Bcsc/friedmann Peds Ophtho Test Deck

Front 1

At birth, the diameter of the eye is X that of adult eye

Back 1

66%

The eye enlarges until 2 years, and then further growth in puberty. Axial length increases from 15-17 in the newborn to 23-24 in the adult. It increases three phases: 4mm by 6 months, then 1mm from 2-5years old, 1mm from 5-13 years old.

Ophthalmologists should be familiar with the normal growth and development of the pediatric eye since departures from the norm may represent pathology.

Front 2

test

Back 2

test

Front 3

test

Back 3

test

Front 4

Where does the muscle cone lie relative to the equator of the globe? What is it made out of? Does it extend to the orbital apex?

Back 4

The muscle cone lies posterior to the equator. It consists of the extraocular muscles, the
extraocular muscle sheaths, and the intermuscular membrane. Whether the muscle cone
extends to the orbital apex is controversial.

Front 5

basic strab terminology

Back 5

skipped - see pg 9, 10 peds bcsc if unfamiliar with eso/exo tropi/phoria etc

Front 6

phoria

Back 6

deviation that is ONLY brought on by disrupting normal binocular vision

Front 7

intermittent tropia

Back 7

sometimes loses control under normal binocular vision

Front 8

tropia

Back 8

fusion control not present

Front 9

comitant

Back 9

size of deviation does not vary more than a few PD with direction of gaze OR with the eye used for fixating

Front 10

incomitant

Back 10

noncomitant, varies with gaze or with eye used

Front 11

ddx of incomitant

Back 11

most commonly paralytic or restrictive condition

Front 12

diplopia in TED, comitant or incomitant?

Back 12

most likely incomitant due to restriction (would vary PD in gazes)

Front 13

6n palsy, comitant or incomitant?

Back 13

incomitant, due to palsy

Front 14

spontaneously fixates from one eye to the other

Back 14

alternating fixation

Front 15

definite preference for fixation with one eye

Back 15

monocular fixation

Front 16

Age cut-off for "congenital" strabismus

Back 16

6 months.
A deviation documented before age 6 months, presumably related to a defect present at birth; the term infantile might be more appropriate.

Acquired: a devaiation with later onset, after a period of apparently normal visual development.

Front 17

Acquired strabismus

Back 17

Acquired

A deviation documented before age 6 months, presumably related to a defect present at birth; the term infantile might be more appropriate.

Acquired: a devaiation with later onset, after a period of apparently normal visual development.

Front 18

An infant presents at 9mos old with an esotropia. The parents first noticed it when he was 4 months old. Congenital or acquired?

Back 18

congenital?

A congenital deviation documented before age 6 months, presumably related to a defect present at birth; the term infantile might be more appropriate.

Acquired: a devaiation with later onset, after a period of apparently normal visual development.

Front 19

Optical axis

Back 19

The optical axis is a line that passes through the optical center of the cornea, lens, and fovea (best approximation)

The Pupillary axis is an imaginary line that passes perpendicular to corneal surface through the midpoint of the entrance to the pupil

The visual axis is the line between the fixation point and the fovea.

Front 20

pupillary axis

Back 20

The optical axis is a line that passes through the optical center of the cornea, lens, and fovea (best approximation)

The Pupillary axis is an imaginary line that passes perpendicular to corneal surface through the midpoint of the entrance to the pupil

The visual axis is the line between the fixation point and the fovea.

Front 21

visual axis

Back 21

The optical axis is a line that passes through the optical center of the cornea, lens, and fovea (best approximation)

The Pupillary axis is an imaginary line that passes perpendicular to corneal surface through the midpoint of the entrance to the pupil

The visual axis is the line between the fixation point and the fovea.

Front 22

How many extraocular muscles?

Back 22

4 recti, 2 oblique, 1 levator = 7

Front 23

which muscles does CNIII innervate?

Back 23

levator, SR, IR, MR

upper division levator and SR
lower division MR, IR, IO
parasympathetic on the lower branch that supplies the IO

Front 24

which muscles do the upper and lower portions of CNIII innervate?

Back 24

upper division levator and SR
lower division MR, IR, IO
parasympathetic on the lower branch that supplies the IO

Front 25

Which branch of which cranial nerve do the parasympathetics to the sphincter pupillae and ciliary muscle travel?

Back 25

CNIII
upper division levator and SR
lower division MR, IR, IO
parasympathetic on the lower branch that supplies the IO

Front 26

The primary action is defined as the major action of the rectus muscles in primary position (head straight, eyes straight). In what position are the secondary and tertiary actions defined?

Back 26

Also in the primary position, the additional effects of those muscles when the globe Is in primary position.

Front 27

How far in degrees can the globe be moved from the primary position? How far does it normal circumstances before head movemet occurs?

Back 27

The eyes can rotate 50 degrees in each direction usually, but normally the eyes will rotate only 15-20 deg before head movement occurs

Front 28

Which EOM do NOT originate from the annulus of zinn?

Back 28

levator, superior oblique, and inferior oblique do not originate from the annulus of zinn.

The levator originates at the apex of the orbit from the LESSER wing of the sphenoid bone just SUPERIOR to the annulus of zinn; blends with the SR and SO as well, and the fascial sheaths of the SR are connected. It becomes an aponeurosis in the region of the superior fornix. This muscle has BOTH a cutaneous and tarsal insertion.

