I had worked in practice for over 25 years before a colleague recommended buying the Cardiff Acuity Test. I admit that I was slightly sceptical at first, having no experience of how effective a preferential looking test would be on a toddler or how easy it would be for the optometrist to use.
Created by Dr Maggie Woodhouse, the test is designed especially for the harder-to-test patient age group, one to three years old, but I find that it is also suitable for older patients with a learning disability.
It comprises a series of picture cards. All pictures are the same size, but are drawn with decreasing width of outline bands onto a neutral grey background, either at the top or bottom of the card. If the picture is below the acuity limit for that child, it will be invisible.
The principle of the test is preferential looking, whereby the child looks to the part of the card with the picture on it rather than the plain stimulus. If the toddler can see the picture they will look towards it and the optometrist can judge the target’s position from the child’s eye movements.
It is important that the examiner doesn’t know in advance the position of the picture.
"I find the Cardiff Acuity Test to be an invaluable tool that allows me assess quickly and easily the acuity of each eye on very young children, and occasionally on adults with a learning disability also"
This is the bit that I was hesitant about before purchase as I wasn’t sure how easy it would be to observe and interpret the child’s eye movements, but it is actually very obvious where they are looking.
The test can be done at one metre or 50cm; I personally choose 50cm so that you are up close to the toddler and can see their eye movements easily. This can measure acuity to the equivalent of 6/7.5.
The toddler will sit on their parent’s knee, where they feel safe and comfortable, and wear monocularly occluding spectacles (bought separately), with the optometrist positioned directly in front of them.
I will begin by showing the largest picture at the eye level of the toddler, making a mental note of the direction that the toddler looks, before moving onto a second card and observing once more. If they have looked in the right direction both times, I will begin the process with the next set of cards.
I find the Cardiff Acuity Test to be an invaluable tool that allows me assess quickly and easily the acuity of each eye on very young children, and occasionally on adults with a learning disability also.
I don’t know how I managed without it for so long.