Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates,

rodents Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...

flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight ...

, fish,

cats The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of t ...

crabs Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting " tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all th ...

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlef ...

) to fixate, inspect and

track Track or Tracks may refer to: Routes or imprints * Ancient trackway, any track or trail whose origin is lost in antiquity * Animal track, imprints left on surfaces that an animal walks across * Desire path, a line worn by people taking the shorte ...

visual objects of interests. A special type of eye movement, rapid eye movement, occurs during REM sleep. The eyes are the visual organs of the human body, and move using a system of six muscles. The retina, a specialised type of tissue containing photoreceptors, senses light. These specialised cells convert light into electrochemical signals. These signals travel along the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from ...

fibers to the brain, where they are interpreted as vision in the visual cortex. Primates and many other vertebrates use three types of voluntary eye movement to track objects of interest: smooth pursuit, vergence shifts and

saccade A saccade ( , French for ''jerk'') is a quick, simultaneous movement of both eyes between two or more phases of fixation in the same direction.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishi ...

s. These types of movements appear to be initiated by a small cortical region in the brain's frontal lobe. This is corroborated by removal of the frontal lobe. In this case, the reflexes (such as reflex shifting the eyes to a moving light) are intact, though the voluntary control is obliterated."Sensory Reception: Human Vision: Structure and function of the Human Eye" Encyclopædia Britannica, 1987

Anatomy

Muscles

Six

extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the oth ...

facilitate eye movement. These muscles arise from the

common tendinous ring The common tendinous ring, also known as the annulus of Zinn, or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the common origin of the four recti muscles of the group of ex ...

(annulus of Zinn) in the orbit (eye cavity), and attach to the

eyeball Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. The six muscles are the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...

, medial, inferior and

superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places *Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lake ...

recti muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the oth ...

, and the inferior and

superior oblique The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit (i.e. from beside the nose) which abducts, depresses and internally rotates the eye. It is the only extraocular musc ...

muscles. The muscles, when contracting, cause movement of the eyeball, by pulling the eyeball towards the muscle. For example, the

lateral rectus Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...

is on the

side of the eyeball. When it contracts, the eyeball moves so that the pupil looks outwards. The

medial rectus The medial rectus muscle is a muscle in the orbit near the eye. It is one of the extraocular muscles. It originates from the common tendinous ring, and inserts into the anteromedial surface of the eye. It is supplied by the inferior division of th ...

causes the eyeball to look inwards; the

inferior rectus Inferior may refer to: * Inferiority complex * An anatomical term of location * Inferior angle of the scapula, in the human skeleton * ''Inferior'' (book), by Angela Saini * '' The Inferior'', a 2007 novel by Peadar Ó Guilín See also *Junior ( ...

downwards and the

superior rectus The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve (III). In the primary position (looking straight ahead), its primary function is elevation ...

upwards. The superior oblique muscle and inferior oblique muscle attach at angles to the eyeball. Extraocular muscle actions and innervation

Three antagonistic pairs of muscles control eye movement: the lateral and medial recti muscles, the superior and inferior recti muscles, and the superior and inferior oblique muscles. These muscles are responsible for movement of the eye along three different axes: horizontal, either toward the nose (adduction) or away from the nose (abduction); vertical, either elevation or depression; and torsional, movements that bring the top of the eye toward the nose (intorsion) or away from the nose (extorsion). Horizontal movement is controlled entirely by the medial and lateral recti muscles; the medial rectus muscle is responsible for adduction, the lateral rectus muscle for abduction. Vertical movement requires the coordinated action of the superior and inferior recti muscles, as well as the oblique muscles. The relative contribution of the recti and oblique groups depends on the horizontal position of the eye. In the primary position (eyes straight ahead), both of these groups contribute to vertical movement. Elevation is due to the action of the superior rectus and inferior oblique muscles, while depression is due to the action of the inferior rectus and superior oblique muscles. When the eye is abducted, the recti muscles are the prime vertical movers. Elevation is due to the action of the superior rectus, and depression is due to the action of the inferior rectus. When the eye is adducted, the oblique muscles are the prime vertical movers. Elevation is due to the action of the inferior oblique muscle, while depression is due to the action of the superior oblique muscle. The oblique muscles are also primarily responsible for torsional movement. The muscles are supplied by the

oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...

