum test

9. Visual evoke response (VER)

10. Teller chart

11. Assesment of visual acuity of 1 to 3 years

12. Cardiff test cards

13. Worth ivory Ball test

14. Marble game test Place marble in the hole of the box Intended to monocular visual function Vision is notef as usefull or less usefull

15. Assesement of visual acuity in preschool children(3-5 yrs)

16. Landolt c chart

17. Broken wheel test Cards are presented With picture of cars, very familiar to the child Two cards are held before the child,he simply has to recognize which one is broken. It consist of 8 pairs of test cards and a sample pair of card

18. Illitrate E chart

19. Allen card

20. Assement of visual acuity above 5 years

21. Key points

22. Snellen visual acuity chart

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25. Disadvantages of snellen chart

26. Logmar chart It is logarithm of minimum angle of resolution. It consist og 5 letters in each line Based of minimum angle of resolution Have regular progression in the size and spacing Of letter from one line to next

27. Continue Each letter has score value of 0.02 log units Since there are 5 letters Per line The total score For a line On the Logmar chart represents a change of 0.1 log units . Logmar VA =0.1 +value Of best line read – 0.02 ×(number of optotypes read)

28. Near vision charts

29. Jaeger chart

30. Snellen’s near chart