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157 Cards in this Set
- Front
- Back
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Ocular Oscillations
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Movement of the eyes
Voluntary or involuntary Physiological or Pathological Fast, slow, or both movements |
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Normal eye mobements have two components
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fast phase (saccades)
Slow phase (pursuit) |
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Ocular Flutter
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Pathology
Back to back saccades no ISI |
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Which phase system is ocular flutter a pathology of?
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Fast
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Pathological Square wave jerks/ square wave oscillation
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acquired defect
2-5 degrees normal ISI |
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natural funtional response to prolonged relative motion, comprising alternate cycles of fast and slow phases
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Physiological Nystagmus
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Four physiological nystagmus
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vestibular
optokinetic end point rebound |
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Head rotations stimulate the labyrinths, excites the labyrinths on the side of rotation, inhibits the trailing labyrinth
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Vestibular Nystagmus
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the eyes track the moving scene with a slow eye movement, at a certain amplitude or velocity of ocular dispacement the postion of the eyes is reset by the fast phase, continued stimulation leads to repetitive cycles
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OKN
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Characteristics of OKN
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waveform is "saw tooth"
it has a linear slow phase velocity |
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is is the motion of the visual scene that causes the nystagmus and it is mediated by retinal slip
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OKN
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caused by looking into far lateral gaze
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End Point Nystagmus
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not always present ~45%
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End Point Nystagmus
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Jerk nystagmus
fast phase toward the target in lateral gaze slow phase pulls the eye back to the center of the orbit |
End Point Nystagmus
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nystagmus diminished over time
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End Point Nystagmus
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a reversal of EPN
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Rebound Nystagmus
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damp after a short period of time
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Rebound Nystagmus
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Greater in the dark
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Rebound Nystagmus
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Pathological (Aquired) Rebound Nystagmus
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Clinically observable
oscillopsia prolonged RN associated gaze paretic nystagmus |
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Congenital Ocular Oscillations
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Latent nystagmus
spasmus nutans infantile nystagmus syndrome (congenital nystagmus). |
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Pure _______ is rare
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Latent Nystagmus
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ALWAYS associated with strabismus
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Latent Nystagmus
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About 50% of patients with strabismus have this
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Latent Nystagmus
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this nystagmus is enhanced when one eye is covered
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Latent Nystagmus
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this is horizontal and conjugate
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Latent Nystagmus
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fast phase beats away from the covered eye
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Latent Nystagmus
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slow phase velocity is decreasing or linear and decays over time
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Latent Nystagmus
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the characteristics of the nystagmus follow Alexander's law
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Latent Nystagmus
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the nystagmus is greates when looking in the direction of the quick phase and some patients turn their head to keep their viewing eye adducted because in this position the nystagmus is minimal
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Latent Nystagmus
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Onset is 4 to 18 months of age
resolves in the middle of infancy (by 3yrs) has mostly a horizontal eye movements the intensity in each eye may be different eye movements are DISCONJUGATE head shaking (nodding) Torticollis |
Spasmus nutans
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Also referred to as:
infantile nystagmus syndrome or early onset nystagmus |
congenital nystagmus
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Involuntary eye movements
Horizontal component Conjugate eye movements Onset in early infancy (0-4 mths.) Can be idiopathic or inherited No oscillopsia |
congenital nystagmus
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An accelerating slow phase
Slow phase takes eye off the target, increasing speed over time. Fast phase brings eye back to the target (foveating saccade). |
congenital nystagmus
waveform |
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the velocity of the movement waxes and wanes
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pendular
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the slow eye movement takes the eye off the target and the fast eye movement brings the eye back to the target.
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jerk
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how many basic waveforms are there for congenital nystagmus?
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2
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Foveation time
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the patient used one part of the waveform to see. It is when the mystagmus has stopped, after the eye has returned to the target, and/or when eye movement is very slow.
