Midterm Flashcards by MECAELA AGUILLON

Conscious and purposeful fixation at an object of regard

Voluntary

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Involuntary fixation such as may occur in response to peripheral retinal stimulation

Reflex

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A rapid change of fixation from one point in the visual field to another

Saccadic/Jump Fixation

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Continued fixation of a moving object, implying a dynamic movement of the eye so as to keep the image of the object continuously on the fovea

Pursuit

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Series of rapid fixations associated with an attempt to survey quickly the details of a view subtending a relatively large area of the visual field

Scanning

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Continuous and fixed fixation of a non-moving object for a given period of time

Steady

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An imaginary eye located between the two physical eye which serves to represent the two retinas

Cyclopean eye/ binnoculus

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Retinal elements of the two eyes that share a common subjective visual direction are called

Corresponding retinal points

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Both the foveas have a common visual direction and the retinal elements nasal to the fovea in one eye correspond to the retinal elements temporal to the fovea of the other eye.

Normal Retinal Correspondence

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when the fovea of one eye has a common visual direction with an extrafoveal area in the other eye it is

ARC

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A condition in which the two foveas have different visual direction

ARC

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Process by which a single cortical image is perceived as a result of two separate ocular ones

Fusion

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States that fusion operates upon a psychological and cerebral level

Worth’s theory

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“Theory of Replacement”/ “Theory of Retinal Rivalry”

Verhoeff’s theory

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Based upon alternate shifting mosaic patterns from each ocular image, in which portions of ocular image of one eye combines with portions from the other, in varying pattern to form the final unified or single perceptual image

Verhoeff’s theory

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Maintains that single image is merely a projection of two identical images to the same perceptual position and that two ocular images are perceived as one because of their community location

Wall’s theory

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Superimposition or simultaneous (first degree fusion) of two ocular images (e.g., a bird in the cage) requires stimulation of retinal areas having common visual directions.

GRADE 1: Superimposition/Simultaneous Perception

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It is defined as sensory fusion in which the resultant percept is two-dimensional

GRADE 2: Flat Fusion

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Highest form of fusion
Ability to judge distant objects
Stereopsis (third degree fusion) is the binocular visual perception of threedimensional space based on retinal disparity.

GRADE 3: Stereopsis/Depth Perception

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It is the ability to distinguish disparity

Depth perception: stereopsis

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It is the depth perception for distance and is also used to imply the visual perception of three dimensional spaces.

Depth perception: stereopsis

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Requirements for Fusion

Equal or nearly equal visual acuity between two eyes
Monocular fixation of each eye
Normal sensorial relationship or normal retinal correspondence
Normal ocular motility
Representation of the crossed and uncrossed optic nerve fibers in the occipital cortex

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movement of the eye that happens automatically as a reaction to something.

Reflex eye movement

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Types of reflex eye movement

 Vestibulo-ocular reflex
 Optokinetic reflex
 Pupillary reflex
 Accommodative reflex
 Corneal reflex

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It produces eye movement in response to changes in head position This is an extraordinarily accurate reflex that allows the eyes to remain focused on a target when the head moves

VOR

It is seen when an individual follows a moving object with their eyes, which then moves out of the field of vision at which point their eye moves back to the position it was in when it first saw the object

Optokinetic reflex

is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retina of the pupil and the eye, thereby assisting in adaptation to various levels of lightness/darkness.

PLR

is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa), comprising coordinated changes in vergence, lens shape and pupil size (accommodation)

is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), or bright light, though could result from any peripheral stimulus.

Corneal reflex

Because of their small magnitude, eye movements during fixation are also referred to as

Micro or miniature eye movements

Categories of steady fixation

Ocular microtremor Ocular drifts Microsaccades

Tremor is present when the amplitude of fixation tremor is on the order of the diameter of the smallest cone.

Ocular micrometer

Compared to tremor, it is larger and slower. Amplitudes are 2 to 5 minutes. Direction of drifts is apparently uncorrelated between two eyes

Ocular drift

 Are kind of fixational eye movement. They are small, jerk-like involuntary eye movements, similar to miniature versions of voluntary saccades.  They typically occur during prolonged visual fixation  Range an amplitude from 1 to 23 seconds

Microsaccades

Saccades subtypes

 Volitional  Reflexive  Express saccades  Spontaneous  Quick phase of nystagmus

Exaggerated convergence is called

Cross eyed viewing

changing the focus of the eyes to look at an object at a different distance will automatically cause vergence and accommodation, sometimes known as the

accommodation-convergence reflex.

Classification of Vergence According to Maddox:

1.) Tonic Vergence 2.) Accommodative Vergence 3.) Fusional Vergence 4.) Proximal Vergence

Vergence due to normal extraocular muscle tone, with no accommodation and no stimulus to binocular fusion.

Tonic vergence

 blur-driven vergence  is that portion of the range of inward rotation of both eyes that occurs in response to an increase in optical power for focusing by the crystalline lens.  Minus lens stimulate accommodation and caused a vergence response in covered eye.

Accommodative vergence

Also known as:  disparity vergence  disparity-driven vergence  reflex vergence

Fusional vergence

vergence due to the awareness of a fixation object being near or far in the absence of disparity and of cues for accommodation. This includes also vergence that is due to a subject's intent to fixate an object in the dark.

Proximal vergence

sometimes also called voluntary vergence

Fusional vergence

is measured by bringing an object to the nose and observing when the patient sees double, or one eye deviates out.

NPC

The simultaneous occurring cyclorotation (torsional movement) of both eyes which is performed in opposite directions to obtain or maintain single binocular vision.

