Today we will be discussing Saccadic Eye Movements. Again I have to tip my hat to Linda Sanet on this one because I love her description of Saccades as "Catching" movements. This to me is a great way to think about saccades, their purpose is to grasp a new object of regard by the fovea. Definition- Sudden voluntary change in fixation from one object of regard to another (definition via the Sanet Volumes). In addition to this sudden voluntary movement there is a certain type of “suppression” (for lack of a better term) or inhibition that takes place in order to avoid awareness of the visual smear during a saccade. :"Static visual stimuli are smeared across the retina during saccades, but in normal conditions this smear is not perceived. Instead, we perceive the visual scene as static and sharp. However, retinal smear is perceived if stimuli are shown only intrasaccadically, but not if the stimulus is additionally shown before a saccade begins, or after the saccade ends" (Campbell & Wurtz, 1978). As to exactly how the filtering process of that smear takes place is not known at this time though researchers think that it is inhibited at the LGN (Lateral Geniculate Body). In this section I also wanted to add a bit of information about the extraocular muscles since it is the firing of these muscles that drive saccadic movement.
For those of you who are interested in learning about the neurology behind eye movements below are links to a video from MIT Open Course Ware that deals with Neural Control of Visually Guided Eye Movements. The videos are lengthy and heavy but worth watching or bookmarking for future reference. Below is another video about eye movements up close and in slow motion. Symptoms/Signs when Deficient-
Therapy- In our office one activity we use early on in therapy to train saccadic accuracy is called Hart Chart Saccades and the procedure is as follows: Hart Chart Saccades Purpose: To improve the ability to organize and visually track while maintaining peripheral awareness. Materials: Letter Chart Technique: Level I – Straight Fixations 1.. The patient sits in a relaxed and balanced posture. 2. The Letter Chart is placed at eye level approximately 6’ away. 3. Instruct the patient to read the letters out loud in a rhythmic fashion without moving his head. The patient reads the entire chart proceeding in a left-to-right top-to- bottom fashion. Encourage the patient to maintain peripheral awareness of the whole chart and of other objects in the room. Level II – Line Interiors 1. Starting with the first line of letters, the patient reads out loud the 1st letter, then the last letter, then the 2nd letter, then the next-to-last letter, etc. Each line will be read from the ends to the middle in this fashion. 2. The patient is encouraged to maintain peripheral awareness of the whole chart and of other objects. Variations: 1. Use a metronome set to 60bpm 2..Add distractions such as saying other letters or repeating the alphabet. The assignment that goes along with this topic is as follows:
In the comments below please state your definition of saccades, the signs and symptoms (your own list) when deficient and detailed instruction for one therapy activity you use to address difficulty with saccadic eye movements. Please be as descriptive as possible for the benefit of the group and if you have any links or resources to share please feel free to do so here.
10 Comments
Lisa Folch
10/30/2016 07:36:20 pm
Definition of Saccades: "Rapid, ballistic movements of the eyes that abruptly change the point of fixation."
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Kristen Turner
11/1/2016 09:32:24 pm
Which programs on WSF do you run? We typically use 9-3, 9-4, and 9-6 but I am always looking for new ones!!
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11/12/2016 07:27:04 pm
In our office, we tape a small accommodative rock chart (the near chart when doing the near/far accommodative rock activity) to the center of the WSF and have patients read the letters on this chart as they use their peripheral vision to see lights. It helps them focus. We find fewer people "cheat" by looking.
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Shannon Sires
10/31/2016 11:39:58 am
Saccades are the rapid shifts in a patient’s fixations from one object to another. This skill is very important for academics, some sports, and job related activities. The goal for a saccades is to quickly and accurately jump their eyes from object to object.
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Natasha Lopatnikov
10/31/2016 07:13:15 pm
In our office we also use an activity called Door saccades. It's done standing up and with eye patch. We use 4 strips with letters first, then move to 4 charts. In the beginning patient read strips by 2 letters always starting from top left, then top right, then bottom left, then bottom right, that way they read all the letters. To load it up we ask them to read by 1 letter, or every other letters first, then come back and read the ones that they missed. To prevent memorization we shuffle strips or charts. To unload we cover part of it, also using flashlight pointing to letters helps too
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Lauren Ginoni
11/1/2016 11:58:50 am
Saccades are voluntary, quick, and accurate eye movements from one object in space to another object in space. These objects can be physical objects at different points in the environment, or jumping from word to word across a line of text. Good peripheral awareness is important for success with this skill.
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11/1/2016 12:37:09 pm
Saccades - Definition: Rapid or slow eye movement where the fixation of the eye is to be switched between targets.
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11/2/2016 04:32:56 pm
Saccades are rapid, voluntary, and accurate eye movements from one point of fixation to another. Peripheral vision (awareness) is very important for accurate saccades so that the patient knows where they are going with their eyes and can do it without overshooting or undershooting. Saccades should also be able to be performed without any head movement. Saccades are an essential skill for reading without losing your place.
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Pia Tan
11/3/2016 08:44:27 pm
Saccades are the ability of the two eyes to voluntarily and accurately move from one target to another. There are two types of saccades, gross and fine motor saccades. Our doctors test the gross motor saccades. When testing or working on saccades we look for over or undershooting, if the eyes are working together as a team, behaviour and for any posture or head/body movements. Head, tongue or body movement means there is gross motor overflow or involvement. We also want to look how accurate they Reach, Grasp then Release. Reach is fixating at one target, grasp is processing what was seen and release is the movement from one target to another. This skill is very critical for scanning and reading. you will need to explain this more as most will feel the reach grasp and release is moving from that target to another. For saccades to be successful, the person should be able to identify the target, know where the target is, know where he/she is with regards to the target with good central-peripheral integration. Difficulty with saccades may result into reading issues, fatigue, tired eyes, difficulty focusing and copying from the board, kinaesthetic tendencies and some may have a butterfly feeling/anxiety in their tummy while reading.
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11/13/2016 03:26:24 pm
Laurie Donnelly
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