The Superior oblique muscle originates from the orbital apex ABOe the annulus of zinn and passes anteriorly and upward along the superomedial wall of the orbit. The muscle becomes tendinous before passing through the trochlea, a cartilaginous saddle attached to the frontal bone in the superior nasal orbit. The trochlea redirects it inferior, lateral, and posteriorly to form a 51 degree angle with the visual axis in primary position. The tendon enetrates the tenon capsule 2mm nasally and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under the SR, the tendon inserts in the posterosuperior quadrant of the eyball, almost entirely laterally to the midvertical plane.

The inferior oblique muscle originates medially from the periosteum of the maxillary bone, just posterior to the orbital rim and lateral to the orifice of the lacrimal fossa. Travels INFERIOR to the inferior rectus muscle (both obliques inferior to rectus muscles). It also forms a 51deg angle with the visual axis.

Front 29

Which EOM attaches to the maxillary periosteum?

Back 29

Inferior oblique

levator, superior oblique, and inferior oblique do not originate from the annulus of zinn.

The levator originates at the apex of the orbit from the LESSER wing of the sphenoid bone just SUPERIOR to the annulus of zinn; blends with the SR and SO as well, and the fascial sheaths of the SR are connected. It becomes an aponeurosis in the region of the superior fornix. This muscle has BOTH a cutaneous and tarsal insertion.

The Superior oblique muscle originates from the orbital apex ABOe the annulus of zinn and passes anteriorly and upward along the superomedial wall of the orbit. The muscle becomes tendinous before passing through the trochlea, a cartilaginous saddle attached to the frontal bone in the superior nasal orbit. The trochlea redirects it inferior, lateral, and posteriorly to form a 51 degree angle with the visual axis in primary position. The tendon enetrates the tenon capsule 2mm nasally and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under the SR, the tendon inserts in the posterosuperior quadrant of the eyball, almost entirely laterally to the midvertical plane.

The inferior oblique muscle originates medially from the periosteum of the maxillary bone, just posterior to the orbital rim and lateral to the orifice of the lacrimal fossa. Travels INFERIOR to the inferior rectus muscle (both obliques inferior to rectus muscles). It also forms a 51deg angle with the visual axis.

Front 30

A patient is undergoing ethmoid sinus surgery, what EOM is at risk?

Back 30

The horizontal rectus muscles are the medial and lateral rectus muscles. Both arise from
the annulus of Zinn. The medial rectus muscle courses along the medial orbital wall. The
proximity of the medial rectus muscle to the medial orbital wall means the medial rectus
can be injured during ethmoid sinus surgery. The medial rectus muscle is the only rectus muscle that does not have an oblique muscle running tangential to it. This makes surgery on the medial rectus
less complicated, but means that there is neither a point of reference if the surgeon becomes
disoriented nor a point of attachment if the muscle is lost.

Front 31

Which is the only recti muscle without a corresponding oblique running tangential to it?

Back 31

Medial rectus

The horizontal rectus muscles are the medial and lateral rectus muscles. Both arise from
the annulus of Zinn. The medial rectus muscle courses along the medial orbital wall. The
proximity of the medial rectus muscle to the medial orbital wall means the medial rectus
can be injured during ethmoid sinus surgery. The medial rectus muscle is the only rectus muscle that does not have an oblique muscle running tangential to it. This makes surgery on the medial rectus
less complicated, but means that there is neither a point of reference if the surgeon becomes
disoriented nor a point of attachment if the muscle is lost.

Front 32

Where do the vertical recti originate?

Back 32

The superior rectus
muscle originates from the annulus of Zinn and courses anteriorly, upward over the
eyeball, and laterally, forming an angle of 23° with the visual axis of the eye in primary
position (Fig 2-1; see also Chapter 3, Fig 3-4). In primary position, this muscle's primary
action is elevation, secondary action is intorsion (incycloduction), and tert iary action is
adduction.
The inferior rectus muscle also arises from the annulus ofZinn, and it then courses anteriorly,
downward, and laterally along the tloor of the orbit, forming an angle of23° wi th
the visual axis of the eye in primary position (see Chapter 3, Fig 3-5). In primary position,
the inferior rectus muscle's primary action is depression, secondary action is extorsion
(excycloduction), and tertiar}' action is adduction.

Front 33

What angle do the vertical recti form with the visual axis?

Back 33

23 deg
The superior rectus
muscle originates from the annulus of Zinn and courses anteriorly, upward over the
eyeball, and laterally, forming an angle of 23° with the visual axis of the eye in primary
position (Fig 2-1; see also Chapter 3, Fig 3-4). In primary position, this muscle's primary
action is elevation, secondary action is intorsion (incycloduction), and tert iary action is
adduction.
The inferior rectus muscle also arises from the annulus ofZinn, and it then courses anteriorly,
downward, and laterally along the tloor of the orbit, forming an angle of23° wi th
the visual axis of the eye in primary position (see Chapter 3, Fig 3-5). In primary position,
the inferior rectus muscle's primary action is depression, secondary action is extorsion
(excycloduction), and tertiar}' action is adduction.

Front 34

What are the primary, secondary, and tertiary actions of the superior rectus?

Back 34

this muscle's primary
action is elevation, secondary action is intorsion (incycloduction), and tert iary action is
adduction.

