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55 Cards in this Set
- Front
- Back
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five functions of the pupil
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1. regulates amount of light reaching the retina
2. increases the depth of focus 3. reduces crystalline lens chromatic and spherical aberration 4. apparent accommodation 5. conveys social info |
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size of the pupil varies with...(6)
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1. different ages
2. person to person 3. different emotional states 4. levels of alertness 5. accommodation 6. ambient room light |
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how does luminance effect the pupil
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1. pupil size does not change with increasing levels of luminance that stimulate...only retinal rods
2. retinal cone stimulation lead to a pupil size decrease from max. with an increase in 2 Log Units of Luminance |
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what is normal pupillary diameter
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3-4mm
smaller in infancy larger in childhood progressively smaller with age |
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what stimulation causes pupil size to vary
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1. sympathetically inn. iris dilator
2. supranuclear control from frontal lobe 3. occipital lobes (accommodation) 4. respiration (hippus) |
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the iris is the anterior extension of...
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CILIARY BODY
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what is physiological anisocoria
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20-40% of population have slight difference in pupil ~0.5mm
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what are the two iris muscles
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1. sphincter pupillae (parasympathetic): circular band of muscle that surrounds the pupillary margin and constricts when activated
2. dilator iridis (sympathetic): consists of radially oriented muscles fibers that draw the pupils open from the periphery |
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light reflex is in what part of the brain
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entirely subcortical
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what is the light reflex nerve pathway after leaving the optic nerve
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1. optic nerve
2. optic tract to LGN 3. midbrain via brachium of superior colliculus and synapse in pretectal nucleus 4. each pretectal nucleus decussates neurons to the cerebral aquaduct to ipisilateral and contralateral Edinger Westphal nucleus of CNIII 5. CNIII to ciliary ganglion 6. sphincter muscle |
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what makes up the near triad
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1. vergence
2. accommodation 3. pupillary constriction |
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what does PERRLA stand for
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Pupils are Equal Round Responsive to Light-Accommodation
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what is RAPD
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relative afferent pupillary defect
1. 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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what are some causes of UNILATERAL decreased vision without an APD
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1. refractive error
2. cloudy media 3. amblyopia 4. hysteria or melingering 5. macular lesion 6. chiasmatic problem |
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what is 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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what is argyll robertson pupil
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1. the pupil is less than 3mm in diameter
2. does NOT respond to light stimulation 3. does accommodate (bilateral) 4. some degree of argyll robertson pupil is present in over 50% of patient with CNS syphilis |
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what are characteristics of argyll robertson pupil
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1. irregular
2. eccentric 3. dilate poorly with mydriatics as a consequence of concomitant iris atrophy |
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what causes INCOMPLETE argyll robertson pupil:
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1. diabetes
2. chronic alcoholism 3. encephalitis 4. multiple sclerosis 5. CNS degeneration disease 6. tumors of the MIDBRAIN |
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what is a tonic pupil
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1. abnormal pupillary constrictor mechanism
2. sphincter muscle contracts slowly to near stimulation 3. associated with loss of deep tendon reflexes (adie's syndrome) 4. results from damage to the ciliary ganglion |
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how do you diagnose a tonic pupil
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1. weak (0.1%) solution of pilocarpine instilled into the conjunctival sac causes a tonic pupil to constrict...NORMAL PUPILS ARE NOT AFFECTED
2. bilateral tonic pupils should raise a question of autonomic neuropathy |
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what causes horners syndrome
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lesion affecting the sympathetic nerve supply at any point along its pathway from the HYPOTHALAMUS
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horners syndrome symptoms
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1. slight unilateral ptosis
2. miosis of the affected eye 3. ipsilateral anhydrosis 4. heterchromia iridis 5. NO associated EOM defects |
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what are ocular flutter
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1. pathology of the fast phase system
2. back to back saccades 3. no intersaccadic interval |
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what are square wave jerks/square wave oscillations
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1. acquired defects
2. ~2-5 degrees 3. separated by normal intersaccadic intervals |
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what are some physiological nystagmuses
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1. Rebound nystagmus
2. Optokinetic 3. Vestibular 4. End-point (gaze evoked) R.O.V.E. |
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what is convergence-retraction pulses? what causes it?
