Eye-Tracking problems and their implications

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 shortsightedness, 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.

Eye-Tracking Introduction

What are the symptoms of an eye-tracking problem?
  1. Needing to run a finger underneath the line when reading.
  2. Reading the same line again or skipping lines.
  3. Losing “concentration” after a short time while reading a book.
  4. Guessing the letters at the end of words.
  5. Having tired eyes.
  6. The words appearing to be blurred.
  7. The words seeming to float around.
  8. Needing to rub the eyes after reading for a period of time.
  9. Difficulty copying words from the black/white board.
  10. Needing to close one eye when reading (Voluntary Occlusion).
  11. Feeling slightly queasy when reading for a period of time.
These are all signs of a student who has an eye-tracking difficulty. A student may have one or two of the above signs but is most unlikely to have them all.

Visual Chunk Size Explained

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! (See Chapter 11 for a more detailed discussion on how we judge distance.)

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.

We refer to the size of a word, i.e. the numbers of letters it contains, as the “chunk size”. As children get older and read longer words then we say that the chunk size is increasing. When we choose reading material for a child of a certain age we consider two things. First, we consider the degree of comprehension required to follow the story and second, the vocabulary, in particular the length of the words. How often have we said “that is a very big word for someone your age to know”?

If a child has difficulty, understanding material, which is apparently age appropriate, it may be that he has a small chunk size rather than that he has a problem with comprehension. Very often these children have a very wide spoken vocabulary and yet seem to have difficulty reading books considered suitable for their age.


Take a piece of paper and cut a hole in it that is wide enough to hold only five letters and read the preceding paragraph. Your degree of comprehension will be greatly reduced but, more importantly, you will understand how someone with a small chunk size reads.

Why does my child read some words backwards e.g. "no" for "on", "was" for "saw"

We all have a dominant hand and foot i.e. most people are right-handed and right-footed although some people are left-handed and/or left-footed. Some people are considered to be ambidextrous because they are very skilful with both hands but, even so, one of the hands will be dominant.

In the same way, we all have a dominant or preferred “direction of processing” although the degree of dominance varies from person to person. When walking through a forest, most people who are right-handed will tend to brush the branches aside sweeping their right hand from left to right. (vice versa for people who are left-handed). However, not all right-handed people will have a dominant direction of processing from left to right (vice versa for left-handed people).

In ancient Greece words were written along a line from left to right and the subsequent line was written right to left and so on in a zigzag fashion. Most languages nowadays, apart from in the Middle East, are written from left to right. Most people prefer to process from left to right but people who naturally process from right to left will seemingly read words backwards i.e. will read “was” for “saw” etc. This occurs only for words that can be read backwards. Some people in education are of the opinion that this is where the term “backward children” came from.

Perceptual Difference

Why does my normally bright child find it difficult to remember which is left and which is right?

Parents are very often bewildered as to why their children continue to find it difficult to remember left and right. It is quite common for a young child to be confused between left and right and to use memory aids to help him remember. He may remember that he writes with his right hand and then simply decides if something is on the same side as the hand he writes with or not – he may remember that he kicks a football with his right foot or wears his watch on his left wrist. This is quite normal but what is not quite so normal is the continued use of such aids over a period of years.

Children with dyslexia are often confused between left and right and many of them will continue to use a memory aid. The problem is not the inability to remember the label of left and right but the inability to sense the left hand side and the right hand side. In other words the vertical midline is not well defined in their personal space and we call this “horizontal or lateral confusion”. It is very difficult to label something that you are unaware of and much more difficult to remember that label!


Stand in the middle of a room and decide whether the door is on your left hand side or your right hand side. Close your eyes and turn round slowly several times in a clockwise direction and then several times in an anti-clockwise direction. Without opening your eyes decide if the door is on your left hand side or your right hand side. Now you will understand what is like to be confused by sidedness!

The reason that this confusion arises is that you have lost your sense of the relationship between your vertical midline and the room around you. People who are confused between left and right are often unaware of the relationship between their midline and their surroundings. If a student has this problem, it is paramount that it is addressed soon as possible.

Why does my child often read the same line again or skip lines when he is reading?
A child who has a preference for right to left processing may find that he tends to read the same line twice. He may also tend to skip lines by consciously trying to avoid reading the same line twice, by consciously casting his eyes on the line below. However he may cast his eyes downward too much and actually read the line two lines below. If the reader is a mechanical reader he may be totally unaware of what he has done. There are other reasons why a child may skip lines when reading and one of which may be that he has “vertical confusion” which is explained below.
Why does my child oftern "lose his place" when he is reading?

When reading a book, some people have great difficulty finding their place again if they are distracted and look away from the book for a short while. This is noticeable as the child’s head may be seen to give a slight wobble as they seek the spot on the page to continue reading. They may put their finger on the last word they have read to keep their place. Without such a strategy they may return to the beginning of the page or paragraph that they have been reading. Such people suffer from “vertical confusion”.