The superior rectus
muscle originates from the annulus of Zinn and courses anteriorly, upward over the
eyeball, and laterally, forming an angle of 23° with the visual axis of the eye in primary
position (Fig 2-1; see also Chapter 3, Fig 3-4). In primary position, this muscle's primary
action is elevation, secondary action is intorsion (incycloduction), and tert iary action is
adduction.
The inferior rectus muscle also arises from the annulus ofZinn, and it then courses anteriorly,
downward, and laterally along the tloor of the orbit, forming an angle of23° wi th
the visual axis of the eye in primary position (see Chapter 3, Fig 3-5). In primary position,
the inferior rectus muscle's primary action is depression, secondary action is extorsion
(excycloduction), and tertiar}' action is adduction.

Front 35

Where does the superior oblique run relative to the superior rectus?

Back 35

Below it. All obliques run below the recti

Front 36

What are the primary, secondary, and tertiary actions of the inferior rectus?

Back 36

The inferior rectus muscle also arises from the annulus ofZinn, and it then courses anteriorly,
downward, and laterally along the tloor of the orbit, forming an angle of23° wi th
the visual axis of the eye in primary position (see Chapter 3, Fig 3-5). In primary position,
the inferior rectus muscle's primary action is depression, secondary action is extorsion
(excycloduction), and tertiar}' action is adduction.

Front 37

Describe the course of the superior oblique muscle

Back 37

The superior oblique muscle originates from the orbital apex above the annulus of Zinn
and passes anteriorly and upward along the superomedial wall of the orbit. T he muscle
becomes tendinous before passing through the trochlea, a cartilaginous saddle attached to
the frontal bone in the superior nasal orbit. A bursa-like cleft separates the trochlea from
the loose flbrovascular sheath surrounding the tendon. The discrete fibers of the tendon
telescope as they move through the trochlea, the central fibers moving farther than theperipheral ones (Fig 2-2). The function of the trochlea is to redirect the tendon inferiorly,
posteriorly, and laterally, forming an angle ofSI 0 with the visual axis of the eye in primary
position (see Chapter 3, Fig 3·6). The tendon penetrates the Tenon capsule 2 mm nasally
and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under
the superior rectus muscle, the tendon inserts in the posterosuperior quadrant of the eyeball,
almost or entirely laterally to the midvertical plane or center of rotation. In primary
position, the primary action of the superior oblique muscle is intorsion (incydoduction),
secondary action is depression, and tertiary action is abduction.

Front 38

What separates the trochlea from the loose fibrovascular sheath surrounding the tendon?

Back 38

Bursa-like cleft

peripheral ones (Fig 2-2). The function of the trochlea is to redirect the tendon inferiorly,
posteriorly, and laterally, forming an angle ofSI 0 with the visual axis of the eye in primary
position (see Chapter 3, Fig 3·6). The tendon penetrates the Tenon capsule 2 mm nasally
and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under
the superior rectus muscle, the tendon inserts in the posterosuperior quadrant of the eyeball,
almost or entirely laterally to the midvertical plane or center of rotation. In primary
position, the primary action of the superior oblique muscle is intorsion (incydoduction),
secondary action is depression, and tertiary action is abduction.

Front 39

Which fibers of the superior oblique tendons move farther as they telescope through the trochlea?

Back 39

The central fibers

Front 40

What 3 directions is the superior oblique tendon redirected by the trochlea?

Back 40

inferiorly, laterally, posteriorly, forming a 51 deg angle with the visual axis in the eye in primary position

Front 41

Where does the superior oblique tendon penetrate?

Back 41

The function of the trochlea is to redirect the tendon inferiorly,
posteriorly, and laterally, forming an angle ofSI 0 with the visual axis of the eye in primary
position (see Chapter 3, Fig 3·6). The tendon penetrates the Tenon capsule 2 mm nasally
and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under
the superior rectus muscle, the tendon inserts in the posterosuperior quadrant of the eyeball,
almost or entirely laterally to the midvertical plane or center of rotation.

Front 42

What angle is formed with the visual axis of the eye in primary position by the oblique muscles?

Back 42

The function of the trochlea is to redirect the tendon inferiorly,
posteriorly, and laterally, forming an angle ofSI 0 with the visual axis of the eye in primary
position (see Chapter 3, Fig 3·6). The tendon penetrates the Tenon capsule 2 mm nasally
and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under
the superior rectus muscle, the tendon inserts in the posterosuperior quadrant of the eyeball,
almost or entirely laterally to the midvertical plane or center of rotation.

Front 43

Where does the SO tendon penetrate the tenons capsule?

Back 43

The function of the trochlea is to redirect the tendon inferiorly,
posteriorly, and laterally, forming an angle ofSI 0 with the visual axis of the eye in primary
position (see Chapter 3, Fig 3·6). The tendon penetrates the Tenon capsule 2 mm nasally
and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under
the superior rectus muscle, the tendon inserts in the posterosuperior quadrant of the eyeball,
almost or entirely laterally to the midvertical plane or center of rotation.

Front 44

What quadrant does the SO insert, and where does the tendon penetrate the tenons capsule relative to the superior rectus muscle?

Back 44

The function of the trochlea is to redirect the tendon inferiorly,
posteriorly, and laterally, forming an angle ofSI 0 with the visual axis of the eye in primary
position (see Chapter 3, Fig 3·6). The tendon penetrates the Tenon capsule 2 mm nasally
and 5 mm posteriorly to the nasal insertion of the superior rectus muscle. Passing under
the superior rectus muscle, the tendon inserts in the posterosuperior quadrant of the eyeball,
almost or entirely laterally to the midvertical plane or center of rotation.