Cyclovergence

A condition in which the eyes do not point in the same direction.

Strabismus

A sensorimotor anomaly of binocular integration resulting in the failure to maintain bifoveal alignment manifesting in a divergent (exotropia), convergent (esotropia), or vertical deviation of nonfixating eye.

Strabismus

a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision. Due to the involuntary movement of the eye, it is often called "dancing eyes"

Nystagmus

the eye movement elicited by the tracking of a moving field.

Optokinetic nystagmus

caused by dysfunction of the vestibular part of the inner ear, the nerve, the vestibular nucleus within the brainstem, or parts of the cerebellum that transmit signals to the vestibular nucleus

Vestibular Nystagmus

Is defined as nystagmus with the fast phase beating in a downward direction

Downbeat

defined as nystagmus with the fast phase beating in an upward direction.

Upbeat nystagmus

 Nystagmus resulting from malfunction in the saccade and pursuit gaze systems is much less common than that due to fixation malfunction  is a rhythmic rotation of the eyes in which the 12 o'clock meridian of the limbus rotates, causing either intortion or extortion

Torsional nystagmus

Vergence dysfunctions

 Convergence Insufficiency  Convergence Excess  Divergence Insufficiency  Divergence  Basic Eso  Basic  Mixed

Causes: Lesions of the vestibulocerebellum and underlying medulla (eg, Arnold-Chiari malformation, microvascular disease with vertebrobasilar insufficiency, multiple sclerosis, Wernicke encephalopathy, encephalitis, lithium intoxication), Heat stroke

Downbeat

Causes: Medullary lesions, including perihypoglossal nuclei, the adjacent medial vestibular nucleus, and the nucleus intercalatus (structures important in gaze holding), Lesions of the anterior vermis of the cerebellum, Benign paroxysmal positional vertigo

Upbeat

Causes: Lateral medullary syndrome (Wallenberg syndrome)

Torsional nystagmus

is a multivectorial nystagmus (ie, horizontal, vertical, circular, elliptical) with an equal velocity in each direction that may reflect brainstem or cerebellar dysfunction.  Congenital or acquired  Causes: Demyelinating disease, Monocular or binocular visual deprivation, Oculopalatal myoclonus, Internuclear ophthalmoplegia, Brainstem or cerebellar dysfunction

Pendular nystagmus

a well-recognized finding in patients with a unilateral disease of the cerebral hemispheres, especially with large, posterior lesions.

Horizontal nystagmus

consists of elevation and intorsion of one eye and depression and extorsion of the fellow eye that alternates every half cycle.

Seesaw nystagmus

 eyes cannot be maintained at an eccentric orbital position and are pulled back toward primary position by the elastic forces of the orbital fascia.  Congenital nystagmus  Causes: Sedatives, tranquilizers, ethanol, and “Recreational drugs" can all cause nystagmus, Central (cerebellar or brainstem) lesion.

Gaze-evoked nystagmus

The presumed mechanism is disruption of the vestibulo-ocular tracts at the pontomedullary junction.

Periodic alternating nystagmus

 nystagmus in the abducting eye  abnormalities of the abducting eye in internuclear ophthalmoplegia reflect an adaptive process (Hering's law of equal innervation) that helps overcome the adduction weakness of the opposite eye.

Abducting Nystagmus of internuclear ophthalmoplegia

Subjective direction w/ the fovea when a given object is fixated

Principal visual direction

locus of all object points that are imaged on corresponding retinal elements at a given fixation distance.

Horopter

A.k.a. Theoretical horopter curve

Vieth-muller curve

This means that the distribution of the elements that correspond to each other is not the same in the nasal and temporal parts of the two retinas.

Empirical horopter curve

The region in front and back of the horopter in which single vision is present is known

Panum’s area of single binocular vision

refers to the direction of an object in space relative to one self, rather than the eyes.

Egocentric visual direction

Superimposed retinal images will be seen as being in alignment in the visual field, but at a different distance from the eye

Oculocentric visual direction

In which the angle of anomaly is equal to the objective angle of deviation. This indicates that the ARC fully corresponds to the strabismus.

Harmonius ARC

In which the angle of anomaly is less than the objective angle of deviation

Unharmonius ARC

When the angle of anomaly is greater than the objective angle of deviation

Paradoxical ARC

Assessment of relationship between the fovea of the fixing eye and the retinal area stimulated in the squinting eye.

Bagolinis striated glasses test Worth 4 dot test Red filter test Synaptophore

Assessment of the visual directions of the two foveas. Included in this are:

After image test Ophthalmoscopy

the hallmark of retinal correspondence

Single vision

the hallmark of retinal disparity

Diplopia

defined as the way that your left eye and your right eye view slightly different images.

Retinal disparity

is the basic instrument used for measuring or training binocular vision, for stimulating vision in an amblyopic eye and for increasing fusion of the eyes.

Major amblyoscope

Diagnostic uses of major amblyoscope

1. Measurement of the objective and subjective angle of deviation. 2. Measurement of angle kappa. 3. Measurement of primary and secondary deviation. 4. Measurement of deviation in cardinal directions of gaze. 5. Estimation of status of binocular vision.

Therapeutic uses

1. Suppression. 2. ARC. 3. Eccentric fixation (only in models that have special attachments with Haidinger Brushes). 4. Accommodative esotropia (dissociation training). 5. Heterophorias and intermittent heterotropias (improvement of fusional amplitudes)

Midterm Flashcards

(81 cards)