, with the exception of the superior oblique, which is supplied by the trochlear nerve, and the lateral rectus, supplied by the

abducens nerve The abducens nerve or abducent nerve, also known as the sixth cranial nerve, cranial nerve VI, or simply CN VI, is a cranial nerve in humans and various other animals that controls the movement of the lateral rectus muscle, one of the extraocula ...

Neuroanatomy

The brain exerts ultimate control over both voluntary and involuntary eye movement. Three

cranial nerve Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

s carry signals from the brain to control the extraocular muscles. These are the

, which controls the majority of the muscles, the trochlear nerve, which controls the superior oblique muscle, and the

, which controls the

muscle. In addition to the movement of muscles, numerous areas in the brain contribute to involuntary and voluntary eye movement. These include providing the conscious perception of vision, as well as areas that facilitate tracking. * Brain **

Cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...

*** Frontal lobe – frontal eye fields (FEF),

medial eye fields Medial eye fields are areas in the frontal lobe of the primate brain that play a role in visually guided eye movement. Most neuroscientists refer to this area as the supplementary eye fields. Eye fields are divided into two hemispheres regulated by ...

(MEF), supplementary eye fields (SEF), dorsomedial frontal cortex (DMFC) *** Parietal lobe – Lateral intraparietal cortex (LIP), middle temporal area (MT), medial superior temporal area (MST) ***

Occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...

**** Visual cortex **

Cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebe ...

Midbrain The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', "m ...

Pretectal area In neuroanatomy, the pretectal area, or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system. Through reciprocal bilateral projections from the retina, it is involved primarily in mediati ...

– Pretectal nuclei ** Superior colliculus (SC) ** Premotor nuclei in the reticular formation (PMN) *** riMLF ** III, IV

cranial nerve nuclei A cranial nerve nucleus is a collection of neurons (gray matter) in the brain stem that is associated with one or more of the cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesio ...

* Pons **

Paramedian pontine reticular formation The paramedian pontine reticular formation, also known as PPRF or paraabducens nucleus, is part of the pontine reticular formation, a brain region without clearly defined borders in the center of the pons. It is involved in the coordination of eye ...

(PMRF) **

Nucleus prepositus hypoglossi The nucleus prepositus (also nucleus prepositus hypoglossi), located in the caudal pons and upper medulla oblongata, contributes to several aspects of gaze control including the horizontal gaze holding system. It functions as a neural integrato ...

** Vestibular nuclei ** VI cranial nerve nuclei * Medial longitudinal fasciculus

Physiology

Eye movement can be classified according to two systems: * the involvement of one or both eyes; involving one eye they may be classified as

duction A duction is an eye movement involving only one eye. There are generally six possible movements depending upon the eye's axis of rotation: # Abduction refers to the outward movement of an eye. #Adduction refers to the inward movement of an eye #Supr ...

, and both eyes either

version Version may refer to: Computing * Software version, a set of numbers that identify a unique evolution of a computer program * VERSION (CONFIG.SYS directive), a configuration directive in FreeDOS Music * Cover version * Dub version * Remix * '' ...

, if moving in the same direction, or vergence, if moving in opposite directions.Kanski, JJ. ''Clinical Ophthalmology: A Systematic Approach.'' Boston:Butterworth-Heinemann;1989. * fixational, ''gaze-stabilizing'', or ''gaze-shifting''. Gaze-stabilising movement may include the vestibulo-ocular reflex and

optokinetic reflex The optokinetic response is a combination of a slow-phase and fast-phase eye movements. It is seen when an individual tracks (pursuit movement) a moving object with their eyes, which then moves out of the field of vision, a point at which their ...

