Refractive problems are very easy to detect because most of them are associated with decreased Visual Acuity and its associated symptoms: headaches, blinking, smarting eyes, etc.
This is a refractive error characterised by the eye using a point in front of the retina .
It is what is commonly referred to as “short-sightedness”.
When we prescribe negative lenses we manage to modify the focal point and situate it directly in the retina.
This refractive error is characterised by the eye using a point behind the retina to focus on the image of the object. Therefore, distant images appear slightly out of focus, with this being more pronounced in close-up vision.
This refractive error is characterised by the eye using a point behind the retina to focus on the image of the object. Therefore, distant images appear slightly out of focus, with this being more pronounced in close-up vision, etc.
This refractive error is characterised by the eye using a point behind the retina to focus on the image of the object. Therefore, distant images appear slightly out of focus, with this being more pronounced in close-up visionetc.
With astigmatism, the cornea is unevenly curved and different points of the retina are used when focusing on images.
Different conditions exist depending on the focal point used:
Myopic astigmatism: the first focal line is in front of the retina, while the second is on the retina.
Hypermetropic astigmatism: the first focal line is on the retina, while the second is behind the retina.
Presbyopia is a refractive condition, also known as “tired vision” that commonly appears after the age of 40 and is characterised by difficulties when focusing on images close up, when we are reading.
This difficultly can easily be corrected with positive lenses as these ensure images can be focused and kept in focus in close-up vision.
Strabismus is the condition in which one eye or, on an alternating basis, both eyes lose alignment and deviate.
Depending on this deviation we can identify:
- ENDOTROPIA: an inward deviation.
- EXOTROPIA: an outward deviation.
- HYPERTROPIA: an upward or downward deviation.
- CYCLOTROPIA: da combined condition involving both horizontal and vertical deviation.
The causes of strabismus are manifold and, before establishing a prognosis of the case and starting treatment, it is very important to find the origin of the deviation.
This might be:
- AnisometropIa: a significant refractive difference between one eye and the other.
- Binocular and Accommodative Problems.
- Brain Damage.
Amblyopia is a condition in which, despite the absence of pathology, one or both eyes present a Visual Acuity below 100% which is not compensated by optical lenses.
On a Behavioural level, we could say that amblyopia is a dysfunction in terms of gathering, processing, analysing and responding to visual information, meaning the Amblyopic Eye will have problems with:
- Oculomotor Motility.
- Spatial Localisation.
Amblyopia is usually associated with:
- Refractive Errors.
The Visual System act in unison by coordinating the eyes to see a single image (binocular system), focusing the image at the different distances (accommodative system) and moving the eyes for sustaining the stimulus in movement (visual pursuit), or for jumping from one fixation to another (visual saccade).
Visual Efficiency, therefore, will depend on the individual’s capacity to coordinate these systems and sustain them in time.
CWhen the overall system becomes unbalanced, problems arise in one or all of the subsystems. This is when we encounter:
- Oculomotor Problems
- Accommodative and Binocular Problems
Visual Development is very closely linked with Motor Development, especially regarding the Control of the Oculomotor Movements.
There are 3 types of oculomotor movement:
- Fixational: sustaining the visual fixation on a determined stimulus. Only when the eyes remain fixed upon a stimulus can we differentiate and determine what it is.
- Visual Pursuit: this is the oculomotor movement that enables us to maintain the fixation upon a moving stimulus. This is an incredibly important skill when practicing sports. For example, the visual tracking of a ball as we are running to reach it.
- Saccades: these are the oculomotor movements that enable the eyes to jump from one fixation to another. We make more brusque saccadic movements, such as those made by babies when they hear a sound, and other more subtle smoother ones such as the jumps of fixation we make when reading, writing or copying information.
SYMPTOMS: The symptoms of Oculomotor Problems include:
- Sustained attention requires a great deal of cognitive effort.
- Difficulty/inability maintaining attention.
- Constant loss of attention.
- Losing one’s place when reading.
- Omitting or skipping words when reading.
- Transposition of letter or words.
- Inventing words.
- Difficulty copying from the blackboard.
- Following text with a finger for guidance.
- Reading comprehension problems.
- Motion sickness.
- Car sickness.
- Feeling faint when performing sporting activities.
- Poor motor skills in general and in hand-eye coordination.
Accommodation is the skill of focusing the eyes rapidly and automatically regardless of the distance between the subject and the workface.
Accommodation is closely related with the ability to direct and maintain attention.
- Accommodative Posture:
- Accommodative Insufficiency: the accommodative plane is situated behind the stimulus presented.
- Accommodative Excess: the accommodative plane is situated in front of the stimulus presented
- Accommodative Inflexibility: difficulty when rapidly changing focus from near to far and vice versa.
- The subject performs activities to close up.
- Occasional or sustained blurred vision when working close-up or when making rapid changes from near to far or vice versa.
- Red or tired eyes after working.
- Headaches when reading or writing.
- Excessive blinking.
- Visual fatigue and/or abandonment of the task.
- Sustained attention deficit problems.
The visual system is designed in such a way that the extraocular muscles work together with a high degree of precision, thereby ensuring we obtain a single image just as though the two eyes were one.
This skill is closely linked to the Accommodative System and to Oculomotor Control.
- Binocular Posture
- Convergence Excess: the binocular plane is situated in front of the true image.
- Convergence Insufficiency: the binocular plane is situated behind the true image.
