What is the perception of movement in the visual field? A number of you already know this aspect of vision very well and may have other ideas, opinions and experiences to share. Some of you may have an idea about it as part of the Bates Method, but not be sure what it implies, while others may be new to this whole concept. The aim is for each one of us, whatever level we may be, to reflect on the importance of the role this perception has in vision.
One of the basic principles of the Bates Method is relaxation, which in turn invites movement. It relieves the strain that creates fixation of the regard. Relaxation enables its movement which in turn generates more relaxation. The more there is movement, the more there is relaxation, the less there is strain.
So what is this movement that Dr. Bates insists on so much?
In numerous books about his method, the aspect of eye movement has been reduced to eye gymnastics, that is, looking right, left, up, down, rotating the eyes in one direction then in the other. Interestingly, there is no mention of this kind of eye gym in Dr. Bates' original book. It is but the interpretation that has emerged from other authors, of his emphasis on the importance of shifting the regard that is so natural to the normal eye. This interpretation of shifting as an eye gymnastics therefore, underlines the lack of understanding of Bates' principle of movement in vision.
Indeed there are two aspects of Bates' principle of movement.
The first aspect of movement in vision is the mechanical ocular movement shifting from one point of interest to another. It is the normal movement of the eyes, going constantly from one point of interest to another point of interest, tracing around the object regarded in order to send precise information about it to the seat of vision in the visual cortex. It is the brain that assembles this detailed information arriving from both eyes, analysing and interpreting it in order to provide us with a meaning of what is seen. Bates insisted that perfect sight is impossible without this constant shifting and, when it is not done unconsciously, students of the Bates Method are encouraged to do it consciously.
But why does the eye have to shift in order to see?
This natural shifting of the regard is the result of the physiology of the retina which requires, in order for it to obtain a sharp image, that the eyes be in constant movement in the form of fine saccades which enable the regeneration of the image. When the eye is artificially immobilised, as in a laboratory for example, the image on the retina disappears. The test that Bates invites people to do in order to experience the sensation of ocular immobility is to exaggerate this immobilisation by staring at an object without blinking or moving the eyes. After a few moments the eyes begin to burn or hurt and the object regarded becomes blurry.
The reason for this shifting is in the anatomy of the eye. Located in the centre of the retina in the axis of the pupil, is a tiny area called the "macula lutea" which contains only the photoreceptive cells (approx. 6 - 8 million), the cones, sensitive to colour and a high resolution of light. At its centre is the "fovea centralis" where the light rays should reach, in the normal eye. It is this tiny area, the only area of the retina, that provides us with sharp vision for details. However, the shifting with little saccades around the object regarded enables the foveas to see each part of the object sharply and transmit the sharp images of different parts of the object to the brain. The latter then combines the information received from both eyes, analyses the numerous sharp images received, interprets and identifies the object.
The remaining 110 to 125 million photoreceptive cells - in fact the large majority - called rods are in the rest of the retina providing us with a large field of peripheral vision. They are sensitive to black and white, contrast, low resolution of light and also to movement - providing us with night vision. The rods and cones interact in synergy. These two systems, central and peripheral vision, make it possible for us to see details sharply with the foveas while the context of these details is provided by the peripheral vision which is everywhere / everything in the visual field where we are NOT looking but nevertheless perceive.
This natural movement of the eyes also involves the extrinsic eye muscles which enable the eyes to look in different directions - left, right, up and down, near and far.
However, the eyes are directed by the brain. They are windows for the brain to access information from the exterior environment initially for survival purposes and are subject to the interest the brain has in its environment. When the brain has received a stimulus of interest, or threat, it directs the eyes to seek out the source of interest or threat in order to see it clearly and react accordingly. We are therefore, constantly scanning, searching, comparing, pursuing and exploring the environment with our eyes which never settle on a point for longer than a fraction of a second. When we are aware of what we are seeing, the mind is present in receiving the information, interpreting and analysing it.
If however the mind is occupied by thoughts, worries, memories, plans, day-dreaming or negative emotions, the brain is unable to give full attention to the integration of the visual information arriving from the eyes whose natural movement immobilises.
Dr. Bates called this immobilisation of the regard "staring" caused by strain of the mind, that is, the mind that is preoccupied with thoughts and therefore not present. Surprising though it may seem, the brain cannot simultaneously be aware of its surroundings and be lost in thought.
The other aspect of movement dear to Dr. Bates is the perception of movement of the surrounding environment which he called the swinging or pulsating of objects. This seems to have been of less interest to many authors on the Bates Method.
In Wikipedia, optical flow is defined as "a concept which approximates the motion of objects within a visual representation".
Two very important functions of normal vision are considered by Dr. Bates: the constant, relaxed shifting of the regard from one point of interest to another and the harmony between central and peripheral vision that induces the perception of the surroundings moving, swinging or pulsating in the opposite direction to the regard.