, and gaze-shifting mechanisms as

s and pursuit movements. ''Vergence movement'' or

convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen * "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that united the four Wei ...

is the movement of both eyes to make sure that the image of the object being looked at falls on the corresponding spot on both retinas. This type of movement helps in the depth perception of objectsCarlson and Heth (2010). Psychology the Science of Behaviour 4e. Pearson Education Canada. Page 140 ''Pursuit movement'' or smooth pursuit is the movement the eyes make while tracking an object's movement, so that its moving image can remain maintained on fovea.

Saccades

The eyes are never completely at rest: they make frequent fixational eye movement even when fixated at one point. The reason for this movement is related to the photoreceptors and the ganglion cells. It appears that a constant visual stimulus can make the photoreceptors or the ganglion cells become unresponsive; on the other hand a changing stimulus will not. So the eye movement constantly changes the stimuli that fall on the photoreceptors and the ganglion cells, making the image clearer.

Saccade A saccade ( , French for ''jerk'') is a quick, simultaneous movement of both eyes between two or more phases of fixation in the same direction.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishi ...

s are the rapid movement of eyes that is used while scanning a visual scene. In our subjective impression, the eyes do not move smoothly across the printed page during reading. Instead, they make short and rapid movements called saccades. During each saccade the eyes move as fast as they can and the speed cannot be consciously controlled in between the fixations. Each movement is worth a few minutes of arc, at regular intervals about three to four per second. One of the main uses for saccades is to scan a greater area with the high-resolution fovea of the eye. Research conducted by the

University of South Australia The University of South Australia (UniSA) is a public research university in the Australian state of South Australia. It is a founding member of the Australian Technology Network of universities, and is the largest university in South Austral ...

in partnership with the University of Stuttgart has revealed the relationship between eye moment and

personality traits In psychology, trait theory (also called dispositional theory) is an approach to the study of human personality. Trait theorists are primarily interested in the measurement of ''traits'', which can be defined as habitual patterns of behaviour, ...

that AI can read.

Vestibulo-ocular system

The visual system in the brain is too slow to process that information if the images are slipping across the retina at more than a few degrees per second. Thus, to be able to see while we are moving, the brain must compensate for the motion of the head by turning the eyes. Another specialisation of visual system in many vertebrate animals is the development of a small area of the retina with a very high visual acuity. This area is called the fovea, and covers about 2 degrees of visual angle in people. To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. Eye movement is thus very important for visual perception, and any failure can lead to serious visual disabilities. To see a quick demonstration of this fact, try the following experiment: hold your hand up, about one foot (30 cm) in front of your nose. Keep your head still, and shake your hand from side to side, slowly at first, and then faster and faster. At first you will be able to see your fingers quite clearly. But as the frequency of shaking passes about 1 Hz, the fingers will become a blur. Now, keep your hand still, and shake your head (up and down or left and right). No matter how fast you shake your head, the image of your fingers remains clear. This demonstrates that the brain can move the eyes opposite to head motion much better than it can follow, or pursue, a hand movement. When your pursuit system fails to keep up with the moving hand, images slip on the retina and you see a blurred hand. The brain must point both eyes accurately enough that the object of regard falls on corresponding points of the two retinas to avoid the perception of double vision. In most

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

(humans, mammals, reptiles, birds), the movement of different body parts is controlled by

striated muscles Striations means a series of ridges, furrows or linear marks, and is used in several ways: * Glacial striation * Striation (fatigue), in material * Striation (geology), a ''striation'' as a result of a geological fault * Striation Valley, in Anta ...

acting around joints. The movement of the eye is slightly different in that the eyes are not rigidly attached to anything, but are held in the orbit by six

. *

Hering's law of equal innervation Hering's law of equal innervation is used to explain the conjugacy of saccadic eye movement in stereoptic animals. The law proposes that conjugacy of saccades is due to innate connections in which the eye muscles responsible for each eye's movemen ...