Front 45

what are the primary, secondary, and tertiary actions of the superior oblique

Back 45

In primary
position, the primary action of the superior oblique muscle is intorsion (incydoduction),
secondary action is depression, and tertiary action is abduction.

Front 46

Where does the IO originate?

Back 46

The inferior oblique muscle originates from the periosteum of the maxillary bone, just
posterior to the orbital rim and lateral to the orifice of the lacrimal fossa. It passes later·
ally, superiorly, and posteriorly, going inferior to the inferior rectus muscle and inserting
under the lateral rectus muscle in the posterolateral portion of the globe, in the area of the
macula. The inferior oblique muscle forms an angle of 5 1° with the visual axis of the eye
in primary position (see Chapter 3, Fig 3-7). In primary position, the muscle's primary
action is extorsion (excycloduction), secondary action is elevation, and tertiary action is
abduction.

Front 47

Describe the course of the IO

Back 47

The inferior oblique muscle originates from the periosteum of the maxillary bone, just
posterior to the orbital rim and lateral to the orifice of the lacrimal fossa. It passes later·
ally, superiorly, and posteriorly, going inferior to the inferior rectus muscle and inserting
under the lateral rectus muscle in the posterolateral portion of the globe, in the area of the
macula. The inferior oblique muscle forms an angle of 5 1° with the visual axis of the eye
in primary position (see Chapter 3, Fig 3-7). In primary position, the muscle's primary
action is extorsion (excycloduction), secondary action is elevation, and tertiary action is
abduction.

Front 48

What angle is formed by the inferior oblique muscle with the visual axis?

Back 48

The inferior oblique muscle originates from the periosteum of the maxillary bone, just
posterior to the orbital rim and lateral to the orifice of the lacrimal fossa. It passes later·
ally, superiorly, and posteriorly, going inferior to the inferior rectus muscle and inserting
under the lateral rectus muscle in the posterolateral portion of the globe, in the area of the
macula. The inferior oblique muscle forms an angle of 5 1° with the visual axis of the eye
in primary position (see Chapter 3, Fig 3-7). In primary position, the muscle's primary
action is extorsion (excycloduction), secondary action is elevation, and tertiary action is
abduction.

Front 49

Where is the origin of the levator?

Back 49

The levator palpebrae supcrioris muscle arises at the apex of the orbit from the lesser
wing of the sphenoid bone just superior to the annulus of zinn. The origin of this muscle
blends with the superior rectus muscle inferiorly and with the superior oblique muscle
medially. The levator palpebrae superioris passes anteriorly, lying just above the superior
rcctlls muscle; the fascial sheaths of these 2 muscles arc connected. The levator palpebrae superioris muscle becomes an aponeurosis in the region of the superior fornix. This muscle
has both a cutaneous and a tarsal insertion.

Front 50

Which two muscles doe the levator origins blend with?

Back 50

The levator palpebrae supcrioris muscle arises at the apex of the orbit from the lesser
wing of the sphenoid bone just superior to the annulus of zinn The origin of this muscle
blends with the superior rectus muscle inferiorly and with the superior oblique muscle
medially. The levator palpebrae superioris passes anteriorly, lying just above the superior
rcctlls muscle; the fascial sheaths of these 2 muscles arc connected. The levator palpebrae superioris muscle becomes an aponeurosis in the region of the superior fornix. This muscle
has both a cutaneous and a tarsal insertion.

Front 51

Which EOM is the levators fascial sheath connected to?

Back 51

The levator palpebrae supcrioris muscle arises at the apex of the orbit from the lesser
wing of the sphenoid bone. just superior to the annulus of zinn. The origin of this muscle
blends with the superior rectus muscle inferiorly and with the superior oblique muscle
medially. The levator palpebrae superioris passes anteriorly, lying just above the superior
rcctlls muscle; the fascial sheaths of these 2 muscles arc connected. The levator palpebrae superioris muscle becomes an aponeurosis in the region of the superior fornix. This muscle
has both a cutaneous and a tarsal insertion.

Front 52

where does the levator become an aponeurosis?

Back 52

superior fornix
The levator palpebrae supcrioris muscle arises at the apex of the orbit from the lesser
wing of the sphenoid bone. just superior to the annulus of zinn. The origin of this muscle
blends with the superior rectus muscle inferiorly and with the superior oblique muscle
medially. The levator palpebrae superioris passes anteriorly, lying just above the superior
rcctlls muscle; the fascial sheaths of these 2 muscles arc connected. The levator palpebrae superioris muscle becomes an aponeurosis in the region of the superior fornix. This muscle
has both a cutaneous and a tarsal insertion.

Front 53

What is the shortest length of ACTIVE muscle?

Back 53

SO 32mm (turns into tendon)
IO 37mm
recti and levator 40mm

Front 54

Where is the functional origin of the trochlea

Back 54

FUNCTIONAL at trochlea
anatomical orb apex above annulus of zinn

Front 55

Which muscles have a direction of pull 90 deg to the visual axis? 23deg? 51 deg?

Back 55

horz Recti, vert recti, obliques

Front 56

Which EOM has the longest tendon? Shortest? Which recti has the shortest tendon?

Back 56

SO 26mm
IO 1
MR 4.5

Front 57

arc of contact

Back 57

skipped, table 2-1

Front 58

Lower CN III innervates which muscles?
Upper?

