Flashcards in Fixational Eye Movements (M1) Deck (53):
If a nystagmus is possibly acquired, what should be looked for?
1. null point
2. foveation periods
3. oscillopsia (will have in acquired)
4. abnormal head posture (opposite to side of null position)
5. direction of nystagmus
Is gaze-evoked jerk nystagmus acquired or congenital? 1. What induces it? 2
What are the types of saccadic intrusions that are abnormal fixational eye movements?
1. square-wave jerk
2. macro square-wave jerk
3. macrosaccadic oscillation
What causes macrosaccadic oscillations?
saccade movement occurs randomly and realize, then have saccade back to target but overshoot and repeat until on target
Are constant velocity slow phase (saw-tooth) nystagmus jerk wavefronts acquired or congenital? 1. Where is the damage? 2
1. acquired or physiological (post-rotational or hot water in ear (caloric))
What are the causes of an acquired nystagmus?
4. infection in brain
6. alcohol intoxication
7. medications such as phenytoin, anti-seizure meds, sedatives
What is the abnormal fixational eye movement that is common in amblyopia and is monocular? 1. What is the amplitude? 2. Velocity? 3. What corrects it? 4
1. slow drift
2. 1deg or less
3. less than 3deg/s
What is the appropriate treatment for saccadic intrusions?
refer because brain disease
What is the amplitude of square-wave jerk saccadic intrusions? 1. What could this indicate in a patient? 2
1. 0.50 to 5deg
2. cerebellar disease or MS
What is the amplitude of macro square-wave jerk saccadic intrusions? 1. What could this indicate in a patient? 2
1. 5 to 10deg
2. cerebellar disease or MS
What is the direction in which intensity = (frequency X amplitude) of nystagmus is least and visual acuity is optimal called?
What does the area over which fixation varies about the point of regard increase with?
What type of nystagmus has the eyes moving back in forth in a sinusoidal pattern?
What are the management options for congenital nystagmus?
1. prism to move images to null point
2. BO prism to increase convergence demand
3. 2 muscle procedure: surgery to move null point to primary gaze (strengthen or weaken muscles)
4. Tenotomy surgery/combined procedure
What types of jerk nystagmuses have a decelerating slow phase?
1. gaze evoked
2. latent nystagmus
What are the types of nystagmus?
Is latent nystagmus acquired or congenital? 1. What type of phase does it have? 2. When does it become significant? 3
2. decelerating slow phase jerk
3. when cover one eye
While performing visuoscopy, if the foveal reflex is on the first ring inferior to the eccentric point, what is the amount and direction of eccentric fixation?
1 pd superior
What is the idea that fixation tends to vary more along one direction of gaze?
What is different about a Hirschberg test compared to a angle Kappa? 1. What is Hirschberg used to test? 2
1. done binocularly
What is used to determine what microsaccades are used for?
stabilized retinal image technique
What is the clinical test that views the macula with the direct ophthalmoscope using the fixation target setting to determine if they are fixating appropriately?
What are miniature or micro-eye movements that are constantly occurring as we fixate on a target?
fixational eye movements
What is a characteristic of a nystagmus is which the a point in that waveform when the eye is not moving, the pt will intentionally put that on the target and acuity can get better will really pay attention to that snippet in time when their eye is not moving called?
What are the main characteristics of congenital nystagmus?
1. usually a null position
2. often reduction in nystagmus with convergence
3. foveation periods
4. don't have oscillopsia
5. patient turns head opposite to null position
6. only horizontal
While performing visuoscopy, if the foveal reflex is on the second ring temporal to the eccentric point, what is the amount and direction of eccentric fixation?
2 pd nasal
What should be done for a patient with a latent nystagmus when doing monocular VA's in order to prevent eye movement?
blur one eye (Humphriss refraction)
What is the average result for the corneal reflex if the patient has central fixation when using a penlight to assess "angle Kappa"?
0.25-0.5 mm nasal (+) to center of entrance pupil
What percentage of patients with strabismus have nystagmus? 1. Percentage of patients with congenital nystagmus have strabismus? 2
What are the normal values of microsaccades that are considered noise?
1-2 per second, 1-25' of arc range (rarely above 10')
Why do saccadic intrusions occur?
at some point saccadic movement happens away from target, then get movement back to target once realize
If the fixation of a patient during visuoscopy is not central, what is it considered? 1. What needs to be analyzed for this patient? 2
2. direction and magnitude of eccentric fixation in prism diopters
What type of nystagmus is associated with drug or alcohol use?
gaze evoked decelerating slow phase nystagmus
What are the normal values of a tremor that is considered noise?
30-100Hz, 5-30" arc
What is a visual disturbance in which objects in the visual field appear to shake back and forth?
What is the amount of prism diopters that accounts for a 1mm shift in angle kappa?
What are the normal values of a drift that is considered noise?
1-8" of arc/sec (2-5" of arc probably noise)
What is a tracking movement in response to a global movement (ie bus moving in front of you)?
Are accelerating slow phase nystagmus jerk wavefronts acquired or congenital?
What type of jerk nystagmus is monocular and has no clinical significance?
Is slow drift slower or faster than regular drift?
What are the causes of congenital nystagmus?
3. congenital cataract
4. optic nerve hypoplasia
What is a sequence of increasing amplitude and decreasing amplitude saccades to either side of the fixation point called?
What is the procedure to manage congenital nystagmus that cuts off all horizontal recti and attach in same position or change position of muscle?
What is it called when the null position shifts around over several minutes or longer?
periodic alternating nystagmus (PAN)
What type of visual disorder is eccentric fixation commonly found in? 1. Is this monocular or binocular? 2
1. strabismic amblyopes
2. purely monocular
What is the equation to predict the VA for someone with eccentric fixation?
MAR (minimum angle of resolution) = EF (mag of eccentric fixation) + 1
What should be done while performing a visual field on a latent nystagmus patient?
do it binocularly
What is it called when a patient intentionally looks off to the side of the object of regard because if they look straight ahead they cannot see it? 1. When is this utilized? 2
1. eccentric viewing
2. pt's with central scotomas
What may cause acquired fixational abnormalities?
5. MS (esp in brainstem, cerebellum, vestibular system)
What can demonstrate fading of stabilized retinal images without a stabilization apparatus with careful fixation?
Which fixational eye movement type result in improvement in visibility?