Although this perception may seem obvious to many, generally with good vision, it may be difficult for others. The mind has a knack of interfering with this perception through reasoning and intellectualising that "the trees are not moving, it's me that's moving!" which is indeed a reality. However, the perceptual and sensorial reality is that one has the feeling and impression that the trees, buildings etc. are indeed moving past and that feeling is real as well as logical. When the regard is moving and there is peripheral awareness, objects are constantly exiting and entering the visual field giving the impression that it is the world that is moving by, in the opposite direction to the regard.
We experience this perception when walking, running, swimming, driving, riding, cycling, jumping on a trampoline, swinging on a swing, lying in a hammock, rocking a baby or child, sweeping our gaze across the landscape and reading. Where there is movement of the regard and the body, there will be the illusion of movement in the peripheral field.
However, the world no longer moves:
- when the intellect overrides the sensorial experience.
- when there is strain as a result of the need to stabilise the world in order to feel secure.
- when there is no central fixation, or peripheral awareness, both fundamental principles of the Bates Method.
- in the case of emotional trauma. One of the many physiological changes in the body when under stress is the shrinking of the visual field, the dilation of the pupils and the fixed regard. Without peripheral awareness and the shifting there is no peripheral motion.
Dr. Bates is not the only one to underline the importance of the perception of peripheral motion. There has, since his time, been much published on visual perception, peripheral motion and optical flow. It is available in the literature and on the internet. Alain Berthoz, of the research institute in Paris, Collège de France, and Director of the Laboratoire de la Perception et de l'Action (research in perception and movement) wrote in his book "Le Sens du Mouvement" - when a subject moves in the real world, the image of his environment is projected in movement onto the retina and deforms in a very complex way. It is this deformation of the image on the retina while in movement that is called the "optical flow". In the case of lateral movement of the regard, as when we look out of the window of a train, the "optical flow" has a subtle complexity since nearest to the train the visual world appears to move in the opposite direction to the movement of the train whereas the landscape further away appears to move in the same direction. (Berthoz P. 68)
It is interesting that when people blind from birth have recovered vision through surgical operations, may panic when walking down the street having the illusion that the trees or buildings are coming towards them. What is so natural to many of us, even with lowered vision, can be terrifying when experienced suddenly.
Interestingly, this optic flow well known in the Bates Method also has repercussions on posture. Indeed the link between vision and posture is being increasingly explored by Bates Method and Alexander Technique teachers. However, many researchers have also studied this connection, a couple of whom are:
W. N. J. C. van ASTEN were interested in "how visual information of a scene, moving along the line of sight of a subject, affects postural readjustments made by a subject when instructed to maintain an upright posture".
W. H. WARREN and K. J. KURTZ studied "the role that central and peripheral vision play in the perception of the direction of translational self-motion, or heading, from optical flow."
Th. BRANDT, J. DICHGANS and E. KOENIG observed that "optokinetic stimuli allow for two perceptual interpretations. The observer may perceive himself as being stationary in a moving surround (egocentric motion perception) or he may experience an illusion of self-motion, so that the actually moving surroundings appear to be stable (exocentric motion perception)".
The perception of peripheral movement requires relaxation, presence and integration of the central and peripheral vision systems. In normal vision, this motion is logical and obvious. Where vision has lowered, this perception of optic flow is very often neither perceived nor understood and is an indication of the person's visual functioning. It is also a parameter of vision that is difficult to measure. However it can be felt. It can produce sensations both comfortable and uncomfortable and is directly connected to a person's mental strain. How many ophthalmologists or other eye care professionals take an interest in a patient's awareness of peripheral motion as a measure of good vision? Dr. Bates' observations seemed to be ahead of his time as is confirmed by the interest taken in this aspect of vision by later researchers. Let the landscape flow past, the objects swing and pulsate, the eyes relax and the vision will improve! The workshop following this presentation will be an exploration into what this peripheral movement feels like.
BATES, W.H. Dr., The Cure of Imperfect Sight by Treatment without Glasses, Central Fixation Publishing Co. N.Y., 1920
BATES, W.H. Dr., Better Eyesight Magazines, Novembre 1923,
BERTHOZ, Alain, Le Sens du Mouvement, Editions Odile Jacob, 1997
VAN ASTEN ,W. N. J. C., GIELEN, C. C. A. M. and DENIER VAN DER GON, J. J., Experimental Brain Research, Vol. 73, nº 2, November 1988, Springer Berlin,
BRANDT, Th., DICHGANS, J. and KOENIG, E., Experimental Brain Research, Vol.16, nº 5, Springer Verlag, March 1973
WARREN, W. H. and KURTZ K. J., The role of central and peripheral vision in perceiving the direction of self-motion, Perception & Psychophysics, 1992, vol.51, nº 5, pp. 443-454