Back 58

MR, IR, IO
SR, Lev

Front 59

find mnemonic for the primary, secondary, tertiary actions of the EOMS

Back 59

yes

Front 60

anatomical insertions of
SO
IO
Lev

Back 60

posterior to equator in superotemporal quadrant
macular area
septa of pretarsal orbic and anterior tarsus

Front 61

tertiary action of both obliques?

Back 61

abduct
primary torsion
secondary elev/depr

Front 62

abd/adduction always tertiary?

Back 62

YES (except horz recti - this is only fxn)
Recti all ADductt in tertiary
(obliques ABduct)

Front 63

secondary action of superior rectus? inferior rectus?

Back 63

SUPERIOR all intort
Inferior all extort (obliques primary = torsion)

Front 64

How far from the limbus does the MR attach?

Back 64

Starting at the medial rectus and proceeding to inferior rectus, lateral rectus, and superior
rectus muscles, the rectus muscle tendons insert progressively farther from the limbus. A
continuous curve drawn through these insertions yields a spiral, known as the spiral of
Til/nux (Fig 2-4). The temporal side of the ve rtical rectus muscle insertion is farther from
the limbus (ie, more posterior) than is the nasal side.

Front 65

How far from the limbus does the Lateral rectus? attach?

Back 65

Starting at the medial rectus and proceeding to inferior rectus, lateral rectus, and superior
rectus muscles, the rectus muscle tendons insert progressively farther from the limbus. A
continuous curve drawn through these insertions yields a spiral, known as the spiral of
Til/nux (Fig 2-4). The temporal side of the ve rtical rectus muscle insertion is farther from
the limbus (ie, more posterior) than is the nasal side.

Front 66

How far does the lateral rectus? superior rectus att from limbus?

Back 66

Starting at the medial rectus and proceeding to inferior rectus, lateral rectus, and superior
rectus muscles, the rectus muscle tendons insert progressively farther from the limbus. A
continuous curve drawn through these insertions yields a spiral, known as the spiral of
Til/nux (Fig 2-4). The temporal side of the ve rtical rectus muscle insertion is farther from
the limbus (ie, more posterior) than is the nasal side.

Front 67

which side of which EOMs insert progressively farther from the limbus?

Back 67

The temporal side of the vertical rectus muscle insertion is farther from
the limbus (ie, more posterior) than is the nasal side.

Front 68

What artery supposed the most important blood supply to the eoms?

Back 68

The muscular branches of the ophthalmic artery provide the most important blood supply
for the extraocular muscles. The lateml muswlar branch supplies the lateral rectus,
superior rectus, superior oblique, and levator palpebrae superioris muscles; the medial
muscular branch, the larger of the 2, supplies the inferior rectus, medial reclus, and inferior
oblique muscles.

Front 69

What muscles does the lateral muscular branch of the ophthalmic artery provide?

Back 69

The muscular branches of the ophthalmic artery provide the most important blood supply
for the extraocular muscles. The lateml muswlar branch supplies the lateral rectus,
superior rectus, superior oblique, and levator palpebrae superioris muscles; the medial
muscular branch, the larger of the 2, supplies the inferior rectus, medial reclus, and inferior
oblique muscles.

Front 70

What muscles does the medial muscular branch of the ophthalmic artery provide?

Back 70

The muscular branches of the ophthalmic artery provide the most important blood supply
for the extraocular muscles. The lateml muswlar branch supplies the lateral rectus,
superior rectus, superior oblique, and levator palpebrae superioris muscles; the medial
muscular branch, the larger of the 2, supplies the inferior rectus, medial reclus, and inferior
oblique muscles.

Front 71

What EOM is partially supplied by the lacrimal artery?

Back 71

The lateral reclus muscle is partially suppli ed by the lacrimal artery; the infraor/Jital
artery partially supplies the inferior oblique and inferior reclus muscles. The muscular
branches give rise to the a11terior ciliary arteries accompanying the rectus muscles; each
rectus muscle has 1 to 3 anterior ciliary arteries. These pass to the episclera of the globe and then supply blood to the anterior segment. The superior and inferior rectus muscles
carry the bulk of the blood supply.

Front 72

The infraorbital artery partially supplies which EOMs?

Back 72

The lateral reclus muscle is partially suppli ed by the lacrimal artery; the infraor/Jital
artery partially supplies the inferior oblique and inferior reclus muscles. The muscular
branches give rise to the a11terior ciliary arteries accompanying the rectus muscles; each
rectus muscle has 1 to 3 anterior ciliary arteries. These pass to the episclera of the globe and then supply blood to the anterior segment. The superior and inferior rectus muscles
carry the bulk of the blood supply.

Front 73

The muscular branches give rise to _______________ arteries that accompany the rectus muscles, each with 1-3 of these. These also provide blood supply to which part of the eye?

Back 73

anterior ciliary arteries
The lateral reclus muscle is partially suppli ed by the lacrimal artery; the infraor/Jital
artery partially supplies the inferior oblique and inferior reclus muscles. The muscular
branches give rise to the a11terior ciliary arteries accompanying the rectus muscles; each
rectus muscle has 1 to 3 anterior ciliary arteries. These pass to the episclera of the globe and then supply blood to the anterior segment. The superior and inferior rectus muscles
carry the bulk of the blood supply.

Front 74

Where does the venous blood drain from the EOMs?