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For good VA speed should be
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less than 4 degrees per second
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often damps with convergence
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congenital nystagmus
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often has a null postion
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congenital nystagmus
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patients often use a head turm
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congenital nystagmus
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the intensity of the nystagmus changes with mental state
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congenital nystagmus
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orbital eye position where the nystagmus intensity is least
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null zone
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pursuit is always broken
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congenital nystagmus
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OKN can be reversed
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congenital nystagmus
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can demonstrate head shaking
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congenital nystagmus
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motion perception thresholds can be raised
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congenital nystagmus
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Subcategory of congenital nystagmus
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Congenital periodic alternating nystagmus (PAN)
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Horizontal jerk nystagmus
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Congenital periodic alternating nystagmus (PAN)
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Oscillopsia is rare
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Congenital periodic alternating nystagmus (PAN)
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left-beating nystagmus
transition phase right-beating nystagmus transtion phase |
A cycle of PAN
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cycles are long (4-5min)
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PAN
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cycles can be asymmetric
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PAN
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Patients often use only one head turn
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PAN
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This is a nystagmus caused by a neurological event. The patient complains of oscillopsia. The nystagmus is spontaneous, horizontal and often present in primary gaze, and the fast pahse reverses direction approximately every 2 min.
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Aquired PAN
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Etiology of Aquired PAN
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Cerebellar disease
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Baclofen
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damps nystagmus (only aquired)
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CN associated disorders:
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albinism
achromatopsia optic nerve hypoplasia Leber's amaurosis colobomata aniridia |
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Conservative treatment of Congenital Nystagmus
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Auditory biofeedback
use of prisms (deviation prisms, used to put the eyes in the place of least nystagmus) |
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Surgical Treatment of CN
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to correct specific, constant, stable anomalous head posture (Kestenbaum/Anderson)
To improve VA/ moderate AHP (dampen nystagmus, four muscle recession, tonometry) |
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What is memantine and gabapentine used for?
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to improve VA, reduce nystagmus intensity and improve foveation in congenital nystagmus.
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Internally directed eye movements
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postitional shifts based on spaces in the text
text processing comprehension short-term memory general interest cognitive factors |
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when stationary text is being read eye movements are _____________
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internally directed within the subject
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Characteristics of the normal reading pattern
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1. Fixations
2. Regressions 3. Return-sweep saccades 4. Average span of recognition and perceptual span 5. Fixation duration 6. Reading rate |
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refers to the total number of "eye stops" during reading
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fixations
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If the material is more difficult you have (more or less?) fixations
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more
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as word length increases
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fixating the word increases
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most words are fixated
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only once
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eye movement
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left to right progressive saccades
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interfixation movements
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1*-2* (range 0.5-4*) in angular extent- the eyes move from one fixation point to another
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Saccadic duration (fixation)
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10-30 msec
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Average sccade length
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8 characters (range: 1-18 characters)
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the percentage of total reading time taken up by actual eye movements themselves is no greater than
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10%, with an average of 7%
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fixations that are directed from right-to-left by "backward" or regressive movements
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regression
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Most are only a few characters in extent
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regressions
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reflects text confusion and comprehension problems
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regressions
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"re-check" or "double check" confirmation
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regressions
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what percentage of saccades are regressions
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10-15%
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which are refixed more........uncommon words or common words
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uncommon words
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large right-to-left slightly oblique saccadic eye movement that shifts the eyes from near the end of one line to near the beginning of the next line of the text
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Return-sweep saccade
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Begins approximately 6 character spaces from the end of one line to the 6th character space of the next line
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Return-sweep saccade
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what is the typical angular extent of return sweep saccades
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12-20 degrees
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what is the saccadic duration of return sweep saccade
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40-54 msec
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the amount of print that one can perceive and process with each fixation
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average span of recognition and perceptual span
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the length of time in msec that the eye pauses or remains fixated on a word
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fixation duration
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average fixation duration
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225msec (refractory period is 200msec sor 25msec for comprehension)
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fixation durations is
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shorter for easier text and longer for difficult text
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fixation duration varies with
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ambiguity
grammatical function predictability |
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when is visual information extracted?
