Saccadic eye movements: characteristics and functions

Human vision encompasses various processes; saccadic eye movements are one of them. They are essential for the different activities we carry out in our daily lives and can even be related to some pathologies.

There are essential roles in each of the parts of our body that can be fascinating. Have you ever wondered: what are the mechanisms we use to pay attention when we talk to a person and pay attention to them by looking at them? What allows us to read or observe something carefully?

How do saccadic eye movements work?

Saccadic eye movements, also called refixation or saccades, They are as fast as they are simultaneous, and they occur when we look. Furthermore, these are controlled by our cerebral cortex and through the superior colliculus of our brain.

They favor the rapid movement of fixation from one point to another in our visual field. Thus, thanks to them we are able to map the environments in which we operate, as they make it easier for us to capture the images we see while we quickly move our gaze.

They help us when capturing details , so they need to be precise, and can be voluntary, involuntary or induced. To understand them better, think about the movements we make with our heads to observe our surroundings; What’s more, do this exercise trying to become aware of the saccadic movements of your eyes; Thus, you will better understand this quality.

Why are they provoked?

According to Gutiérrez de Piñeres Botero in his chapter “Human vision and eye movements” , They arise from their association with control. Volunteers and those that are induced by us appear when a specific visual stimulus catches our attention or when we respond to an order.For example, when they tell us to look in a certain direction.

Voluntary movements are accompanied by prosaccades and antisaccades. ; The former help us direct our gaze toward a new stimulus; The seconds ensure that we look away. For example, when we want to look someone in the eyes to convey attention from our non-verbal language.

The involuntary ones manifest themselves as an orientation reflex, which occurs when a stimulus suddenly appears that is outside the periphery of our visual field or when there is a novel stimulus. Therefore, are related to survival as they help us detect if there are signs of danger.

These functions can be evident when we read or have to follow something and attend to its details. For example, when reading for a long period of time we need these movements to keep our eyes on a word; when we try to follow something with our eyes, like an insect or when we want to pay attention to the details of a work of art.

Types of saccadic eye movements

Saccadic eye movements are divided according to the target. There are four.

Antisaccades. It is the movement we make when we move the eye towards the opposite place where the stimulus is located.Predictive saccades. They are those that help us follow trajectories and predict the behavior of what we are observing, for example, when looking at a car.Visually guided saccades. They occur when we need to capture what is being seen after the appearance of a stimulus in our visual field or simply when we need to capture something.Memory-related saccades. It is when we move our eyes to some point that we have in our memory, even though we are not actually contemplating the stimulus.

Saccadic eye movements were studied by Louis Émil Javal, Parisian doctor interested in optical instruments and eye movements. He did so after observing them in an experiment in which people had to read silently.

What pathologies are they related to?

Although not specifically a pathology, saccadic eye movements can be related to reading problems, above all, by needing precision; For example, dyslexia . So when movements fail they don’t maintain the duration they should or are inaccurate.

What causes this problem is that a letter cannot be correctly identified or the complete information understood. . It is usually common in children who compensate by moving their head, helping themselves with their finger or skipping sentences in the text they are reading. For this, the researchers evaluate whether students with a high number of saccades require help and intervention programs.

A pathology quite associated with these movements is attention deficit hyperactivity disorder. ; In this case, errors occur thanks to antisaccade movements and those that are visually guided. What this causes is that the details are fixed late, so it could become difficult to capture the details carefully.

On the other hand, these movements can occur involuntarily, causing vision to be reduced due to constant erratic movement of the eyes. TO This is called nystagmus and causes us not to see clearly or not be able to focus our attention carefully.

In sum, Every time we read, analyze an environment or attend to a conversation we are using saccadic eye movements. In other words, its function helps us bond with others, understand written words and survive.

You might be interested…