Exam 7 - Second Set (Eye slide 14 - Image slide 50) Flashcards by James Ozorkiewicz

Six extrinsic muscles move each eye:

Superior rectus
Inferior rectus 
Lateral rectus 
Medial rectus 
Superior oblique 
Inferior oblique

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The extrinsic muscles of the eye are innervated by some combination of cranial nerves

III, IV, or VI

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The ___ eye muscles move the eyeball laterally, medially, superiorly, and inferiorly

extrinsic

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___ muscles move the eye in a plane (for the most part, anyway—the superior and inferior rectus are not on the exact midline)

Rectus

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The ____ muscles preserve rotational stability of the eyeball

oblique

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There are eight cardinal directions of eye movement. What are they?

superior, inferior, nasal, temporal, up & in, up & out, down & in, and down & out, shown here for the right eye

slide 17

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Six of the eight cardinal directions of eye movement are associated with a single extrinsic muscle. These six are termed ____. Only the two remaining directions of eye movement (ie. the non-cardinal directions) are caused by two muscles acting in concert.

cardinal directions of gaze

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The six directions that involve a single muscle are circled (the cardinal directions of gaze), along with the muscle that moves the eye in that direction from the starting point of looking straight ahead. (Right eye illustrated)

Slide 19

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Cranial nerve __ is associated with multiple directions

III

Slide 20

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The following “formula” may be useful…

for eye muscle innervation

LR6 (SO4) 3

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LR6 = lateral rectus is innervated by?

SO4 = superior oblique is innervated by?

Subscript 3 = all other muscles are innervated by?

cranial nerve 6 (CN VI)

cranial nerve 4 (CN IV)

cranial nerve 3 (CN III)

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Smoothly and uniformly moving the eye from the starting position of looking straight ahead to the final position of one of the cardinal directions of gaze is not an easy achievement. In practice, moving the eye generally involves more than one extrinsic muscle, and therefore frequently, more than one nerve. These combined actions need to be negated in order to properly assess the function of individual muscles and nerves.

Ok cool

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In order to eliminate the effects of combined action on the eye by two extrinsic muscles, and their associated cranial nerves, the action of muscles (and associated nerves) must be isolated.

Alright we get it

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When the eye is fully abducted (away from the nose), only the ____ muscles can elevate and depress the eye, respectively.

superior and inferior rectus.

This is purely a mechanical property caused by the axis of the eye lining up perpendicular to the superior/inferior rectus muscles.

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When the eye is fully adducted (toward the nose), only the superior and inferior oblique muscles can ____.

depress and elevate the eye.

In this case, the superior oblique depresses the eye, and the inferior oblique elevates the eye

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In this course whenever you see an “H” superimposed over the eye, the situation refers to a patient exam.

The directional arrows may still be retained in illustrations that have the “H”

Slide 24

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During a patient exam, these isolating effects are applied by having the patient fully ___ the eye then look up and down. Next, fully adduct the eye and look up and down. This results in an “H” shaped pattern of eye movement. The six directions encompass the cardinal directions of gaze.

abduct

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Eliminating combined action… But there is a slight complication resulting from this isolation mechanism. Recall that starting from the position of looking straight ahead, the inferior oblique is responsible for moving the eye up and out. Eye placement is then in the “up & out” quadrant due to action of the ____ (innervated by cranial nerve III).

inferior oblique

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Eliminating combined action… But during a patient exam when the eye is fully abducted (by the lateral rectus), the mechanics of the situation are such that the ____ now elevates the eye. Eye placement is then in the “up & out” quadrant due to action of the superior rectus (still innervated by cranial nerve III).

superior rectus

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Eliminating combined action… Starting with the eye looking straight ahead, the ___ is responsible for moving the eye down and out. At the end of the action, the eye is in the “down & out” quadrant due to action of the ____

superior oblique

(innervated by CN IV).

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Eliminating combined action…
With the eye fully abducted (the bar of the “H”) during an exam, the ____ depresses the eye. At the end of this action, the eye is in the “down & out” quadrant due to action of the ___

inferior rectus (innervated by CN III).

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Eliminating combined action… None of this changes the formula ___, which relates to the cranial nerves that supply particular extrinsic eye muscles. That relationship does not change

LR6 (SO4) 3

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Eliminating combined action… What does change in some instances is the muscle that achieves the final result of moving the eye up or down when comparing the cardinal directions of gaze versus the cardinal directions of eye movement. And since that muscle may have changed, the ___ associated with that resultant action may also have changed.

nerve

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Brace yourself and look at slide 28

What’s even going on there?

