Understanding Eye Tracking – part 1
It is estimated that over 80% of information that is transmitted to the brain during academic learning is transmitted visually i.e. by use of our eyes. It is therefore essential for efficient and effective learning to take place that our eyes are functioning well. This goes beyond establishing that there are no refractive problems, such as short-sightedness, or pathological problems (disease), which would be identified in a standard eyesight test.
Reading is a complex visual task and requires good vision not just good eyesight. For example, both eyes have to work together as a team and converge equally in order to focus on the words being read which, incidentally, are generally about 16 inches from the eyes, not the 20 feet used in a standard eyesight test. The eyes have to be able to focus on more than a few letters at the same time to be able to read longer words easily. The eyes also have to be able to track across a page line-by-line and from left to right without skipping lines or reading lines twice. Difficulties associated with several different eye-tracking problems are discussed below.
What are the symptoms of an eye-tracking problem?
- Needing to run a finger underneath the line when reading.
- Reading the same line again or skipping lines.
- Losing concentration after a short time while reading a book.
- Guessing the letters at the end of words.
- Having tired eyes.
- The words appearing to be blurred.
- The words seeming to float around.
- Needing to rub the eyes after reading for a period of time.
- Difficulty copying words from the black/white board.
- Needing to close one eye when reading (Voluntary Occlusion).
- Feeling slightly queasy when reading for a period of time.
These are all signs of a person who has an eye-tracking difficulty. You may have one or two of the above signs but are most unlikely to have them all.
Catching a ball seems quite a simple task for most of us but we all know people who find it difficult. We say that they have little, or no, co-ordination. When you consider it, catching a ball it is very complex skill. Both eyes have to be working in a co-ordinated fashion so that they can judge the speed of the ball, by estimating the distance the ball is from you several times, over a very short period of time. The brain then has to send a signal through the arm muscles and hand muscles to work in co-ordination to catch the ball.
There are many muscles in the arms and more in the hands. If any one of those muscles in the arms or hands were damaged, or not working in co-ordination with the other muscles, then you would be unable to catch the ball. This does not even taken into consideration the very delicate muscles that control your eyes, which are the muscles used to estimate the distance that the ball is from you. Having considered the complexities involved in catching a ball it is really amazing that the human body can do it. We tend to take such a simple skill for granted.
Have somebody throw a ball to you three times from a distance of one, two and three metres. Repeat the three catches first with your right-eye closed and then with your left-eye closed. Your eyes need to be co-ordinated to measure the distance and, if you are only using one eye, you will not be able to measure distance accurately. Co-ordinated eyes are necessary to catch a ball!
In the same way, we tend to consider the skill of moving our eyes across lines of words on a page as a simple task. It is a natural skill for most people but not for everyone. Co-ordinated eyes are necessary to read!
Studies by Oxford University’s Physiology Department found “Patching one eye can improve eye control and reading in dyslexic children with poor eye control”. However this may solve the problem in the short term, as it removes the need for the eyes to be co-ordinated, but can be disadvantageous in the long term.
Why can my child read small words but have difficulty with longer words?
Each of our eyes has a field of vision and the area where the two fields of vision overlap is the where we see words when we are reading. In simplistic terms, if the overlap is small then we will be able to see only small words, whereas if it is large, we will be able to read large words.
Some people with reading difficulties may have a small area of overlap. These people are relatively content to read a passage, which contains only small words. However, when challenged to read a passage with longer words then one of the following occurs. They may just stop reading when they come across longer words. They will be confused and have little comprehension of what they are reading. The other possibility is that they will continue to read but will guess the ends of words e.g. the following words all begin with th:, those, there, their, through.
The following sentence
The man bought those apples could be read in the following different ways:
The man bought there apples. The man bought their apples. The man bought through apples.
The first two sentences cause confusion, whereas the third sentence does not make any sense at all.