Back 74

The venous system parallels the arterial system, emptying into the superior and inferior
orbital veins. Generally, 4 vortex veins are located posterior to the equator; these are usually
found near the nasal and temporal margins of the superior rectus and inferior rectus
muscles.

Front 75

Where are the 4 vortex veins located?

Back 75

The venous system parallels the arterial system, emptying into the superior and inferior
orbital veins. Generally, 4 vortex veins are located posterior to the equator; these are usually
found near the nasal and temporal margins of the superior rectus and inferior rectus
muscles.

Front 76

Are the eye muscles fast or slow? fatigue prone or fatigue resistant?

Back 76

The important functional characteristics of muscle fibers are contraction speed and fatigue
resistance. The eye muscles participate in motor acts that are among the fastest (saccadic
eye movements) in the body and in those that are among the most sustained (gaze
fixation and vergence movements). Like skeletal muscle, extraocular muscle is voluntary
striated muscle. However, developmentally, biochemically, structurally, and functionally,
it is different from typical skeletal muscle. The extraocular muscles are innervated at a
ratio of nerve fiber to muscle fiber up to 10 times that of skeletal muscle. This difference
may allow for more accurate e)'e movements controlled by an array of systems ranging
from the primitive vestibulo-ocular reflex to highly evolved vergence movements.

Front 77

ratio of nerve fibers to muscle fibers compared to skeletal muscle? What might this do for eye movements?

Back 77

The important functional characteristics of muscle fibers are contraction speed and fatigue
resistance. The eye muscles participate in motor acts that are among the fastest (saccadic
eye movements) in the body and in those that are among the most sustained (gaze
fixation and vergence movements). Like skeletal muscle, extraocular muscle is voluntary
striated muscle. However, developmentally, biochemically, structurally, and functionally,
it is different from typical skeletal muscle. The extraocular muscles are innervated at a
ratio of nerve fiber to muscle fiber up to 10 times that of skeletal muscle. This difference
may allow for more accurate e)'e movements controlled by an array of systems ranging
from the primitive vestibulo-ocular reflex to highly evolved vergence movements.

Front 78

What are the layers of the extraocular muscles?

Back 78

The extraocular muscles exhibit a distinct 2-layer organization: an outer orbital layer,
which acts only on connective tissue pulleys (see the section Pulley System), and an inner
global layer, whose tendon inserts on the sclera to move the globe. The muscle fibers compris
ing t·he orbital and global layers can be either singly or multiply innervated.

Front 79

What function do the two different layers of the EOMs provide

Back 79

The extraocular muscles exhibit a distinct 2-layer organization: an outer orbital layer,
which acts only on connective tissue pulleys (see the section Pulley System), and an inner
global layer, whose tendon inserts on the sclera to move the globe. The muscle fibers compris
ing t·he orbital and global layers can be either singly or multiply innervated.

Front 80

are these layers singly or multiply innervated?

Back 80

The extraocular muscles exhibit a distinct 2-layer organization: an outer orbital layer,
which acts only on connective tissue pulleys (see the section Pulley System), and an inner
global layer, whose tendon inserts on the sclera to move the globe. The muscle fibers compris
ing t·he orbital and global layers can be either singly or multiply innervated.

Front 81

Which (singly or multiply innervated fibers) are fast twitch?

Back 81

Singly innervated fibers arc fast -twitch generating and resistant to fatigue. Eighty percent
of the fibers comprising the orbital layer muscle are s ingly innervated. Ninety percent
CHAPTER 2: Anatomy of the Extraocular Muscles and Their Fascia • 19
of the fibers making up the global layer muscle a re singly inne rvated, and they can be
subdivided into 3 groups (red, intermediate, and white), based on mitochondrial content,
with the red fibers being the most fatigue resistant and the white fibers, the least. The orbital
singly innervated fibers a re considered the major contributor to sustained extraocular
muscle force in prima ry and deviated posi tions, and, of all muscle fiber types, this type
is the most affected by denervation from damage to the motor ne rves or from damage to
the end plates, occurring after botulinum toxin injection.

Front 82

What percent of orbital layer is fast twitch (singly innervated)? global layer?

Back 82

Singly innervated fibers arc fast -twitch generating and resistant to fatigue. Eighty percent
of the fibers comprising the orbital layer muscle are s ingly innervated. Ninety percent
CHAPTER 2: Anatomy of the Extraocular Muscles and Their Fascia • 19
of the fibers making up the global layer muscle a re singly inne rvated, and they can be
subdivided into 3 groups (red, intermediate, and white), based on mitochondrial content,
with the red fibers being the most fatigue resistant and the white fibers, the least. The orbital
singly innervated fibers a re considered the major contributor to sustained extraocular
muscle force in prima ry and deviated posi tions, and, of all muscle fiber types, this type
is the most affected by denervation from damage to the motor ne rves or from damage to
the end plates, occurring after botulinum toxin injection.

Front 83

Which of the three groups of fibers making up the global layer, red, intermediate, or white) has the most mitochondrial content? Which are the fastest fatiguing?

