If the person has horizontal nystagmus, the pictures are best presented vertically. The visibility of facial features can be tested also in older children by using the Hiding Heidi test. Then it is more fun to ask the child point to Heidi when she becomes visible. One of the two persons testing takes the picture of Heidi, the other tester takes the blank card. Whenever contrast sensitivity has decreased, it is advisable to measure visibility of facial features at different distances.
Surprises are common.
However, it is important not to force children to function at their threshold. If the function of a healthy child at the same luminance level is demonstrated, the teachers and therapists will better understand the requirements of the visually impaired child's communication.