Vertical confusion

In the same way that some people are confused between left and right (horizontal or lateral confusion) they may also be confused between up and down, above and below (vertical confusion). As well as a vertical midline we also have a horizontal midline running horizontally through our eyes. Some people do not have a well-defined sense of this horizontal midline in relation to their surroundings. Consequently, they will have difficulty in perceiving whether something is up or down, above or below the line of their eyes. It is easy to appreciate how this can lead to a child skipping lines when reading or not being able to fine their place again when distracted from reading a book.


Stand in a room and look at a shelf with objects sitting on it so that the shelf is level with your eyes. Look at an object on the left hand side and another object on the right hand side of the shelf and decide whether the objects are “above” or “below”. Next tilt your head at an angle of about 45 degrees to the right hand side. Now decide if the object on the right hand side of the shelf is above or below. Next decide if the object on the left hand side of the shelf is above or below. Carry out exactly the same procedure only this time tilt your head to the left hand side. Decide if there is the same degree of confusion tilting your head either way.

For most people there will be a slight perceptual difference in the degree of confusion as the dominant eye should be the eye that calibrates “above” and “below”.

Why does my child have difficulty copying a list of words accurately from the blackboard into his exercise book?

Children who experience vertical confusion will find it more difficult to copy a list of words from the blackboard into his exercise book. Imagine a child taking down the following list of words:

  • dog
  • cat
  • camel
  • elephant
  • tiger
  • hippopotamus

The child may write the first two words accurately but then write “camel” as “catel”, “elephant” as “elemhant” or “tiger” as “tiher”. This causes great confusion for parents and teachers, as they cannot understand where the student discovered the “t” sound in camel, the “m” sound in elephant or the “h” sound in tiger.

You can imagine that if you had a rifle with a telescopic sight then it would be a relatively easy task to line up the cross wires on the target and shoot accurately. However, if you were told that the horizontal cross wire was slightly wrong, and you observed that the rifle always shot above the target, you would compensate by putting the horizontal cross wire slightly below the target before firing. You would have a major problem trying to hit the target if, each time you were to take aim, the horizontal cross wire changed position. This is what happens to someone who has vertical confusion. This is why, when they copy down the words, they place inappropriate letters from the words above or below into the word they are writing.

In the above case the child has taken the “t” from “cat” and put it into “camel” and the “m” from the word “camel” and placed it in the middle of “elephant”. Similarly the “h” from “elephant” has been put into “tiger”. The reason why the child cannot recognise that the “t” is a totally inappropriate sound for “camel” is dealt with in Chapter 4 dealing with the phonetic strategy for spelling and auditory sequencing.

Many children find a solution for vertical confusion by copying down the first one or two words then looking down at the words they have written, (in this case “cat”) and looking for it on the blackboard and then copying down the word below it, (in this case “camel”) and so on. This is an aid, but it is not a solution to the problem for two reasons. Firstly, this solution is very time-consuming and the child will take longer to take the material down from the board. As a result the child will feel very conscious of being “slower” than the rest of the class. Secondly, to overcome this feeling of failure, the child will tend to rush when writing down the list and will become careless, which also has negative results.

The solution to the problems caused by confusion between left and right (horizontal confusion) and between up and down (vertical confusion) is to develop in the student a well-defined sense of his vertical midline and his horizontal midline in relation to his surroundings. This is a contributory method by which eye-tracking problems suffered by so many students with dyslexia may be dealt with.

What does it feel like to have an eye-tracking problem when reading?

There are many different types of eye-tracking problems but to experience what it is like to read with an eye-tracking problem carry out the following demonstration.


Take an ordinary paperback book and start reading it as normal. After the first paragraph, move the book from side to side slowly, about an inch at a time, and continue reading for two or three paragraphs keeping the movement going. That is what it feels like if you have horizontal confusion.

Next, continue reading without moving the book for one paragraph and then start to move the book up and down slowly, about an inch at a time, and read for a further two or three paragraphs. This is what it is like to have vertical confusion.

Finally, read a paragraph normally and then, this time, move the book from side to side and up and down. Keep alternating these movements for the next three paragraphs. This is what it feels like to have horizontal and vertical confusion.

It is not easy to read for a long period of time without experiencing eyestrain if you have an eye-tracking problem. In severe cases the child may feel queasy in the tummy and complain that he feels “sick” when reading.

If you look again at the list of signs of eye-tracking problems at the beginning of this chapter, you will now be much more aware of the reasons why such problems occur.

Why does my child lose concentration after reading for a period of time?

If you have carried out the above demonstration successfully, you will be able to sympathise with a child who has an eye-tracking problem. Moving the book from side to side, or up and down, or both does cause eyestrain. When a child is reading and suffering from such eyestrain, he will inevitably look up from the book and look around the room at distant objects to relieve the strain. A parent or teacher may interpret such behaviour as losing concentration, whereas in fact the child is merely relieving eyestrain.

In the next Chapter, you will discover how eye-tracking difficulties can affect the level of comprehension a child has when reading.