Back 83

White

Singly innervated fibers arc fast -twitch generating and resistant to fatigue. Eighty percent
of the fibers comprising the orbital layer muscle are s ingly innervated. Ninety percent
CHAPTER 2: Anatomy of the Extraocular Muscles and Their Fascia • 19
of the fibers making up the global layer muscle a re singly inne rvated, and they can be
subdivided into 3 groups (red, intermediate, and white), based on mitochondrial content,
with the red fibers being the most fatigue resistant and the white fibers, the least. The orbital
singly innervated fibers a re considered the major contributor to sustained extraocular
muscle force in prima ry and deviated posi tions, and, of all muscle fiber types, this type
is the most affected by denervation from damage to the motor ne rves or from damage to
the end plates, occurring after botulinum toxin injection.

Front 84

Which, orbital or global, singly or multiply, innervated fibers are the major contributor to sustained extraoular force in primary and deviated positions? Which type is most affected by denervation from damage to motor nerves or /botulinum?

Back 84

The orbital
singly innervated fibers a re considered the major contributor to sustained extraocular
muscle force in prima ry and deviated posi tions, and, of all muscle fiber types, this type
is the most affected by denervation from damage to the motor ne rves or from damage to
the end plates, occurring after botulinum toxin injection.

Front 85

What is the function of the multiply innervated ibers of the orbital and global layers?

Back 85

The function of the multiply innervated fibers of the orbital and global layers is not
clear. These fibers are not seen in the levator palpebrae superioris, and it is thought that
they a re involved in the finer control of fixation and in the smooth and finely graded eye
movements, particularly vergence control.

Front 86

Which layer actually attaches to the globe?

Back 86

Inner global layer
The extraocular muscles exhibit a distinct 2-layer organization: an outer orbital layer,
which acts only on connective tissue pulleys (see the section Pulley System), and an inner
global layer, whose tendon inserts on the sclera to move the globe. The muscle fibers compris
ing t·he orbital and global layers can be either singly or multiply innervated.

Front 87

Which layer interacts only with the connective tissue pulley?

Back 87

The extraocular muscles exhibit a distinct 2-layer organization: an outer orbital layer,
which acts only on connective tissue pulleys (see the section Pulley System), and an inner
global layer, whose tendon inserts on the sclera to move the globe. The muscle fibers compris
ing t·he orbital and global layers can be either singly or multiply innervated.

Front 88

Are the musculofibroelastic structure suspending the globe, supporting the EOMs and compartmentalizing the fat pads distinct or more complexly interconnected?

Back 88

vVith i n the orbit, a complex musculofibroelastic structure suspends the globe, supports the
extraocular muscles, and compartmentalizes the fat pads (Fig 2-5). In the past, the disti nctness
of these layers has been overstated. The extent and complexi ty of the interconnectedness
of the orbital tissues has recently come to light and is still being investigated. Cli nically,
the consequences of tissue entrapment in blowout fractures and post-retrobulbar hemorrhage
fibrosis of delicate fi brous septa illustrate the intense fibrous connections throughout
the orbit.

Front 89

What clinical entities illustrates this interconnectedness of the fibrous tissue in the orbit?

Back 89

consequences of tissue entrapment in blowout fractures and post-retrobulbar fibrosis of the delicate fibrous septa

Front 90

How far does the fatty tissue of the orbit come forward relative to the limbus?

Back 90

The eye is supported and cushioned in the orbit by a large amount of fatty tissue. External
to the muscle cone, fatty tissue comes forward with the rectus muscles, stopping about
10 rnm from the .lirnbus. Fatty tissue is a.lso present inside the muscle cone, kept away from
the sclera by the Tenon capsule (see Fig 2-5).

Front 91

What separates the fatty tissue inside the muscle cone from the sclera?

Back 91

Tenon's capsule

The eye is supported and cushioned in the orbit by a large amount of fatty tissue. External
to the muscle cone, fatty tissue comes forward with the rectus muscles, stopping about
10 rnm from the .lirnbus. Fatty tissue is a.lso present inside the muscle cone, kept away from
the sclera by the Tenon capsule (see Fig 2-5).

Front 92

At what point is the fascial capsule surrounding the rectus muscle the thint? Where do they thicken? What happens anteriorly?

Back 92

posteriorly thin, thicken near the equator as they pass through the sleeve of tenon capsule, anteriorly the undersurface of the muscle and sclera there is almost no fascia only a CT footplate that connects the muscle to the globe.

Each rectus muscle has a surrounding fascial capsule that extends with the muscle from
its origin to its insertion. These capsules are thin posteriorly, but near the equator they
thicken as they pass through the sleeve of the Tenon capsule, continuing anteriorly with the muscles to their insertions. Anterior to the equator between the undersurface of the
muscle and the sclera there is almost no fascia, only connective tissue footplates that connect
the muscle to the globe. The smooth avascular surface of the muscle capsule allows
the muscles to slide smoothly over the globe.

Front 93

What allows the muscle to glide smoothly over the globe?

Back 93

smooth avascular suface of the muscle capsule

the muscles to their insertions. Anterior to the equator between the undersurface of the
muscle and the sclera there is almost no fascia, only connective tissue footplates that connect
the muscle to the globe. The smooth avascular surface of the muscle capsule allows
the muscles to slide smoothly over the globe.

Front 94

What is the principal orbital fascia forming the envelope within which the eyeball moves?

Back 94

The Tenon capsule (fascia bulbi) is the principal orbital fascia and forms the envelope
within which the eyeball moves (Fig 2-6/\). The Tenon capsule fuses posteriorly with the
optic nerve sheath and fuses anteriorly with the intermuscular septum at a position 3 mm
from the limbus (Fig 2-6B). The posterior portion of the Tenon capsule is thin and flexible,
allowing for free movement of the optic nerve, ciliary nerves, and ciliary vessels as the
globe rotates, while separating the orbital fat inside the muscle cone from the scle ra.