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1. dorsal midbrain syndrome
2. asynchronous, opposed saccade on up gaze 3. not true convergence movements 4. saccadic disorder initiated by burst |
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vestibular nystagmus
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1. head rotations stimulate the labyrinths
2. excites the labyrinths on the side of rotation 3. inhibits the trailing labyrinth |
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optokinetic nystagmus
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1. the eyes track the moving scene with a slow eye movement
2. at a certain amp. or velocity of ocular displacement, the position of the eyes is reset by the fast phase 3. cont. stimulation leads to repetitive cycle 4. waveform is "saw tooth" 5. linear slow phase velocity 6. the motion of the visual scene causes the nystagmus and its mediated by retinal slip |
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end point nystagmus
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1. caused by looking into far lateral gaze
2. not always present (45%) 3. jerk nystagmus (fast phase towards lateral gaze and slow phase pulls eye back to center) 4. nystagmus diminishes over time |
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rebound nystagmus
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1. a reversal of EPN
2. dampen after short period of time 3. greater in the dark |
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what are the major congenital nystagmuses
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1. latent nystagmus
2. spasmus natans 3. congenital nystagmus |
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how freq is Latent Nystagmus seen in patients...what is it ALWAYS associated with?
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1. pure latent nystagmus is RARE
2. ALWAYS associated with strabismus |
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how is latent nystagmus enhanced? in what direction?
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1. enhanced when one eye in occluded
2. horizontal and conjugate 3. fast phase beats ALWAYS from the covered eye 4. slow phase velocity is decreasing or linear and decays over time 5. follows ALEXANDERS LAW |
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what is Alexander's Law
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1. nystagmus greatest when looking in direction of quick phase
2. patients turn their head to keep their viewing eye in an adducted position...nystagmus is minimal in this position |
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what is manifest latent nystagmus
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1. patient with latent nystagmus have a manifest component which can be seen clinically
2. when binocular function is lost, it is as if one eye was being covered |
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what are the characteristics of Spasmus nutans
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1. onset 4-18 months of age
2. resolves in middle infancy (3yrs) 3. has mostly a horizontal eye movements 4. intensity in each eye may be different 5. eye movements are disconjugate 6. head shaking (nodding) 7. torticollis |
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characteristics of congenital nystagmus
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1. involuntary eye movements
2. horizontal component 3. conjugate eye movements 4. onset in early infancy (0-4months) 5. can be idiopathic or inherited 6. no oscillopsia |
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what are the waveforms of congenital nystagmus
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1. accelerating slow phase
2. slow phase takes the eye off target, increasing speed over time 3. fast phase brings the eye back to the target |
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what are two basic types of waveforms
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1. pendular: velocity of the movement waxes and wanes
2. jerk: slow eye movement takes the eye off the target. the fast eye movement brings the eye back to the target |
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what is foveation time
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1. patient uses one part of the waveform to see
2. when nystagmus stops, after the eye has returned to target (from saccade) 3. and/or when eye movement is very slow |
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what is null position? where is it seen?
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1. orbital eye position where the nystagmus intensity is least
2. seen in congenital nystagmus |
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retinal point in fusional vergence
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1. images from both eyes must fall on corresponding retinal point for SINGLE image.
2. if not DIPLOPIA |
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visual confusion
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two different objects may be localized on corresponding retinal areas and appears to overlap or superimpose
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what are the stimuli to vergence movement
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1. binocular disparity
2. retinal blur 3. prospective cues based on proximity 4. looming 5. monocular cues derived from parallel motion |
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binocular disparity
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1. disparity between two image locations on the retinas that produce diplopia...which leads to fusional vergence
2. only static visual cues that is non pictorial |
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horopter
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1. set of pts. that fall on corresponding retinal pts. and locations for any given distance
2. single vision occurs for all points in the horopter and all points should appear equidistant from the observer |
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panum's fusional space
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region around the horopter where objects are seen as single even though the object points stimulate slightly off the corresponding retinal points
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where can the smallest range of disparity that can be fused centrally
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fovea
towards the periphery, ~30-40 min of arc can be fused at 12 deg from fovea |
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within panum's area of single binocular vision: what may cause diplopia
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horizontal retinal disparity of more than 10 min of arc
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requirement for stereopsis
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1. the retina must be stimulated by at least TWO objects within Panum's fusional space
2. object points must lie at a different distance from either the proximal or distal boundary of Panum's fusional space |
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what dimension does Fusional vergence work in? stereopsis?
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fusion: localize object ONLY in 2D plane (works for all fixation distances)
stereopsis: 3D plane (less effective as fixation distance increase) |
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two characteristics of accommodative vergence
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convergence
blur driven accommodation |
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proximal vergence
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1. when two objects are at different distances, the awareness of nearness of the closer obj. drives the proximal vergence sys.
2. refers to the change in vergence angle of the eyes caused solely by the relative apparent or perceived nearness of an object in the field |
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what is the fourth stimulus for vergence movement
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looming
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what is the interfixation movement range for eye movements during reading?
saccadic duration? avg saccade length? |
1. interfixation movement: 1-2deg (0.5-4 deg range) in angular extent
2. saccadic duration: 10-30msec 3. avg. saccade length: 8 characters (range: 1-18 characters) the percentage of total reading time taken up by actual eye movements themselves is no greater than 10% with an avg. of 7% |
