What are Saccades and What Role Do They Play in Our Life?

Discover the essential role of saccadic eye movements in daily life, types of saccades, and how they're affected by brain injuries and other conditions.

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Skipping Lines When Reading? How saccadic eye movements impact us

Table of Contents

Why Eye Movements Are Critical for Reading and Writing
Symptoms and signs of issues with saccadic eye movements
How Traumatic Brain Injuries Affect Saccadic Eye Movements
Different Types of Saccadic Eye Movements
Medical Conditions That Can Impact Saccadic Eye Movements
Vision Therapy for Saccades
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When we look around, our eyes make quick, small jumps to focus on different things. These jumps, called saccadic eye movements, are a key part of how we see the world. Even though these movements happen smoothly and without us noticing, they are vital for us to interact with our environment.

How Often Do Our Eyes Move?

Studies show that our eyes make these quick movements about 3 times every second. This adds up to hundreds of thousands of times a day, highlighting how important they are for our daily vision.

Eye Movement Problems

Some people have trouble with their eye movements, including saccadic movements, slow tracking movements, and keeping their eyes steady. This issue is common in school-aged children and can affect their learning and sports. Adults can also have these problems, especially after a head injury. Finding and treating these eye movement issues is important for good vision and health.

Why Eye Movements Are Critical for Reading and Writing

Saccadic eye movements are crucial for efficient reading and writing, enabling our eyes to swiftly move from word to word and line to line. This seamless navigation through text is essential for comprehension and learning. Without these rapid eye movements, reading could become an exceedingly slow and difficult task. It's particularly important to recognize that when children exert excessive effort to read, it might lead to a decrease in motivation, often misinterpreted as a behavioral issue rather than a challenge with their visual processing.

Understanding Saccadic Movement Challenges

Challenges with saccadic movements can significantly impact how a child reads. Consider the following examples that illustrate the difference between normal reading and reading with impaired saccadic movements:

Example 1

Normal Reading: The dog ran after the ball. The dog jumped over the fence. The dog caught the ball and wagged its tail.
With Saccadic Movement Issues: The ran after ball. The dog over the fence. The caught ball wagged tail.

Example 2

Normal Reading: The sun was shining brightly. The kids were playing in the yard. They all enjoyed a fun game of tag.
With Saccadic Movement Issues: The was shining. The kids playing yard. They all a fun of tag.

Saccadic Movements in Daily Life

Driving: Saccadic movements are essential for driving, allowing us to quickly glance at mirrors, read road signs, and monitor traffic, enhancing our driving safety and effectiveness.

Playing Sports: In sports, such as tennis or basketball, effective saccadic movements are key for tracking the ball and observing players, improving reaction times and performance.

Screen Time: Whether watching TV or using a computer, our eyes utilize saccadic movements to scan the screen and focus on various elements, from text to images.

Social Interactions: Eye movements play a vital role in conversations, aiding in making eye contact, interpreting facial expressions, and conveying non-verbal signals, thus enhancing communication.

Navigating Spaces: In crowded or obstacle-filled spaces, quick eye movements guide us, helping to assess the environment and navigate safely.

Identifying Objects and Details: Activities like shopping or cooking require swift eye movements for scanning and reading labels, demonstrating the versatility of saccadic movements in our daily lives.

Job-Specific Tasks: Certain professions, including construction, aviation, and optometry, rely heavily on proficient saccadic movements for focusing on details swiftly and accurately, showcasing the broad applicability of these eye movements across various tasks and environments.

Symptoms and signs of issues with saccadic eye movements

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Recognizing the signs of saccadic eye movement issues in children is crucial for early intervention, which can significantly improve both academic performance and daily activities. Here are some indicators that may suggest a child is experiencing difficulties with saccadic movements:

Early detection of eye movement problems is key to helping kids do better in school and in their daily lives. Here are signs that a child might have trouble with their eye movements:

Trouble Copying Text

If a child often skips words or makes mistakes while copying, this might be due to eye movement issues.

Reading Hardships

Having a hard time reading several lines or keeping place without pointing might suggest problems.

Spelling and Test Struggles

Common spelling mistakes and varying test scores, especially under time pressure, could indicate eye movement challenges.

Writing Concerns

If a child's writing is uneven or poorly spaced, it might be related to eye movement difficulties.

Visual Discomfort

Blurry vision, seeing double, or feeling like words are moving on a page are signs of potential eye movement issues.