- Binocular Inflexibility: difficulty with rapidly changing the binocular plane when going from near to far or vice versa.
- Strabismus: loss of binocularity with a real deviation of one eye or both eyes inwards, outwards, upwards or downwards.
- Diplopia: the inability to merge the two images into one.
- Reduced Stereopsis: the ability to perceive images in three dimensions (stereopsis) is reduced when there are binocular dysfunctions.
- Unusual bodily postures.
- Performs activities too close up.
- Turns head to prevent diplopia.
- Closes or covers one eye.
- Diplopia occasionally apparent.
- Rubs eyes frequently.
- Has problems with sustained concentration when reading, copying information, doing homework, etc.
- Has poor reading comprehension.
CEvery second our sensory organs send 10 billion bits of information to our brains. Of these, only 100 bits reach the highest levels of our cerebral cortex (prefrontal lobe). This ability to select or filter information is what we call “ATTENTION”.
We tend to define attention-related problems as “Attention Deficit” and this can lead us to mistakenly believe that everybody with attention deficit problems finds it difficult to pay attention. A distinction should be made between:
- Attention deficit or finding it difficult to pay attention. In this case, normally, the problem is the entry of the sensory information, be it visual, oral, tactile, proprioceptive, etc./li>
- Short attention span problems: the inability to pay attention for sustained periods of time.
- Divided Attention Problems: the inability to pay attention to one task at the same time as performing another. For example, listening to and absorbing what the teacher is saying, while copying information from the blackboard.
- Peripheral or Ambient Interferences: problems deciding where to pay attention. This is a problem with filtering the appropriate stimulus.
Bearing in mind that 80% of the sensory information we process pertains to the Visual System, any interference to our vision can lead to attention deficit problems.
It is important to perform a Visual Performance Examination in order to evaluate whether the Attention Deficit Problems are Vision-related or not.
Visual problems that can lead to the development of attention deficit problems:
- Oculomotor Problems.
- Accommodative Problems.
- Binocular Problems.
- Visual Information Processing Problems.
Learning can be defined as the stereotypical responses of the individual to determined stimuli and/or certain situations.
The terms: Learning, Development, Performance, Behaviours are related.
Human beings do a lot of learning:
- Motor Learning: gravitational learning.
- Visual Learning.
- Learning to Speak.
- Learning to Read.
- Learning to Write.
- Learning to Think.
A learning problem is a general term that describes specific learning problems.
When most professionals talk of learning problems they are referring to Higher Level learning problems such as Reading, Writing, Mathematics, Cognitive Processes, etc., but human beings continue developing and progressing in Learning Levels. This makes it difficult for them to reach an optimum Cognitive Learning Level (development of logic) unless they have undergone an optimum Motor Learning, because firstly a solid structure must be established in a hierarchical order that enables them to grow in a stable and confident manner.
We learn everything in accordance with the following pattern:
We need to evaluate:
- The ENTRY OF THE SENSORY INFORMATIONL. Any difficultly in the Sensory Systems (Touch, Proprioception, Hearing, and Vision) means that the information registered by the different Processing Levels does not arrive correctly and, therefore, the output of the information will be inadequate.
- INFORMATION PROCESSING LEVEL. There are different information processing levels, with these depending on the Development of the person. In many cases we are confronted with barriers that make the processing level lower than that expected for the chronological age of the patient. It is necessary to evaluate the Processing Level, significant differences between Sequential Processing (Left Hemisphere) and Global Processing (Right Hemisphere), in order to establish the level of functioning and the suitable therapies for resolving this situatio.
- MOTOR RESPONSE. Behaviour, performance, an individual’s response to a given stimulus. It depends on the other two areas. These are the motor responses that indicate the learning problems:
- Eye-Hand Coordination.
- Patterns of Movement.
- Oral and Written Expression.
We must not forget that this level is completely linked with and influenced by the two previous ones. This means that if all we do is provide therapies for resolving information output difficulties and forget to evaluate and treat the information input and processing areas, we will not be solving the problem. In many cases the maximum we achieve, after hours and hours of writing and reading exercises, doing schemes of work and summaries, is to provide patients with strategies for resolving the current situation without creating the FRAMEWORK that helps them to take their development forward.
Vision is the last sensory system to develop. It depends on the rest of the sensory systems and once it has reached its maximum potential (approximately at 8 years old), it begins to take over from the others.
Children use their Vision to determine colours, shapes, thicknesses, textures, spatial limits, speeds, rhythms, visualise words, sounds, images, concepts, project themselves in space and time.
Everything children see, how they interpret it and the speed and skill of visual recognition determine the majority of the response activities.
Therefore, when we have:
- Abnormal body postures, especially when we are resting or immobile.
- Eye-Hand Coordination Problems, not only in gross motor activities (bodily coordination, sports, etc.), but also in the discriminative ones (drawing, cutting out, etc.).
- Reading Problems.
- Writing Problems.
- Difficulties with mathematics both in calculus activities and in mathematical thought.
- Logical-deductive development.
- Expression and organisation of information on both an oral and written level.
We must consider whether the child has:
- Suitable Neurophysiological Structure.
- Integral Sensory Systems, especially the Visual Systeml.
- A well-developed Information Processing Level.
- Appropriate Motor Responses.
The evaluation of these levels enables us to find the barriers and difficulties and to act in a more secure manner to resolve the child’s learning problem.