As part of a proper Schoolvision assessment, there are 8 tests necessary to complete the child’s eye examination. With thanks to Geraint Griffiths, the founder of the schoolvision technique, in this series of blogs we will describe each test separately through series of questions and answers.
Here is a list of the eight tests:
- Brock string
- Dynamic fixation
- Accommodation facility
- Measuring Muscle Balance
- Trial Frame Challenges
- Follow – up
Here are the questions and answers on the Dyanmic Fixaton test.
Q: What is the purpose of doing this test on a patient who you already know is having reading difficulties and you know has a slow reading speed? I can see the benefit in doing this if screening a number of children- the results will certainly give confirmation of those who have a slower eye speed and have difficulty tracking and it may explain why some children cannot concentrate easily, but if you already know these things, are there additional benefits in carrying out this test?
A: This test is all revealing, it takes longer than the other tests and becomes a centerpiece of the screening.
Its original intention was to measure eye speed, but as you become familiar with it you can differentiate between children who have innately fast eyes but are inhibited by muscle balance problems and those who have slower eyes and muscle balance problems. Typically they both start slowly on set 4 but those with the fast eyes accelerate more quickly in sets 5 and 6.
It gives a strong indication of intelligence and the ability to learn. For instance when the initial practice sets are painfully slow and then quite rapidly improve albeit with inaccuracies.
By looking at the way the eyes move when the test is done it will tell you how well the patient can adapt to difficulties; for instance limiting the need for eye movement by using their peripheral vision.
Dynamic Fixation is more relevant to distance coordination problems than the simple CReST test. It gives a better indication of the possibility of secondary dyspraxia for example. The eye tracking movements on the DFT are much more extreme than the CReST and more severe than the standardised Schoolvision tracking test. It gives you feel for the real difficulties the child is having to overcome.
It is quite easy to say when time is pressing “I know enough now to prescribe reading glasses, but binocular vision problems affect all aspects of life.
Dynamic fixation can give a profound insight into the prognosis for the child depending on native wit and the severity of the binocular deficiency. It will give you a useful guide to the treatment plan and the potential for improvement.
My own feeling now is that this test is an essential part of the screening battery even if you don’t consistently uses it as a measure of improvement.
Q: Would you expect to see improvements in these results from one eye exam to the next?
A: Yes - this would make a good project
Q: Should we record an average of the 3 readings taken, or take the last reading as the most important one?
A: I think now that every phase of the test is important and the one at which you decide to stop the test is again in itself a measure. The 6 timed phases after explaining how to hold the chart and read the numbers are:
- Reading round once “And finish on the 1”
- Reading round three times “Starting and finishing with the 1”
- Another set of three circuits
- 4, 5 and 6 The final 3 sets of 3 recording the time after each set.
The most significant time is number 6, If you get this far the relationship between the times for 4,5 and 6 will help you to differentiate between different muscle speeds different athletic predispositions and dyslexia related tracking problems
It’s possible that the least meaningful measure is an average of the last three times. Every one of the 6 times has it’s own significance