Pediatrics and Strabismus Vol. 1 Flashcards
What differentiates a phoria from a tropia?
Presence or absence of fusional control
What angle does the inferior oblique muscle form with the visual axis in primary position?
51 degrees
What is the only rectus muscle that does not have an oblique muscle running tangential to it?
Medial rectus
What angle does the superior rectus muscle make with the visual axis?
23 degrees
What is the function of the superior rectus muscle primary, secondary, and tertiary action in primary position?
Primary - elevation Secondary- intorsion Tertiary- adduction
What angle does the inferior rectus muscle form with the visual axis?
23 degrees
What is the function of the inferior rectus muscle primary, secondary, and tertiary action in primary position?
Primary- depression Secondary - extorsion Tertiary- adduction
What is the function of the superior oblique muscle primary, secondary, and tertiary action in primary position?
Primary - intorsion Secondary - depression Tertiary- abduction
What angle does the superior oblique muscle form with the visual axis in primary position?
51 degrees
What is the function of the inferior oblique muscle primary, secondary, and tertiary action in primary
Primary- extorsion Secondary - elevation Tertiary- abduction
Which extraocular muscle has the longest tendon?
Superior oblique (26 mm)
Which extraocular muscle has the shortest tendon?
Inferior oblique (1 mm)
What is the primary arterial supply to the extraocular muscles?
Muscular branches of the ophthalmic artery
What are the two major branches of the muscular branches of the ophthalmic artery?
Medial and lateral muscular branch
What four muscles are supplied by the lateral muscular branch of the ophthalmic artery?
- Lateral rectus 2. Superior rectus 3. Superior oblique 4.Levator palpebrae
What three muscles are supplied by the medial muscular branch of the ophthalmic artery?
- Inferior rectus 2.Medial rectus 3. Inferior oblique
What artery partially supplies the lateral rectus muscle?
Lacrimal artery
What artery partially supplies the inferior rectus and inferior oblique muscle?
Infraorbital artery
Which arteries are carried by each rectus muscle and supply blood to the anterior segment?
Anterior ciliary arteries
Which rectus muscle carry the bulk of the anterior ciliary arteries?
Superior and inferior rectus muscle
What does the venous drainage system of the extraocular muscles drain into?
Superior and inferior orbital veins
What is the posterior attachment of Tenon’s capsule?
Optic nerve sheath
What is the anterior attachment of Tenon’s capsule?
Intermuscular septum (3 mm from the limbus)
Where do the extraocular rectus muscles penetrate Tenon’s capsule?
10 mm posterior to their insertions
What structure separates the extraocular muscles from the orbital fat and structures outside the muscle cone?
Tenon’s capsule
What structure separates the intraconal fat pads from the extraconal fat pads?
Intramuscular septum
What forms Lockwood’s ligament?
Fusion of the muscle capsule of the inferior oblique and inferior rectus muscle
What does Lockwood’s ligament connect to?
Lower eyelid retractors
What structure separates the intraconal orbital fat from the sclera?
Tenon’s capsule
Where does the extraconal orbital fat and anteriorly?
10 mm from the limbus
Approximately how far an instrument must be thrust posterior to the rectus muscles insertion to cause damage to their nerves?
26 mm
Which cranial nerve lies outside the muscle cone and is NOT affected by a retrobulbar block?
CN IV
Which extraocular muscle nerve can also cause pupil abnormalities if damaged?
Nerve to the inferior oblique muscle
Which extraocular muscle surgeries may also cause palpebral fissure changes?
Superior and inferior rectus surgery
What vascular complication must be considered when performing simultaneous surgery on 3 rectus muscles, especially in older patients?
Anterior segment ischemia
What complication may occur if Tenon’s capsule is penetrated 10 mm or more posterior to the limbus?
Prolapse of orbital fat
Where is the sclera the thinnest?
Posterior to the rectus muscle insertions
