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.
Saccadic eye movements are quick, tiny shifts that our eyes make when we look from one point to another. These movements happen so naturally that we hardly notice them. But, believe it or not, they play a crucial role in how we interact with our environment.
According to scientific research, our eyes make approximately 3 saccadic movements per second, which adds up to hundreds of thousands each day!
One of the most common vision deficiencies are oculomotor dysfunctions, which are deficiencies in saccadic eye movements, pursuits, and fixation. Oculomotor deficiencies are normally identified in school aged children because they interfere with academic and sports performance, however they are also often identified after a head injury.
One of the most common uses of saccadic eye movements is during reading and writing. Our eyes move from word to word and line to line, allowing us to absorb the information. Without these quick movements, reading would be a laborious process. One thing to point out is that when a child needs to work extremely hard to read, this often causes a lack of motivation, which is commonly misinterpreted as a behavioral problem.
Here is a basic passage that a first-grader should be able to read, along with how they might read it if they have issues with saccadic eye movement.
The dog ran after the ball.
The dog jumped over the fence.
The dog caught the ball and wagged its tail.
Impaired Saccadic Eye Movement Reading
The ran after ball.
The dog over the fence.
The caught ball wagged tail.
The sun was shining brightly.
The kids were playing in the yard.
They all enjoyed a fun game of tag.
Impaired Saccadic Eye Movement Reading
The was shining.
The kids playing yard.
They all a fun of tag.
When driving, our eyes constantly jump from one focal point to another—checking mirrors, reading road signs, and keeping an eye on the traffic ahead and around us. Saccadic movements help us compile all this information swiftly, making us more effective and safer drivers.
In sports, especially fast-paced ones like tennis or basketball, your eyes are continually moving to track the ball, players, and other elements in the game. Effective saccadic movements help in improving your reaction time and overall performance.
Even while watching television or working at a computer, our eyes are busy making saccadic movements as we scan the screen, read text, or focus on different elements like images or headlines.
Eye movements are also crucial during conversations. We use them to make eye contact, read facial expressions, and even signal non-verbal cues. Effective eye movements can aid in better communication and more meaningful social interactions.
Whether you're walking through a crowded area or maneuvering around obstacles, your eyes guide you through. Quick eye movements help you assess the environment and make real-time decisions to navigate safely.
When you're shopping or cooking, you often have to quickly scan your environment to find specific items or read labels. These activities require well-coordinated eye movements.
Certain jobs, like those in construction, aviation, or even optometry, require specialized use of saccadic eye movements to focus on various details quickly and accurately.
Below are some signs that suggest a child might be experiencing issues with saccadic eye movement:
Traumatic brain injuries can have a profound impact on various functions of the body, including vision. Saccadic eye movements, which are vital for daily activities like reading and driving, can be significantly affected by brain injuries.
In a study, researchers used a Wii Balance Board and a soccer game to study eye movements in people who had sports-related concussions. They compared these people to athletes who didn't have concussions. They found that the people with concussions had eye movements that were bigger and faster than normal, and they had trouble smoothly following moving objects.
This fits with an older study that also found people with concussions, from various causes, made more mistakes in directing their eye movements. These people had trouble with the accuracy of where they were looking. It's worth noting that the older study included people with more severe symptoms like loss of consciousness, which might have made the results more noticeable.
In short, both studies suggest that concussions affect how accurately and smoothly people can move their eyes.
One of the most common effects of brain injuries on saccadic eye movements is a reduction in speed and accuracy. Patients may experience delays in initiating eye movements, or their eyes might not land precisely where intended.
Brain injuries can disrupt the coordination between both eyes, causing them to move out of sync. This can lead to double vision and make tasks like reading or driving more challenging.
The automatic, reflexive saccades may become sluggish or imprecise. This can compromise your ability to quickly focus on unexpected stimuli, which is crucial for activities like driving.
Voluntary control over eye movements can also be compromised. Initiating a voluntary saccade may become difficult, and there may be an increased rate of errors, such as overshooting or undershooting the target.
Brain injuries can specifically impair your ability to perform antisaccades, making it difficult to look away from a distracting stimulus. This can be particularly troubling for tasks that require concentration.
These minute adjustments in eye position can be affected, leading to visual fatigue and difficulty maintaining a steady gaze.
In some cases, brain injuries might lead to an unusual increase in express saccades, making it challenging to focus on a single point for an extended period.
If you or someone you know has had a TBI, it's essential to consult your eye care professional for a functional eye exam, which can help evaluate the state of your visual system, including saccadic eye movements.
A recent study provides evidence that children with dyslexia, ADHD and Developmental Coordination Disorder were found to have worse outcomes of saccadic eye movement than in the group of children without neurodevelopmental disorders. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8293429/)
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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:
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:
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.
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.
Strengthening the brain-eye connection for better awareness and positioning.
Horizontal and Vertical Drills
Training the eyes to move smoothly across both horizontal and vertical planes.
Enhancing the ability to keep track of symbols or letters during quick eye movements.
Improving the eyes' ability to adapt to new visual information.
Incorporating other body movements to enhance eye-hand coordination.
Regular evaluations ensure that the therapy is tailored to each individual's progress, making vision therapy an effective approach to improving saccadic eye movements.