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only during fixation periods
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when does saccadic suppression occur?
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during the interfixational saccades
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the number of words read per unit time and is usually specified in words per minute (wpm)
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reading rate
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vergence dynamics during saccades
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a transient over convergence (0.1-0.3 degree) followed by corrective dynamic divergence response (approximately 300 msec in duration)
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dyslexia- 2 basic categories
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1. developmental/ congenital
2. aquired |
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refers to specific reading disablities
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Developmental/ Congenital Dyslexia
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at least two years behind expected grade level of reading
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Developmental/ Congenital Dyslexia
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normal intelligence, normal sensory vision, and no neurologic or emotional disorders
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Developmental/ Congenital Dyslexia
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two types of Developmental/ Congenital Dyslexia
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1. Language-deficit dyslexia
2. Visual-spatial dyslexia |
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their abnormal reading eye movement patterns reflects a basic problem in the processing of language
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Language-deficit dyslexia
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increased number of progressive and regressive movements
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Language-deficit dyslexia
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small amplitude saccades
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Language-deficit dyslexia
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prolonged fixation durations when reading text appropriate for their age level
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Language-deficit dyslexia
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material that is appropriate for their reading level, yields a normal reading pattern
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Language-deficit dyslexia
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show inaccuracy of the return-sweep saccade
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Visual-spatial dyslexia
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frequent right-to-left sequence saccades
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Visual-spatial dyslexia
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partial and complete "reverse staircase" patterns
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Visual-spatial dyslexia
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independent of the level of reading material
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Visual-spatial dyslexia
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reflects a problem in the processing of visual-spatial relations
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Visual-spatial dyslexia
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refers to the presence of a reading disability in a previously normal reader subsequent to neurologic dysfunction or damage, such as a stroke
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Aquired Dyslexia
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Aquired Dyslexia- characteristics
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1. reading difficulty
2. reduced comprehension 3. difficulty in sequencing of eye movements 4. problems with fixation 5. necessity to move the head to read |
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when there isnt any evidence of abnormal ocular motor control, reading eye movements appear similar to language-deficit dyslexia
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Aquired Dyslexia
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The DEM test
three subetests: |
1. a pre-test
2. two vertical sub-tests 3. a horizontal sub-test |
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an abbreciated horizontal array of numbers used to assess number knowledge and articulation
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The pre-test
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the child should be able to read aloud all of these numbers in 12 seconds or less
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Pre-test scoring
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dependent on patient's visual-verbal automatic calling skills
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The vertical sub-test
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the patient is instructed to read the numbers down the columns as quickly as possible and are NOT allowed to use finger to guide reading
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Vertical Subtest A
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repeat of test A
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Vertical Subtest B
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consists of numbers in an unusually non-symmetric horizontal array
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The horizontal subtest
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the patient is instructed to read the numbers across the rows as quickly as possible and time and errors are recorded
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Horizontal array: test C
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Errors
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1. substitution
2. omission 3. addition 4. transposition |
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scoring
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latency: horizontal time divided by vertical time
accuracy: sum of errors from total test |
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more on scoring
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the ratio and number of errors for a patient are compared to normative values to determine a percentile rank for the patient consistent with his or her performance and age.
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normal for age for DEM test
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14th percentile or above
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Interpretation of DEM test
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by comparing performance on the vertical and horizontal subtests, the DEM test accounts for the effects of number recognition, retrieval and visual-verbal integration skills.