Sherrington's law of reciprocal innervation René Descartes (1596–1650) was one of the first to conceive a model of reciprocal innervation (in 1626) as the principle that provides for the control of agonist and antagonist muscles. Reciprocal innervation describes skeletal muscles as exi ...

Reading

When reading, the eye moves continuously along a line of text, but makes short rapid movements (saccades) intermingled with short stops (fixations). There is considerable variability in fixations (the point at which a saccade jumps to) and saccades between readers and even for the same person reading a single passage of text.

Music reading

Eye movement in music reading is the scanning of a musical score by a musician's eyes. This usually occurs as the music is read during performance, although musicians sometimes scan music silently to study it, and sometimes perform from memory without score. Eye movement in music reading may at first appear to be similar to that in language reading, since in both activities the eyes move over the page in fixations and saccades, picking up and processing coded meanings. However, music is nonlinguistic and involves a strict and continuous time constraint on an output that is generated by a continuous stream of coded instructions.

Scene viewing

Eye movement in scene viewing refers to the visual processing of information presented in scenes. A core aspect of studies in this area is the division of eye movements into the rapid movement of the eyes ( saccades), and the focus of the eyes on a point (fixations). Several factors can influence eye movement in scene viewing, including the task and knowledge of the viewer (top-down factors), and the properties of the image being viewed (bottom-up factors). Typically, when presented with a scene, viewers demonstrate short fixation durations and long saccade amplitudes in the earlier phases of viewing an image. This is followed by longer fixations and shorter saccades in the latter phases of scene viewing processing. It has also been found that eye movement behaviour in scene viewing differs with levels of

cognitive development Cognitive development is a field of study in neuroscience and psychology focusing on a child's development in terms of information processing, conceptual resources, perceptual skill, language learning, and other aspects of the developed adult bra ...

- fixation durations are thought to shorten and saccade amplitudes lengthen with an increase in age.

Spatial variation

Where eye movements fixate is affected by both bottom-up and top-down factors. Even an initial glimpse of a scene has an influence on subsequent eye movements. In bottom-up factors, the local contrast or prominence of features in an image, such as a large contrast in luminance or a greater density of edges, can affect the guidance of eye movements. However, the top-down factors of scenes have a greater impact in where eyes fixate. Areas containing more meaningful features, or areas where colour aids the discrimination of objects, can influence eye movements. Images which are related to previous images shown can also have an effect. Eye movements can also be guided towards items when they are heard verbally at the same time as seeing them. Cross-culturally, it has been found that Westerners have an inclination to concentrate on focal objects in a scene, whereas East Asians attend more to contextual information.

Temporal variation

Average fixation durations last for about 330 ms, although there is a large variability in this approximation. This variability is mostly due to the properties of an image and in the task being carried out, which impact both bottom-up and top-down processing. The masking of an image and other degradations, such as a decrease in luminance, during fixations (factors which affect bottom-up processing), have been found to increase the length of fixation durations. However, an enhancement of the image with these factors also increases fixation durations. Factors which affect top-down processing (e.g. blurring) have been found to both increase and decrease fixation durations.

Disorders

Symptoms

* Patients with eye movement disorders may report diplopia,

nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...

, poor visual acuity or cosmetic blemish from squint of the eyes.

Cause

* Innervational ** Supranuclear ** Nuclear ** Nerve ** Synapse * Muscle anomalies ** Maldevelopment (e.g. Hypertrophy, atrophy/dystrophy) ** Malinsertion ** Scarring secondary to alignment surgery ** Muscle diseases (e.g. Myasthenia gravis) * Orbital anomalies ** Tumor (e.g.

rhabdomyosarcoma Rhabdomyosarcoma (RMS) is a highly aggressive form of cancer that develops from mesenchymal cells that have failed to fully differentiate into myocytes of skeletal muscle. Cells of the tumor are identified as rhabdomyoblasts. There are four sub ...

