(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AG) Class of 2022, Baylor College of Medicine, Houston, Texas
Subject
Kinetic Dissociation; Visual Field Testing
Description
Summary: 1. Riddoch Phenomenona. Stat o kinetic dissociation: you can't see a stationary stimulus (static) but you can see a moving stimulus (a kinetic) b. Visual field testing i. Humphrey 1. Static test where stimulus (dots) are presented in each hemi-field ii. Goldmann 1. Kinetic test where the stimulus is moved from the non-seen part of the field into the seeing part iii. For example, a patient with Riddoch Phenomenon can show a left complete homonymous hemianopsia on the Humphrey test and have a normal Goldmann test c. Very uncommon phenomenon i. When seen it's often seen in occipital lesions where there's a dissociation in the pathways between motion related stimuli and static related stimuli d. Typical patient presentation i. 80 year old who has: 1. painless progressive loss of vision 2. left homonymous hemianopsia 3. an MRI that only shows posterior cortical atrophy 4. ability to see kinetic stimuli
Transcript
So today we're going to be talking about the Riddoch phenomenon and basically what this is is a dissociation between static stimuli (stationary stimuli) and kinetic stimuli which is moving stimuli. So when we have statokinetic dissociation it means you can't see a stationary stimulus (static) but you can see a moving stimulus (a kinetic). So for example in a patient who has a Humphrey visual field the dots are presented in each hemi-field and so if you have a homonymous hemianopsia on a Humphry visual field that is going to be static perimetry. So static perimetry are dots testing in each location but they don't move. As opposed to kinetic perimetry, which is hard to find nowadays, but Goldmann perimetry would bean example of that -so where the stimulus is moved from the non-seen part of the field into the seeing part and it generates isopters linking the same stimulus size test object into an oval that represents the hill of vision with the tip of the hill being the fovea and the various rings representing different sizes of the stimuli. So these are brought in kinetically vs. Humphrey where the lights are presented statically in the same location. And so literally a patient who has the Riddoch phenomenon might have a left complete homonymous hemianopsia on the static perimetry and a totally normal Goldmann kinetic visual field. So that dissociation between static and kinetic is a very uncommon phenomenon it's often seen in occipital lesions where there's a dissociation in the pathways between motion related stimuli and static related stimuli. And so you should really be thinking about occipital type things. And so in a left homonymous hemianopsia it would be looking at the right occipital lobe obviously. And so atypical patient might be a 80 year old who has painless progressive loss of vision, has a left homonymous hemianopsia, but the MRI only shows posterior cortical atrophy. And if we do the kinetic stimuli suddenly they can see. You're going to be tempted to say that they're not organic because they just saw in a place that you said they didn't see. But you have to recognize statokinetic dissociation, the Riddoch phenomenon could be accounting for that phenomenon where they can see a moving target but not a static target.
