Catalan Association of Optometry and Vision Therapy

Visual problems

Visual problems that affect poor visual efficiency are:

- Refractive errors: visual problems are easier to detect. They alter the normal visual acuity (VA) due to structural factors of the eye (axial length, corneal curvature) or aging of the lens. Are classified as:

- Myopia
• It looks at blur distance vision because the image is formed in front of the retina.

• When prescribing negative lenses, we modify the focal point and place it directly on the retina.

• Their appearance depends not only on environmental factors but also hereditary.

•It is associated primarily to increased axial length of the eye or also a high power optical system of the eye.

- Hyperopia
• Leads to major difficulties in near vision focus because if the lens doesn’t compensate, the image will be formed behind the retina.

• Farsighted people can make an accommodative effort to see clearly but gives rise to visual stress symptoms such as headache, general tiredness, blurring over time. This decreases the efficiency in near vision tasks.

• When we prescribe positive lenses the focus point is placed directly on the retina.

• Hyperopia is associated primarily with a short axial length of the eye or a low-power optical system of the eye.

- Astigmatism
• It affects vision at distance and near.

• It compensates with toric lenses.

• May be associated with myopia or hyperopia.

• Usually caused by a cornea with the two principal radii of curvature and orientation determines the axis of astigmatism.

- Presbyopia
• Assumes blurring in near vision due to aging the muscles surrounding the lens.

• Usually starts to occur between 40 and 45.

• It can be compensated by prescribing positive lenses with bifocal or multifocal lenses (also called progressive).

-Binocular Coordination disorder: For there to be good binocularity (both eyes working together), the images that reach the brain must be as close as possible to merge and perceive them as a single image. The fact that the images have a difference in perception allows for three- dimensional vision (3D or stereopsis). Changes of binocularity are classified as:

- Disorder of binocular vision
- Basic exophoria is a latent deviation of the visual axis outward in the same proportion of both near and far. Symptoms: diplopia or suppression of one eye, headache, drowsiness, poor concentration.

- Basic esophoria: a latent deviation of the visual axis inward in the same proportion of both near and far. Symptoms: diplopia, headache, drowsiness, poor concentration, and blurred vision.

- Convergence insufficiency: Difficulty in converging the eyes or maintaining alignment of the eyes at close distance. It is easy to show fatigue and even can cause double vision (diplopia). It may be associated with accommodative excess.

- Convergence-Excess: Difficulty in relaxing eye convergence following prolonged near tasks, which can cause fatigue, headache and possible blurring, or diplopia upon looking away from the paper. This condition may be associated with pseudomiopias or spasms of accommodation.

- Insufficient divergence: Difficulty in relaxing eye convergence at distance. May cause intermittent diplopia, headache, fatigue, nausea and photophobia.

- Too much divergence: Difficulty in eye convergence with maintaining alignment of the eyes at a distant. May cause occasional diplopia but normally suppresses an image to eliminate symptoms.

- Amblyopia
The condition where one eye is compensated by the appropriate correction but fails to achieve a visual acuity (VA) as good as the other eye. The origin of this problem can be organic (due to a disease) or functional (due to the different abilities of the eye have not been able to develop because it is not detected early). May be associated with strabismus.

- Strabismus
Occurs when one of the two visual axis are not directed to the fixation point so that there is no simultaneous fusion or three-dimensional perception (stereopsis). It basically classified into different types according to where the eye turns and the time when it appeared.

- Eye movement disorder: The visual and motor development is closely related especially in regard to the control of oculomotor movements. The control of eye movement is essential in analyzing the visual information. To achieve this requires a good anatomical and functional integration of the eye muscles that depends on proper coordination with binocular and proper innervations and normal anatomy.

There are three types of oculomotor movements:

- Fixation
Maintaining visual fixation on a particular stimulus. Only when the eyes are still on a stimulus can we discriminate and know what it is. It is related to attention.

- Smooth pursuits movement
Oculomotor movement that keeps the fixation on a moving stimulus.

It is a very important skill in sports, for example, in tracking a ball when running to catch up in football, tennis, basketball, etc.

- Saccadic eye movement
Oculomotor movement that can jump from one point to another.

We do the most precise saccades when we are reading or writing.

Oculomotor problems can cause:

• Difficulty or inability to maintain attention.
• You lose your place when you read.
• Skip words when reading.
• Transposition of letters or words.
• Make up words.
• Difficulty copying from the blackboard.
• Use your finger as a guide.
• Problems with reading comprehension.
• Dizziness with movement or going by car.
• Poor performance sports, especially those related to the ball.

- Eye focusing problems: When the focusing ability is impaired headaches, poor performance in reading, tendency to myopia, etc can occur. The most common disorders that cause these problems are:

- Accommodative insufficiency
Difficulty focusing at close distances so the focus is placed behind the plane of view.

- Excess accommodative
A tendency to focus too much so the focus is placed in front of the plane of view.

- Accommodative Inflexibility
Difficulty in changing the approach to efficiency and speed at different distances.

- Perceptual problems: The visual perception skills are what allow us to recognize what we see and interpret it correctly according to our previous experiences. In everyday activities we need adequate visual processing and good visual-motor integration.

Visual perception is mainly characterized by the following 7 skills:

- Visual Discrimination
The ability of the person to find the exact characteristics of two ways, when one is among similar form. Can lead to confusion of similar words in which only one letter is changed. Example: was - saw

- Visual memory
The ability of the person to immediately recall all the characteristics of the observed shapes or objects and be able to find this form or similar object between.

- Visual spatial relationship
Relating the vision and three-dimensional space. The ability to determine the orientation or configuration of objects of the same shape but in a different orientation. Example: the recognition of the letters d and b. The configuration of letters is the same, but the orientation gives a meaning or another depending on the orientation of d (letter "d" left-oriented) and b (letter "b" facing right).

- Form constancy
The ability to recognize the same shape, regardless of size and orientation, when it is among other shapes. They have difficulty in recognizing the same symbol differently.

- Visual sequential memory
The ability of the person to remember a number of shapes in a series immediately after the observation. It is used to sort letters (the alphabet) or spell words.

- Figure - ground
The ability of the person to perceive a visual shape or object, and find it from a diffuse surface. Example: the location of a particular word in a phrase or search for an exact phrase in a paragraph.

- Visual clousure
The ability of the person who has to, among a few forms or incomplete objects, come to recognize the full form. The construction of a puzzle (we have a few pieces each with similar characteristics, which together form a complete picture). It helps us understand what we read or draw logical conclusions.

The optometrist has full knowledge and tests available to assess and diagnose the state of these skills and if they are affected they can recommend vision therapy treatment.