Dynamic Visual Acuity (DVA)

Explained in simple words

1DVA stands for Dynamic Visual Acuity. In simple words, it tests how clearly you can see while your head is moving.

2Many patients say something like this — "Doctor, when I sit still I can see well, but when I walk, the board or the road looks shaky or blurred."

3This happens because of a reflex between the ear and the eye. When the head moves, this reflex moves the eyes by exactly the same amount in the opposite direction.

4That is what keeps the picture steady on the eye, just like image stabilisation in a camera or a mobile phone.

5If the balance organ is weak, this reflex fails. The eyes cannot keep up with the head, and the picture slips and becomes blurred while moving.

6The DVA test measures exactly how much vision is lost when the head moves. This is something an ordinary eye test cannot show.

7The test is done in two simple steps and does not hurt at all.

8First, you are asked to read letters or symbols on a chart while sitting still, with your head steady. This gives your normal vision reading.

9Those who cannot read letters are shown simple pictures, or the letter "E" pointing in different directions, and are only asked to say or show which way it points.

10So the test can be done easily even by people who have never been to school.

11In the second step, the same chart is read while the head is gently moved from side to side, or up and down, about twice a second.

12The doctor may move your head for you, or a small sensor placed on the head guides the speed, so that the movement is even.

13The movement is small and slow enough to be comfortable. There is no jerking of the neck.

14The computer or the doctor notes how many lines of the chart you can no longer read while the head is moving.

15In a healthy person, vision drops by only about one line, or not at all.

16If vision drops by three lines or more, it shows that the balance organ on one or both sides is not supporting the eyes properly.

17This explains why such patients feel unsteady in crowded markets, while walking on uneven roads, or while travelling in a bus.

18It also explains why some people are afraid to walk outside even though their eye check-up was reported normal.

19The test is completely safe. There is no radiation, no injection, no medicine and no side effect.

20It takes only ten to fifteen minutes. Please bring your spectacles if you use them for distance, as the test is done with your usual glasses on.

21Tell the doctor if you have severe neck pain or a recent neck injury, so the head movement can be adjusted or the test avoided.

22This test is also excellent for measuring recovery. After a few weeks of balance exercises, we repeat it and you can see the number of readable lines improve.

23That improvement is proof that the exercises are working, and it tells us when you can safely return to driving, work and daily activities.