Short Attention

A limited attention span or getting easily distracted could point to eye movement problems.

Head Moves When Reading

Moving the head instead of the eyes while reading, or unusual reading postures, might signal difficulties.

Understanding Text

Problems with grasping or remembering what's read can indicate eye movement issues.

Math and Coordination

Trouble with math or coordination, affecting hand-eye coordination, might be linked to these problems.

Prefers Hands-On Learning

Needing to learn by doing rather than seeing could suggest eye movement challenges.

Physical Signs

Headaches or eye strain after reading tasks are physical symptoms of possible eye movement issues.

Sports Coordination

Problems with sports, depth perception, and feeling sick from motion might also be signs.

How Traumatic Brain Injuries Affect Saccadic Eye Movements

Traumatic brain injuries (TBIs), including concussions, can significantly affect many body functions, particularly vision. Saccadic eye movements, essential for tasks like reading and driving, are often impacted by these injuries.

How Concussions Affect Eye Movements

Studies on individuals with sports-related concussions have shown that these injuries can alter saccadic eye movements. Athletes with concussions may experience larger and faster eye movements and have trouble tracking moving objects smoothly. This suggests concussions can impair the precision and fluidity of eye movements, crucial for everyday activities.

Concussion Effects on Eyes

Slower Saccades: Concussions can slow down the initiation of saccadic movements, making eye movements less efficient.
Eye Coordination Problems: TBIs might disrupt the eyes' ability to move together, leading to double vision and difficulties with activities needing visual focus.
Challenges with Reflexive Saccades: The automatic nature of saccades may be affected, reducing the ability to quickly focus on new stimuli.
Difficulty with Voluntary Saccades: Controlling eye movements on purpose can become harder, causing more errors like overshooting or undershooting targets.
Antisaccade Issues: TBIs can make it difficult to look away from distractions, which is important for concentration.
Microsaccade Irregularities: These small, corrective movements may become erratic, causing visual strain and difficulty in maintaining a steady gaze.
Increase in Express Saccades: A rise in these quick saccades after a TBI can make it hard to maintain focus on one point for long.

Saccadic Movements in Neurodevelopment

Children with neurodevelopmental disorders such as dyslexia, ADHD, and Developmental Coordination Disorder also show differences in saccadic movements, highlighting the importance of these movements in cognitive and neurodevelopmental health.

Seeking Professional Help

For those affected by TBI, it's crucial to consult an eye care professional for a comprehensive eye exam. This can help assess how the visual system, including saccadic movements, has been affected and guide interventions for visual rehabilitation, improving daily life.

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Different Types of Saccadic Eye Movements

Saccadic eye movements might seem straightforward, but they can be broken down into different types, each serving specific functions. Knowing these can help you better understand the complexities of our visual system.

The Difference Between Saccades and Pursuits

Saccades

Quick, short eye movements
Used for shifting gaze
Can be voluntary or involuntary
Visual processing reduced during movement

Pursuits

Smooth, longer-lasting eye movements
Used for tracking moving objects
Generally controlled voluntarily
Visual processing continues during movement

Vertical Saccades

Vertical saccades allow your eyes to move up and down. These are crucial for tasks like reading a book, where your eyes must move from the end of one line to the beginning of the next. Vertical saccades are also important when you're walking, allowing you to look down at the path in front of you and then back up to see where you're going.

Common Uses

Reading and writing
Scanning up and down a computer screen
Navigating stairs
Looking up at signs or down at your phone

Challenges

Impaired vertical saccades can make tasks like reading or navigating stairs difficult and may indicate neurological issues. In some neurological diseases, such as Progressive Supranuclear Palsy (PSP), vertical saccades are more prominently affected than horizontal saccades.

Horizontal Saccades

Horizontal saccades allow your eyes to move side to side. These are crucial when you're reading, as your eyes move across a line of text. They're also essential for tasks like driving, where you need to look from side to side to assess the environment and traffic.

Common Uses

Reading and writing
Driving or cycling
Watching sports or following a moving object
Scanning a crowd or room

Challenges

Problems with horizontal saccades can make it difficult to track moving objects or read text efficiently. Impairments in horizontal saccades are often easier to recognize and can be associated with a variety of neurological or ophthalmic conditions.

Reflexive Saccades

These are automatic and occur in response to a stimulus. If a bright flash or sudden movement happens in your peripheral vision, your eyes will automatically jump to it. This kind of saccade is essential for reacting quickly to potential dangers, like a car suddenly pulling out in front of you.