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Much of the time, the concern is not so much with the muscles involved in moving the eye, but rather with the ___ involved. For that reason, we will spend some time on the __.

nerves

The cranial nerve associated with each of the cardinal directions of gaze is shown for the right eye. Cardinal directions of gaze ___ actions of individual extrinsic muscles of the eye, and their cranial nerves, enabling a determination of damage to the muscle or cranial nerve.

isolate slide 30, 31

Although CN III (oculomotor) innervates the inferior rectus which causes movement in this direction from the starting point of looking straight ahead, with the eye fully adducted the only muscle that can depress the eye is the

superior oblique, which is innervated by CN IV (trochlear)

Although CN IV (trochlear) innervates the superior oblique which causes movement in this direction from the starting point of looking straight ahead, with the eye fully ___ the only muscle that can depress the eye is the inferior rectus, which is innervated by CN III (oculomotor)

abducted

The details of why a given muscle exhibits the particular action it has, or why a certain eye movement is associated with a specified cranial nerve are frequently of no concern in a clinical setting, as illustrated by this extract from Bates

Slide 34

An imbalance in the extrinsic eye muscles resulting in the misalignment of one eye so that its line of vision is not parallel with that of the other eye (cross-eyes).

Strabismus

Both eyes are not pointed at the same object at the same time

Strabismus

In strabismus, to compensate, the normal and deviant eyes may alternate in focusing on objects. In other cases, only the controllable eye is used, and the brain begins to disregard inputs from the ___, which then becomes functionally blind

deviant eye

Can strabismus be outgrown?

Strabismus treatment?

Less severe cases may be treated with eye exercises to strengthen the weak muscles, or by temporarily placing a patch on the stronger eye thereby forcing the child to use the weaker eye When the above do not correct the situation, surgery on the eye muscles is needed

Layman's term for strabismus?

Lazy eye

rapid involuntary movement of the eyeballs May be inherited, idiopathic, or caused by a disease of the central nervous system

Nystagmus a sign, not a disease There are a number of types of nystagmus, and a number of causes

occurs much less frequently than horizontal nystagmus

Vertical nystagmus

complex of eye movements that occurs during and immediately after rotational motion

Vestibular nystagmus

In police work, testing for ___ is one of a battery of field sobriety tests used by officers in the field to determine whether a suspect is driving under the influence of alcohol

horizontal gaze nystagmus

The eye consists | of three layers:

Fibrous tunic Vascular tunic Retina

Is the superficia coat of the eyeball Is avascular

Fibrous tunic

Fibrous tunic consists of?

Cornea | Sclera

Transparent coat that covers the iris

Cornea

Is curved, so it focuses light

Cornea

The “white” of the eye

Sclera

Dense connective tissue, mostly collagen and fibroblasts

Sclera

Covers the entire eyeball except the cornea Gives shape to eyeball, makes it more rigid, and protects inner parts of the eye

Sclera

The middle layer of the eye

Vascular tunic

Vascular tunic composed of?

Choroid Ciliary body Iris

Highly vascular Lines most of the internal surface of the sclera

Choroid

Provides nutrients to the posterior surface of the sclera

Choroid

Ciliary body Consists of:

Ciliary processes Ciliary muscle

Protrusions or folds on the internal surface of the ciliary body Contains blood capillaries that secrete aqueous humor

Ciliary processes

A circular band of smooth muscle that alters the shape of the lens When it contracts it reduces tension on suspensory ligaments that hold the lens, thereby allowing it to assume a more spherical shape (for closer vision)

Ciliary muscle

the colored portion of the eyeball

Iris

It is attached at its outer margin to the ciliary processes

Iris

Iris regulates the amount of light entering the eye through the pupil, via autonomic reflexes

autonomic

____ neurons stimulate the sphincter pupillae (circular muscles) contract to cause a decrease in the size of the pupil (constriction)

Parasympathetic

Sympathetic neurons stimulate the dilator pupillae (radial muscles) of the iris to contract, causing an

increase in the size of the pupil (dilation)

The third, and inner coat of eyeball

Retina

The retina lines the ___ ¾ of the eyeball

posterior

It is the beginning of | the visual pathway

Retina

The surface of the retina is the only place in the body where ___ can be viewed directly (ophthalmoscope) and examined for pathological changes

blood vessels

is the site where the optic nerve exits the eyeball

optic disc

The ___ retinal artery and ___ retinal vein are adjacent to the optic disc

central

The pigmented layer of the retina is a sheet of ___ coated epithelial cells. It absorbs stray light, thereby preventing reflection and scattering

melanin-

The neural layer of the retina is an outgrowth of the brain It has three distinct layers of retinal neurons:

Photoreceptor layer Bipolar layer Ganglion layer

The neural layer of the retina also has two zones—a zone between each layer:

Outer synaptic layer | Inner synaptic layer

``` Two types of photoreceptors transduce light rays into receptor potentials: ```

Rods Cones

have a low light threshold and enable seeing only shades of gray

Rods

have a higher light threshold and provide color vision

Cones

in the exact center of the visual axis of the eye of the posterior portion of the retina

macula lutea

a small depression in the center of the macula lutea

The central fovea

The ____ contains no rods or cones | An image that strikes the ___ can not be seen

optic disc It is therefore called the blind spot

degenerative disorder of the retina and pigmented layer that may begin to show effects in persons 50 years of age and older Abnormalities occur in the region of the macula lutea

Age-related macular disease Also called macular degeneration Victims of advanced AMD retain peripheral vision but lose the ability to see straight ahead

Age-related macular disease two forms?

“Dry” in which central vision gradually diminishes because the pigmented layer atrophies and degenerates. There is no effective treatment for this form. “Wet” form in which new blood vessels form in the choroid and leak plasma or blood under the retina. Treatment for this form is laser surgery to destroy leaking blood vessels

behind the pupil and iris

lens

consists of proteins called crystallins, which are arranged like the layers of an onion, and enclosed in a capsule

lens

It is transparent (normally), and lacks blood vessels | It is the variably refractive medium of the eye

lens

Loss of transparency of the lens is termed a

cataract The lens becomes cloudy due to changes in the structure of lens proteins

When cataracts occur they are generally associated with aging, but they may be due to injury, excessive exposure to UV light, some medications (long-term steroid use), disease (diabetes), chemicals (glutaraldehyde, osmium tetroxide), and an increased risk due to ___

risk due to smoking Surgical removal of the affected lens and implantation of a new artificial lens usually restores sight

The lens divides the eye into two cavities:

Anterior cavity | Vitreous chamber

The anterior cavity consists of two chambers:

Anterior chamber, between the cornea and iris Posterior chamber, behind the iris, and in front of the lens

Both chambers are filled with aqueous humor

Anterior chamber, between the cornea and iris Posterior chamber, behind the iris, and in front of the lens

Major contributor of intraocular pressure Manufactured by filtration of blood by capillaries of the ciliary processes

Aqueous humor

Aqueous humor Flows between the iris and the lens, through the pupil, into the anterior chamber From the anterior chamber it drains into the ____, which is at the junction of the sclera and cornea. Then returns to the blood.

scleral venous sinus (canal of Schlemm) Normally replaced about every 90 minutes

high intraocular pressure When unchecked, ____ damages the optic nerve and retina, resulting in blindness

glaucoma

Glaucoma is usually caused by impaired drainage of aqueous humor The canal of Schlemm is at the vertex of the angle formed by the intersection of the cornea and the iris, called the

ocular angle

In primary closed angle glaucoma, pressure from the ____ chamber pushes the iris forward, closing the ocular angle and preventing drainage of aqueous humor

posterior

In primary open angle glaucoma the ocular angle remains open, but abnormalities in the trabecular meshwork associated with ___ impede the outflow of aqueous humor

Schlemm’s canal

Glaucoma is treated with cholinergic agonists (cholinomimetics), which constrict the pupil, ___ the ciliary muscles, and decrease intraocular pressure

contract

In ___ angle glaucoma, pupillary constriction lowers intraocular pressure by pulling the iris away from the canal of Schlemm and opening the angle In ___ angle glaucoma, contraction of the ciliary muscle stretches the trabecular meshwork thereby opening its tubules

closed open

The larger of the two cavities

Vitreous chamber

Jellylike substance Contributes to intraocular pressure Holds retina flush against the choroid

vitreous body of vitreous chamber

Contains phagocytic cells that remove debris, thereby providing for unobstructed vision Formed during embryonic development, and not replaced thereafter

vitreous body of vitreous chamber

Hyaloid canal is the remnant of the ___ artery

hyaloid

vitreous body of vitreous chamber composed mostly of?

Water Hyaluronic acid Collagen

Vitreous body: Attachments to the retina, which are important in understanding retinal tears and retinal detachment, are

Just behind the ora serrata At the optic disk

the serrated junction between the retina and the ciliary body.

ora serrata

This junction marks the transition from the simple non-photosensitive area of the retina to the complex, multi-layered photosensitive region.

ora serrata

The ___ attaches anteriorly just behind the ora serrata.

vitreous body

Loss of transparency of the lens due to changes in the structure of lens proteins typically due to aging, injury, excessive exposure to UV light, chemicals, or medications? Abnormally high intraocular pressure due to buildup of aqueous humor within the anterior cavity?

Cataract. Glaucoma

inflammation of the eyelid? Inflammation of the conjunctiva due to bacteria (contagious) or irritants (not contagious) ?

Blepharitis Conjunctivitis (pinkeye).

A scratch on the surface of the cornea? Procedure in which a donor cornea replaces a removed defective cornea?

Corneal abrasion. Corneal transplant.

Degenerative disease of the retina due to diabetes mellitus, in which blood vessels in the retina are damaged or new ones grow and interfere with vision? Turning outward of the eyes ? An inflammation or infection of the cornea?

Diabetic retinopathy. Exotropia. Keratitis.

Constriction of the pupil ? Dilation of the pupil? Abnormal visual intolerance to light ?

Miosis. Mydriasis. Photophobia.

Falling or drooping of the eyelid (or slippage of any organ below its normal position) ? A tumor arising from immature retinal cells; accounts for 2% of childhood cancers?

Ptosis. Retinoblastoma.

An area of reduced or lost vision in the visual field? Instrument for measuring intraocular pressure?

Scotoma. Tonometer.

A serious form of conjunctivitis, and the greatest single cause of blindness in the world, caused by the bacterium Chlamydia trachomatis; produces an excessive growth of subconjunctival tissue and invasion of blood vessels into the cornea, progressing until the entire cornea is opaque

Trachoma.

Exam 7 - Second Set (Eye slide 14 - Image slide 50) Flashcards

(109 cards)