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round hole in the center of the iris
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the pupil
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the aperature of the eye's optical system formed by the iris
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the pupil
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optical functions of the pupil
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1. regulates the amount of light reaching the retina
2. increases the depth of focus 3. reduces the crystalline lens chromatic and spherical aberrations 4. produces the phenomenon of apparent accommodation 5. conveys social information |
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The size of the pupil varies:
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1. at different ages
2. from person to person 3. with different emotional states 4. levels of alertness 5. degrees of accommodation 6. ambient room light |
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does not change with increasing levels of luminance that stimulate only retinal rods
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pupil size
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leads to a pupil size decrease from a maximum with an increase in 2 log units of luminance
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retinal cone stimulation
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normal pupil diameter
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3-4mm
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smaller in infancy, larger in childhood, progressively smaller with age
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pupillary diameter
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pupil size relates to varying interactions between the:
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sympathetically innervated iris dilator, supranuclear control from the frontal lobe, occipital lobes (accommodation), responds to respirations
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physiological anisocoria
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20-40% have a slight difference in pupil size ~0.5mm.
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the iris is the anterior extension of the?
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ciliary body
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iris root/ color
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approximately 12mm
margin diameter: 0.8-1.0mm color- darker with age |
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ciruclar band of muscle that surrounds the pupillary margin and constricts it when activated (parasympathetic activation)
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sphinter pupillae
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consists of radially oriented muscle fibers tht draw the pupil open from the periphery (sympathetic activation)
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Dilator iridis
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light reflex- testing
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bright light into one eye after patient has been in a dimly illuminated room for about 10 seconds
both pupils constrict and dilate by equal amounts direct light reflex consensual light reflex |
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neuro-anatomy
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the light reflex is entirely subcortical
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in optic nerve, exit optic tract prior to later geniculate, enter midbrain via brachium of superior colliculus and synapse into pretectal nucleus
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Afferent fibers
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each pretectal nucleus decussates neurons to the cerebral aqueduct to the ipsilateral and contralateral Edinger-Westphal nucleus of CN III
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Afferent fibers
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via CN III to the ciliary ganglion in the lateral orbit
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efferent fibers
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the postganglionic fibers go via the short ciliary nerve to innervate the sphincter muscle of the iris
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efferent fibers
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near triad
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vergence, accommodation, pupillary constriction
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PERRLA
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pupils
equal round reactive to light accommodative stimulation |
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Relative afferent pupillary defect (RAPD)
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if an optic nerve lesion is present, the direct light response in the involved eye is less intense than the consensual response evoked when the normal eye is stimulated
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Causes of unilateral decreased vision without an afferent pupillary defect:
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1. refractive error
2. couldy media (cataract) 3. amblyopia 4. hysteria or melingering 5. a macular lesion 6. chiasmatic problems |
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Amaurotic pupillary defect
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an eye that does not even see light owing to severe unilateral retinal or optic nerve disease
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argyll robertson pupil
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the pupil is less than 3mm in diameter, does NOT respond to light stimulation, does accommodate (bilateral), CNS syphilis (50%)
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types of pupils in argyll robertson pupil
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irregular, eccentric, dilate poorly with mydriatics as a consequence of concomitant iris atrophy
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an incomplete argyll robertson pupil can be caused by:
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1. diabetes
2. chronic alcoholism 3. encephalitis 4. multipe sclerosis 5. CNS degeneration disease 6. tumors of the midbrain |
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due to an abnormal pupillary constrictor mechanism in which all or a portion of the sphincter muscle contracts slowly to near stimulation and relaxes even more, but either response is better than the light response
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Tonic pupil
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associated with loss of deep tendon reflexes (Adie's syndrome)
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Tonic pupil
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results from damage to the ciliary body
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Tonic pupil
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caused by a lesion affecting the sympathetic nerve supply at any point alongs its pathway from the hypothalamus
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Horner's Syndrome
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Horner's Syndrome- signs
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1. slight unilateral ptosis
2. miosis of the affected eye 3. ipsilateral anhydrosis 4. heterochromia iridis 5. no associated ocular motor defects |
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interruption of the sympathetic fibers results in a small pupil which retains its light response
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monocular miosis
Horner's Syndrome |