Front 95

Where does the tenon capsule fuse posteriorly and anteriorly respectively?

Back 95

The Tenon capsule (fascia bulbi) is the principal orbital fascia and forms the envelope
within which the eyeball moves (Fig 2-6/\). The Tenon capsule fuses posteriorly with the
optic nerve sheath and fuses anteriorly with the intermuscular septum at a position 3 mm
from the limbus (Fig 2-6B). The posterior portion of the Tenon capsule is thin and flexible,
allowing for free movement of the optic nerve, ciliary nerves, and ciliary vessels as the
globe rotates, while separating the orbital fat inside the muscle cone from the scle ra.

Front 96

Is the posterior portion of tenons capsule thin and flexible or thick and inflexible? What advantage does this give?

Back 96

The Tenon capsule (fascia bulbi) is the principal orbital fascia and forms the envelope
within which the eyeball moves (Fig 2-6/\). The Tenon capsule fuses posteriorly with the
optic nerve sheath and fuses anteriorly with the intermuscular septum at a position 3 mm
from the limbus (Fig 2-6B). The posterior portion of the Tenon capsule is thin and flexible,
allowing for free movement of the optic nerve, ciliary nerves, and ciliary vessels as the
globe rotates, while separating the orbital fat inside the muscle cone from the scle ra.

Front 97

Is the tenons tissue thick and tough or thin and flexible at and just posterior to the globe? What function does this serve?

Back 97

At and
just posterior to the equator, the Tenon capsule is thick and tough, suspending the globe
like a trampoline by means of connections to the periorbital tissues. The global layer of
the 4 rectus muscles penetrates this thick musculofibroelastic tissue approximately 10 mm
posterior to their inse rt ions. The oblique muscles penetrate the Tenon capsule anterior to
the equator. The Tenon capsule continues forward over these 6 extraocular muscles and
separates them from the orbital fat and structures lying outside the muscle cone.

Front 98

What layer of the rectus muscles penetrates the tenons and attaches to the globe? At what distance (recti) relative to what location?

Back 98

The global layer of
the 4 rectus muscles penetrates this thick musculofibroelastic tissue approximately 10 mm
posterior to their inse rt ions. The oblique muscles penetrate the Tenon capsule anterior to
the equator. The Tenon capsule continues forward over these 6 extraocular muscles and
separates them from the orbital fat and structures lying outside the muscle cone.

Front 99

At what distances do the oblique muscles penetrate tenon's capsule and which side of the equator?

Back 99

The global layer of
the 4 rectus muscles penetrates this thick musculofibroelastic tissue approximately 10 mm
posterior to their inse rt ions. The oblique muscles penetrate the Tenon capsule anterior to
the equator. The Tenon capsule continues forward over these 6 extraocular muscles and
separates them from the orbital fat and structures lying outside the muscle cone.

Front 100

What does the tenons capsule separate the EOMs from in the anterior orbit?

Back 100

orbital fat and structures lying outside the muscle cone. The global layer of
the 4 rectus muscles penetrates this thick musculofibroelastic tissue approximately 10 mm
posterior to their inse rt ions. The oblique muscles penetrate the Tenon capsule anterior to
the equator. The Tenon capsule continues forward over these 6 extraocular muscles and
separates them from the orbital fat and structures lying outside the muscle cone.

Front 101

What maintains the position of the extraocular muscles relative to the orbit?

Back 101

The 4 rectus muscles are surrounded by distinct fibroelastic pulleys. Though not as distinct
as the lwchlea of the superior oblique, these pulleys maintain the position of the extraocu·
lar muscles relative to the orbit. They consist of collagen, elast in, and smooth muscle, which
allows them to contract and relax. As the orbital muscle layer contracts, this pulley must be
pulled back so that the distance between the location of the pulley and the insertion of the
muscle on the globe remains approximately constant. just as the trochlea acts as the functional
origin of the superior oblique muscle, these pulleys act mechanically as the rectus
muscle origins. The pulleys consist of discrete rings of dense collagen, which encircle the
extraocular muscles, transitioning into less substantial but broader collagen sleeves both posteriorly and anteriorly. These sleeves stabilize the muscle path, preventing sideslipping
or movement perpendicular to the muscle axis (Fig 2-7).

Front 102

What 3 things does the does the pulley system consist of? What do these things allow the system to do?

Back 102

The 4 rectus muscles are surrounded by distinct fibroelastic pulleys. Though not as distinct
as the lwchlea of the superior oblique, these pulleys maintain the position of the extraocu·
lar muscles relative to the orbit. They consist of collagen, elast in, and smooth muscle, which
allows them to contract and relax. As the orbital muscle layer contracts, this pulley must be
pulled back so that the distance between the location of the pulley and the insertion of the
muscle on the globe remains approximately constant. just as the trochlea acts as the functional
origin of the superior oblique muscle, these pulleys act mechanically as the rectus
muscle origins. The pulleys consist of discrete rings of dense collagen, which encircle the
extraocular muscles, transitioning into less substantial but broader collagen sleeves both posteriorly and anteriorly. These sleeves stabilize the muscle path, preventing sideslipping
or movement perpendicular to the muscle axis (Fig 2-7).

Front 103

stopped at Pulley system

Back 103

stopped