Testing V.A in verbal children Allen picture card (Kay pictures). HOTV test (Sonsken- Silver test). Sheridan- Gardner test. Landolt rings (C). Familiar tumbling E test.

Allen picture card (Kay pictures). Near test cards are easier for younger children. Disadvantages: Pictures are not constructed according to snellen form (each element in the target subtends 1 of visual angle) Some pictures are not familiar to the child e.g. telephone. Pictures are variably larger than the corresponding Snellen letter target. Smallest one 20/30=6/9. But most children respond to this test.

Allen picture cards (Kay pictures)

HOTV test (Sonsken-Sliver test) Require pattern recognition and matching of progressively smaller optotypes with those on a hand-held card. These letters are chosen to be of average recognition difficulty, and have a vertical axis of symmetry. Advantages: More accurate in amblyopia (crowding phenomenon) Match one optotype with multiple optotypes. Exact correspondence to graded snellen optotype.

Sheridan-Gardner test. Require children to match familiar object pattern viewed at distance with those on a near card.

Which is better??? The main deference between the Sheridan-Gardner test and the HOTV test is that there is no crowding phenomena in the Sheridan-Gardner test, because it show a single optotype in each card , so it is not accurate to test an amblyopic child with the Sheridan-Gardner. Because the crowding phenomena is the hallmark to the presence of amblyopia , so it is very important to use these two tests in the correct way and on the suitable patients in the HOTV test.

Landolt rings (C) The child points to a similar ring on a hand-held card. Some children are confused. Can be used in illiterate adults; it does have the advantages of corresponding directly to the Snellen chart.

Familiar tumbling E test Requires matching orientation of the letter E with a figure or the child's fingers, Its major advantage is the direct correspondence to graded Snellen optotypes.

Important notes: In some cases, the patient may have a latent nystagmus, which appears when the other eye is occluded. The latent nystagmus reduces the V.A due to the inability to fixate the target. In these cases when testing V.A, we must occlude the eye in a way that’s prevent the latent nystagmus to occur. There are methods to perform that: Using a +5.00 D in front of the eye, it will reduce the vision in a marked limit and in the same time it will not produce nystagmus. It is an important exception that the patient does not be hypermetropic.

2. By putting the occluder in front of the eye at a distance nearly 10 cm, in this way we occluded the eye and prevent the nystagmus. 3. By using the frosted lens, which present in some trial cases. This lens permits some light to enter the eye but it also occlude the eye from seeing anything and so no nystagmus will occur.