) ** Excess fat behind globe (e.g. thyroid conditions) ** Bone fracture ** Check ligament (e.g. Brown's syndrome, or Superior tendon sheath syndrome)

Selected disorders

Congenital fourth nerve palsy Congenital fourth nerve palsy is a condition present at birth characterized by a vertical misalignment of the eyes due to a weakness or paralysis of the superior oblique muscle. Other names for fourth nerve palsy include superior oblique palsy an ...

Duane syndrome Duane syndrome is a congenital rare type of strabismus most commonly characterized by the inability of the eye to move outward. The syndrome was first described by ophthalmologists Jakob Stilling (1887) and Siegmund Türk (1896), and subsequentl ...

* Internuclear ophthalmoplegia *

Nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...

Ophthalmoparesis Ophthalmoparesis refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic, ophthalmologic, and endocrine disease. Internal ...

Opsoclonus Opsoclonus refers to uncontrolled, irregular, and nonrhythmic eye movement. Opsoclonus consists of rapid, involuntary, multivectorial (horizontal and vertical), unpredictable, conjugate fast eye movements without inter- saccadic intervals. It is ...

* Sixth (abducent) nerve palsy

Vision therapy

In psychotherapy

Terminology

The following terms may be used to describe eye movement: * ''Incyclotorsion'' is a term applied to the inward, torsional (rotational) movement of the eye, mediated by the

muscle of the eye. The superior oblique muscle is innervated by cranial nerve IV ( trochlear nerve). Incyclotorsion may also be used to describe one part of the condition of the eye when a patient has an

oculomotor nerve palsy Oculomotor nerve palsy or oculomotor neuropathy is an eye condition resulting from damage to the third cranial nerve or a branch thereof. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements (fou ...

. The

(cranial nerve III) supplies the

inferior oblique The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit. The inferior oblique is one of the extraocular muscles, and is attached to the maxillary bone (origin) and ...

muscle (along with four other eye muscles – superior rectus, medial rectus, inferior rectus and the striated muscle of levator palpebrae superioris), and when this muscle is non-functional (as in oculomotor palsy) the eye ''incyclotorts''; i.e. twists/rotates inward. * ''Excyclotorsion'' is a term applied to the outward, torsional (rotational) movement of the eye, mediated by the

muscle of the eye. The inferior oblique muscle is innervated by cranial nerve III (

). Excyclotorsion may also be used to describe the condition or state of the eye when a patient has a cranial nerve IV ( trochlear nerve)

palsy Palsy is a medical term which refers to various types of paralysisDan Agin, ''More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children;; (2009), p. 172. or paresis, often accompanied by weakness and ...

. The trochlear nerve supplies the superior oblique muscle, and when this muscle is non-functional (as in trochlear palsy) the eye ''excyclotorts''; i.e. twists/rotates outward. This excyclotorsion may be corrected through surgery using the Harada-Ito procedure.1. http://www.utdol.com/online/content/topic.do?topicKey=neuro_op/2892&selectedTitle=1~150&source=search_result * A ''version'' is an eye movement involving both eyes moving synchronously and symmetrically in the same direction. Examples include: # Dextroversion / right gaze # Laevoversion / left gaze # Sursumversion / elevation / up gaze # Deorsumversion / depression / down gaze # Dextroelevation / gaze up and right # Dextrodepression / gaze down and right # Laevoelevation / gaze up and left # Laevodepression / gaze down and left # Dextrocycloversion – top of the eye rotates to the right # Laevocycloversion – top of the eye rotates to the left

References

External links

eMedicine – Extraocular Muscles, Actions

''Oculomotor Control – Nystagmus and Dizziness''
Department of Otolaryngology – Queen's University at Kingston, Canada

Software system for simulating eye motility disorders and their surgical correction

which shows changes in eye movements for any given muscle or nerve impairment. {{DEFAULTSORT:Eye Movement (Sensory) Eye