Antisaccades

In certain situations, you need to look away from a strong visual or auditory cue. This is where antisaccades come into play. For example, if you're trying to focus on work but there's a distracting noise or movement, an antisaccade helps you maintain your focus and not look at the distraction.

Express Saccades

These are extremely quick eye movements, typically executed in less than 100 milliseconds. They're thought to be a result of practice and are common in activities requiring rapid focus shifts, such as video gaming or certain sports.

Microsaccades

These are tiny, almost imperceptible movements that occur even when you try to keep your gaze fixed. They prevent the fading of the visual scene by constantly refreshing the image on your retina.

Sequential Saccades

When your eyes jump between multiple points in a sequence, these are called sequential saccades. For example, when scanning a room, your eyes may jump from one face to another in a particular order.

Medical Conditions That Can Impact Saccadic Eye Movements

Saccadic eye movements can be affected by a variety of medical, eye-related, and neurological conditions. Here's a list of some conditions known to have an impact:

Progressive Supranuclear Palsy: Primarily affects vertical saccades
Traumatic Brain Injury: Can severely affect both speed and accuracy
Stroke: Depending on the affected brain area, can have a significant impact
Cerebellar Ataxia: Directly affects coordination and timing
Optic Neuritis: Can affect saccadic speed and accuracy
Strabismus: Affects coordination of eye movements
Retinal Diseases: Impair the visual input guiding saccades
Myasthenia Gravis: Fatigues the eye muscles, affecting saccades
ADHD
Autism
Childhood-onset schizophrenia

How does a Functional Optometrist Test Saccades?

A functional optometrist tests saccades, or quick eye movements, through various methods to understand how well a person's eyes are working. One commonly used test is the NSUCO oculomotor test, which is a quick and effective way to check the overall functioning of eye movements. In this test, the optometrist assesses four key factors:

Ability: How well the patient can stay on task.
Accuracy: The precision of the eye movements.
Head Movement: Whether the patient has to move their head excessively to follow the target.
Body Movement: How well the patient controls their body while their eyes are moving.

Some other tests that might be used include the Developmental Eye Movement (DEM) test and the King-Devick test. These look at reading speed, visual processing, and other linear visuomotor skills. Specifically, the DEM test can separate issues related to automatic eye movements from other factors, something the King-Devick test can't do.

Watch this video to learn more about the DEM test.

Advanced techniques, like the visagraph or readalyzer, use video-oculography to capture and analyze tiny eye movements. These high-tech tests can also provide an estimate of the patient's reading grade level.

Throughout all these tests, the optometrist will also observe for any compensatory actions like head movements or using a finger to guide reading, as these can indicate potential issues.

How Traumatic Brain Injuries Affect Saccadic Eye Movements

Vision Therapy for Saccades

Vision therapy is the treatment of choice for oculomotor dysfunction. Vision therapy offers various exercises specifically designed to improve saccadic eye movements. Here are some of the exercises and how they can benefit patients:

Targeted Saccadic Training

Individualized exercises help to directly train the eyes for quick, accurate movements.

Pencil Saccades: Patients focus on a word or letter on a pencil while it moves, honing their eye control and coordination.

Spatial Awareness

Strengthening the brain-eye connection for better awareness and positioning.

Hart Charts: Reading numbers or letters off a chart at varying distances and speeds can help in improving the precision of saccadic movements.

Horizontal and Vertical Drills

Training the eyes to move smoothly across both horizontal and vertical planes.

Wall Saccades: Patients focus on multiple targets on a wall, practicing quick shifts in eye focus without turning the head.

Letter Tracking

Enhancing the ability to keep track of symbols or letters during quick eye movements.

Ann Arbor Letter Tracking: This involves reading letters across a page as quickly and accurately as possible to boost saccadic tracking ability.

Adaptive Training

Improving the eyes' ability to adapt to new visual information.

Monocular Prism Jumps: Wearing prismatic lenses, patients practice quick focus changes, which trains the eyes to adapt to new visual scenarios swiftly.

Eye-Hand Coordination

Incorporating other body movements to enhance eye-hand coordination.

Marsden Ball: A suspended ball with letters or patterns is used. Patients track the ball's movement while reading or identifying the patterns, improving both saccades and eye-hand coordination. Learn more about Marsden ball.

Regular evaluations ensure that the therapy is tailored to each individual's progress, making vision therapy an effective approach to improving saccadic eye movements.

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